Good Practice Guide

Good Practice Guide

Delivering quality homes to happy customers

Good Practice Guide

Contents

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1. Foreword – P4 2. Introduction – P5 3. Managing Quality – P6 4. Seasonal working – P8 5. Foundations – P10 6. Substructures – P16 7. Drainage – P22 8. Suspended ground floors – P26 9. Superstructures – P30 10. Roofs – P48 11. First fix (carpentry, M&E services, drylining, fire stopping and windows) – P72 12. Second fix (carpentry, kitchens, M&E) – P93 13. Finishes – P110 14. Moisture and mould in new homes – P126 15. External works – P128 16. Materials storage, organisation and protection – P129

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Good Practice Guide

1. Foreword & Introduction

Hill Good Practice Guide Hill has established an enviable reputation for the quality of the new homes it builds.

This reputation has resulted in continued recognition through multiple industry awards, including the prestigious WhatHouse?

Housebuilder of the Year Award three times in the last decade, and our status as a 5* housebuilder.

Our reputation for an uncompromising approach to quality has been hard earned, but like all good reputations, it is only as good as our last project and is easily lost.

As our business grows, we face challenges ensuring quality is maintained consistently across all corners of the Group and it is extremely important that best practice is shared.

To assist in delivering consistently high quality across our business, this Good Practice Guide, which establishes clear standards and best practices, should be used as a benchmark across all Hill sites.

I hope this document will be useful to you in maintaining our quality reputation for decades to come.

Andy Hill, OBE Group Chief Executive

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All of us within The Hill Group strive to deliver high-quality new homes, whether large premium-spec homes or smaller affordable homes for social housing providers. Here at Hill, our quality standards are tenure blind, with all of our homes benefitting from robust quality systems and expectations.

The difference between providing average quality and good or exceptional quality typically boils down to the uncompromising standards and attention to detail from our teams.

We have launched this Good Practice Guide to provide clear benchmark examples of good or exemplary works, highlighting what minimum standards we expect at Hill and to rebuff some who might think that such quality is impossible to achieve.

Remember that the quality of the homes we build is not just a ‘production issue’. Delivering quality is very much a team effort and other departments also play an important role in delivering highquality finished homes.

It is recognised that specifications do vary across projects and the homes we build. Good quality is however a universal message and the content of this guide can be applied across all types of developments.

For ease of reference, this guide is divided into recognised key work stages. This should enable the chapters to be applied to relevant subcontractor works packages.

I hope you find this guide useful in delivering quality standards that make you proud to be part of Team Hill.

We should all strive to match the quality standards included in this guide and deliver this consistently across each and every Hill Group project.

Andy Mullins, FCIOB, C.Build E FCABE Group Head of Quality

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Good Practice Guide

3. Managing Quality

The Hill Process

Our process relies on our supply chain to sign off completed work stages that we verify through spot checking. The frequency of verification depends on the criticality of the works in question and our trust in the competence and thoroughness of the subcontractors concerned.

Additionally, we have specific ‘hold point’ inspections that are required to be completed before works can progress beyond that point.

y Structure y Roof y 1st fix y Fire stopping

Hold

These hold point inspections are: 1.

Pre-Plaster

2. Pre-Decoration 3. Final Inspection Commissioning Checklist (FICC) 4. Ready To Move In (RTMI) – applicable on Hill Residential projects only.

y Close up walls and ceilings y Plastering y 2nd fix y Fittings y Decoration y Vinyl floring y Soft flooring y Tiling y Commissioning y Finals

Hold

Hill Residential

Hill have a robust quality control procedure which includes the inspection and recording of constructed works via checklists on a digitised platform. This feeds into the ‘Golden thread of Information’ as evidence that we have constructed the works in accordance with the drawings and specifications.

Hold

Hold

Hold

Pre Plaster

Pre Decoration

Final Inspection Commissioning Checklist (FICC)

Legal Completion

Ready to move in (RTMI)

Design & Build

Practical Completion

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How do you make a difference?

Having a structured quality process only goes so far in delivering quality.

In relation to quality, what sets our best performing managers apart from the rest? y Plan ahead: Think ahead and brush up on your technical knowledge where required prior to each work stage commencing. Engage with sources of help and support where needed. y Briefing: At every opportunity, when a new element of work is underway, meet with the subcontractor and discuss what you expect from them. Run through the design and also any relevant Hill technical policies, this Good Practice Guice, NHBC / LABC technical standards and other sources of guidance. y Benchmarking: Agree with the subcontractor that the works are to only to progress to a preagreed stage, at which point this work is to be inspected by our site manager to ensure that it is of sufficiently high standard. This bar must be set high, as it is to be expected that standards may slip slightly from this over time – so give yourself some headroom. Involve others in this if necessary such as our Quality Team (including M&E) and third party ‘experts’. Remember that NHBC offer a benchmarking inspection at the first key stage inspections. Periodically these benchmark inspections may have to be repeated if quality slippage is observed or if there has been a change of operatives / supervision.

y Create unofficial mini-hold points to ensure that you give yourself early opportunities to intervene should action be needed. A regular gentle ‘touch of the tiller’ will always deliver better results than less frequent major course corrections. Check quality regularly and often. y Set consistently high standards and be a proactive manager rather than a passive, reactive one. Do not accept or turn a blind eye to poor quality work and do not be afraid to implement a zero tolerance and reject or instruct works to be re-built. Make sure your subcontractors know what your high standards are, and the consequences for them if they stray from this. Walk the walk, make a difference and seek support if you need it. y Share best practice and create a winning team culture. Celebrate and praise good work. y Where necessary, escalate issues to senior subcontractor management and don’t forget to make an effort to share praise with them too.

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Good Practice Guide

4. Seasonal working

Working in all different weather conditions is unavoidable, as projects commence and progress at all times of the year and throughout all seasons.

Technical Guidance BQ036 covers ‘Cold Weather Working’ and the necessary precautions needed when working through cold winter months.

It is anticipated that our winters will become milder and wetter and summers hotter and drier in the future, which poses additional challenges.

Weather condition: Cold: Refer to Technical Guidance BQ036 ‘Cold Weather Working.’

Wet: Consider the specification of products or systems as some require dry weatherproof conditions that may be practically impossible to achieve in wet conditions. In some cases products are wholly unsuitable for application in wet conditions (e.g. self-adhesive waterproof tanking membranes or hydrophilic strips). Ensure that materials are stored to prevent them becoming water damaged, excessively wet or contaminated by wet ground.

Walls and insulation should be protected from rainwater to limit the amount of water that is built in to the structure – and that has to subsequently dry out.

Ensure that internal materials are stored and installed in weather tight conditions.

To avoid black mould, ensure that the structure has dried out sufficiently before drylining or applying dot and dab plasterboard (the walls should be <16% moisture content) and provide dehumidifiers, heating and ventilation to assist drying out where required.

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Wind: Wind can damage partially constructed structural elements, sometimes catastrophically.

It can also have an accelerated drying effect on water-based products, which may prevent correct hydration or cause excessive drying shrinkage.

Working time (before a product dries or sets) may also be reduced, causing application issues.

Geography and topography of the site may also play a part as some sites are more exposed to wind than others.

In such cases, temporary screening should be reviewed to mitigate this issue.

Hot weather: Much the same as wind, excessive heat can reduce working time and cause an accelerated drying/curing.

This will however affect works internally and in sheltered areas as well as external works.

In many cases, product manufacturers do not endorse application of products in direct summer sunlight and screening may be required.

Substrates may need to be wetted if they have become too dry, to avoid excessive suction of moisture from subsequent applications (e.g. plaster or render), preventing correct hydration.

Paint and surface finishes may dry too quickly and may require thinning to aid workability. Manufactures instructions should always be followed when thinning products.

Short days: Some processes require time for a partial set/cure to occur prior to finishing (e.g. pointing a wet verge). On short winter days, particularly working externally, there is a short window of opportunity to carry out such work and it is important that works are not started too late in the day, such that they cannot be satisfactorily completed during the working day/ available light. Cold, damp weather may also slow this process down, compounding the problem.

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Good Practice Guide

5. Foundations

The organisation, management and quality of foundations and substructures is arguably one of the most important work stages on any project.

All subsequent works rely on solid foundations; if we get this wrong, all else fails. This initial work activity is more significant than any other work stage for additional reasons.

It is the opportunity for us to ‘set out our stall’ and start as we mean to go on. Maintaining quality on a site that has set off on the right foot is much easier than trying to re-establish quality on a site without robust quality management control established from the outset.

Foundation and substructure works are also challenging to manage as they are typically bespoke in design, with different design solutions adopted depending on the building design and ground conditions present on any particular site.

Additionally, the type of ground conditions and seasonal weather conditions can severely impact working conditions, which may impact quality.

These should be considered when selecting the optimum design solution for a project as ‘buildability’ is an important aspect of quality. It is inappropriate to specify products that require ‘factory’ cleanliness in excavations in clay through winter months, as this may be impossible to achieve.

TRENCH / STRIP FOUNDATIONS Formation y Trench cut cleanly (appreciated that in these images they are formed in solid clay). y Vertical trench sides. y Clean and level trench bottom. y Clean and level shoulders and working area around the trench / oversite. y No loose material near top of trench that may fall into the excavation. y Trenches straight and setting out checked. y Trenches are free of standing water before concrete pouring. y Finished concrete levels confirmed.

Where applicable, ensure that stepped strip foundations are formed as noted in Approved Document A, Diagram 21.

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ELEVATION OF STEPPED FOUNDATION Foundations should unite at each change in level Minimum overlap L = twice height of step, or thickness of foundation or 300mm, whichever is greater.

S should not be greater than T (For trench fill foundations, minimum overlap L = twice height of step, or 1m, whichever is greater) Approved Document A, Diagram 21

Concreting y Stop ends, construction (day) joints and steps in levels established, where applicable, with formwork and setting out checked. y Reinforcement installed where designed, including at construction (day) joints to suit the engineer’s requirements. y Concrete finished with a smooth float finish. y Any concrete overspill removed from the surrounding oversite. y Temporary weather sheeting is to be applied when heavy rain is expected before the initial set. y Cold weather blankets are to be applied where required to protect from frost.

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Building Safety Act

5. Foundations Pile Preparation Piles are to be carefully cut down to the pile cap formation level, with close attention to ensure that the piles are not damaged. When cut, piles present a flat, level-bearing surface.

Piled Foundations A temporary piling mat is to be installed in layers and compacted as per the temporary works engineer’s design.

The pile is being carefully cut down, with debonding insulation over the reinforcement to the correct level.

Could this be better? Mushroom caps are missing and the excavation needs tidying.

Pile reinforcement y Cages are clean and free of contamination. y Cages are rigidly tied and contain the specified reinforcement bars and links. y Protective insulation is to be applied to permit correct reinforcement projection and lap.

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Piles have been carefully cut down to the required level. Temporary mushroom caps have been provided to the reinforcement. The formation level is clean and level.

Issues to avoid – Refer to the structural engineer in all such cases.

The pile-bearing head is damaged, preventing a transfer of load to the pile across its full cross-sectional area.

Reinforcement is not placed symmetrically within the pile and pilebearing face is damaged.

The pile head is damaged and not set out correctly relative to the ground beam. The engineer will need consulting where piles are outside the stated setting out deviation.

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Building Safety Act

5. Foundations

Ground Beams, Pile Caps and RC Ground-bearing slabs Ensure that the formation excavation is level and clean and that the piles project above the formation level in accordance with the engineer’s design with a clean flat-topped pile head.

Beams and pile caps should be designed with vertical sides to avoid unintended loads being transferred to the ground.

Where shutters are used, these must be straight and vertical.

Checks should include: y Reinforcement bars and mesh installed in accordance with design. y Minimum laps achieved (typically 40d – check with Engineer). y Cleanliness of reinforcement or flaky rust. y Cleanliness of blinding/formation and shutters – remove debris and standing water. y Reinforcement adequately tied to prevent deformation during the concreting operation. y Adequate cover is provided using robust spacers. y Provision of thermal blankets and/or heaters in cold weather.

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Anti-heave boards On many developments (generally containing expansive clay soils), compressible/void forming boards are installed to prevent ground heave damaging elements of the substructure. It is important that hard spots of grout or concrete are not created within these compressible or void-forming boards at board joints or where these boards are cut around pile heads etc. Joints and gaps must be sealed with suitable tape, expanding compressible foam, mastic or some other sealant. The method of sealing should be discussed and agreed with your engineer.

Joints between void-former boards sealed with tape.

Spacers / Concrete Cover Void former has been cut around the pile head, but not sealed against grout loss causing a hard spot around the pile.

Spacers are required to ensure that the minimum concrete cover to reinforcement is achieved. These can be made from concrete (max 50mm x 50mm) or proprietary plastic tack spacers (max 350mm length to avoid restricting the aggregate flow within the spacer profile). Spacer must be staggered to prevent the formation of a plane of weakness in the concrete.

Spacer layout

Spacers staggered to avoid planes of weakness Technical images source: nhbc-standards.co.uk

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Building Safety Act

6. Substructures

Every effort must be made to provide a good working environment for substructure operations, including clean level ground with safe access.

Substructure masonry This should be carefully set out and checked. Setting out errors at this point will impact all further works.

Bricks and blocks should be protected from inclement weather and stored on pallets up off the ground.

Substructure masonry should be constructed to the same standard as superstructure work, with consistent joints, fully filled and brick tie spaces at 900mm horizontally and 450mm vertically in a diamond pattern.

Mortar used below DPC must be as specified by the engineer. This may include sulphate resisting cement of other properties relevant to the prevailing ground conditions.

Where cavity walls are constructed below ground, these are to be concrete filled no higher than 225mm from DPC level.

The concrete fill should slope externally and be free from debris, mortar or rubbish.

Wall ties should be installed with a minimum of 50mm embedment.

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Cavity wall insulation must be certified for use below DPC. Where installed, this should be tight fitting, with no air gaps present. The insulation should be installed in accordance with the manufacturer’s instructions.

In this image, care has been taken to ensure that the installation is close fitting with neat masonry. Joints, including those to the cavity face, have been ironed and finished to ensure that these are fully filled.

A level working area and high-quality workmanship have resulted in excellent quality 'splash course' brickwork.

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Building Safety Act

6. Substructures

Care has been taken to align this airbrick neatly within the bond of the wall.

Air brick protection is a good way to keep airbricks clean and free from mortar and minor damage.

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Very neat substructure masonry has been achieved to this bay window.

An exemplary installation with the telescopic air vent installed correctly to the outer leaf of masonry. The cavity insulation will then maintain a warm envelope to the home.

The cavity is spotless.

The telescopic vent is located within an oversized hole (with lintel above) to enable the vent to align with the brick bond. This hole has been subsequently fully sealed up to prevent vermin and unwanted venting of the cavity.

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Building Safety Act

6. Substructures

Issues with telescopic vents In this image, all looks neat, but the telescopic vents have been incorrectly installed to the inner leaf of the wall, rather than the correct outer leaf. As installed, the cold air within the vents would cause a cold bridge within the home.

In this example, the telescopic vent was permitted to be filled with lean mix concrete. This will have to be fully cleaned before assembly, with all debris removed.

Here we see the careful installation of fibreglass insulation, including the correctly installed insulation to the warm/internal side of the telescopes.

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Insulation is tightly abutted, and wall ties are correctly installed at a maximum 900mm centred horizontally and a minimum 50mm embedment.

Neat and tidy substructure walls with lintels installed for services, drainage and air across flow.

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Building Safety Act

7. Drainage

Drainage should be: y straight with a minimum of 1:80 fall (12.5 mm per metre) or 1:40 where flow rates are less than 1L/second. y fully supported with a minimum of 100mm pea shingle. y rest bends supported by concrete.

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y temporary caps are inserted to prevent debris and contamination of the drainage system.

Please note that additional supports or joints may be required to suit ground conditions and movement.

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Where ground movement is anticipated an extended rest bend should be specified to ensure that the below-ground drainage and aboveground drainage do not part company or crush due to ground settlement or heave.

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Technical images source: nhbc-standards.co.uk

Where drains pass through substructure walls, one of the following two solutions must be adopted.

1.

2.

Pipes passing through a lintelled opening

150mm max.

150mm max.

600mm max.

600mm max.

Minimum 50mm space around pipe

Opening masked on both sides Flexible joint

Flexible joint

Pipe bedded in walls

Pipe passing through lintelled opening

Examples of where rockers have been correctly installed.

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Building Safety Act

7. Drainage

Drainage neatly installed with temporary caps fitted.

Vertical fill material should ideally be pea shingle however excavated material may be used providing it: y Contains stones no larger than 40mm. y Clay lumps no larger than 100mm. y No organic or frozen material.

Unacceptable, as it contains stones larger than 40mm

Unacceptable, as Clay lumps are larger than 100mm

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Another very important but often overlooked aspect of good below-ground drainage installation (and incoming water services), relates to the positioning of manhole/inspection chambers.

These must be set out correctly from the outset, mindful of the front entrance door location as well as hard and soft landscaping around the home.

Inspection covers have been positioned symmetrically across these terraces located within soft landscaped areas.

An example of where a lack of planning resulted in the inspection cover being positioned half across a ramp. This is unacceptable.

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Building Safety Act

8. Suspended ground floors

Beams should be laid on DPC and neatly aligned/cut to maintain a consistent cavity width at the party wall, with no steps or ledges.

Incoming services insulated a minimum 19mm wall thickness insulation at the time of service pipe installation.

Drainage setting out checked, hydraulically tested and capped.

The subfloor void should be clean of any debris, timber or organic matter.

Examples where beams/blocks are of incorrect length or badly installed creating insufficient bearing or projection into cavities, reducing cavity widths, insulation thickness or creating ledges and mortar build-up risks. This is unacceptable work.

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An example of neat, acceptable work.

An alternative insulated flooring system. This has been neatly jointed with the service duct carefully drilled.

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Building Safety Act

8. Suspended ground floors

Perimeter blocks have been neatly bedded on dpc.

Blocks have been neatly cut around service and drainage penetrations with blocks grouted as soon as possible.

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Insulation boards have been neatly laid over the beam and block with tightfitting joints and perimeter edges, neatly cut around drainage/service ducts and perimeter insulation to the screed area.

The incoming water service has been insulated throughout the suspended floor area with a minimum 19mm wall thickness insulation.

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Good Practice Guide

9. Superstructures

Another key element of any building is its structure and façade. It clearly plays a critical function in providing structural support for walls, floors and the roof, as well as a weathertight thermal envelope for the building.

More than any other element, it provides the building with its outward appearance and character. It is what homeowners, visitors and passers-by see, and pass judgement on our standards.

Superstructure elements (e.g. brickwork or render) need to be constructed right, first time and in a consistent manner, as inconsistencies or later remedial works are difficult, and in some cases practically impossible, to mask.

Good quality standards are also required to meet necessary energy efficiency standards and prevent dampness or weather penetration. With our climate continuing to suffer increasingly more extreme weather events, our new homes will need to keep warm (or cool in summer) and dry in all conditions.

Superstructures also provide a critical passive fire protection role. They are required to maintain structural fire performance for sufficient time to enable people to safely escape and provide safe access to fire and rescue services, as well as preventing the spread of smoke or fire.

External Walls Traditional Cavity Walls Things to look for: y Cavities are spotlessly clean y Lay boards are used to prevent mortar contaminating cavities or laying on insulation. y Coursing is maintained to ensure wall ties are level and definitely NOT back falling internally. y Correct wall ties are used to suit cavity width and location with minimum 50mm embedment each end (bedded and NOT pushed into joints). y Wall ties spaces at 900mm centres horizontally and 450mm vertically (both 2 block modules) in a diamond pattern.

On party walls – these must not be over provided as this may compromise the acoustic performance of the wall. y Additional ties to be installed within 225 of openings, gable pitch line and movement joints at every block course / max 300mm vertical centres. Wall ties installed within 450mm at horizontal openings.

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y Bricks and block bed and perpend joints should be fully filled and struck off / ironed in flush with the cavity wall face. y Cavity trays are required over all lintels, fire barriers, vents or other elements that close or bridge the cavity, as well as roof abutments where external walls transition to internal walls. Trays should be continuous, jointed and sealed with stop ends and clean of mortar. They should upstand a minimum of 150mm (typically 225mm / one block). y Care should be taken to ensure that cavity insulation is neatly cut in an angle to maintain the thermal envelope at cavity tray locations. y Weep vents are required to cavity trays (excluding rendered walls) at a minimum of 450mm centres (two bricks). A minimum of two are required per tray and should be installed consistently in relation to projection and horizonal alignment.

Working area clean and tidy to enable the bricklaying operatives to gain a safe and level access to work.

Cavity spotlessly clean, with wall ties clean and all joints filled and neatly finished.

Correct spacing of tiles to perimeter edges (within 250mm of vertical openings / roof pitch to gables at every block course and 450mm centres above and below openings).

Cavity closer installed using correct proprietary fixings into block bed joints and wall ties installed within 225mm of the opening.

Installing longer heavier ties to openings within wider cavities can be more difficult, but is possible.

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Good Practice Guide

9. Superstructures

Wall ties must installed within 225mm of a perimeter edge at every block course.

Boards should be used to keep cavities and insulation clean of mortar droppings.

Wall ties must be embedded 50mm in the bed joint as works progress – not pushed in afterwards.

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Lintels and steel beams must always be bedded on mortar. This ensures that the load is evenly distributed across the bearing face without any point loading, prevents weather ingress through capillary attraction and contributes to air tightness.

Work should be protected against rain, including cavity insulation. A DPC tray weighted down with bricks will keep cavities dry.

An example showing unacceptable practice where a lintel has not been bedded correctly.

All lintels should bear onto full, uncut masonry units (brick, block or blockette).

Here we see a temporary tray being laid onto the wall to provide temporary weather protection to the cavity.

An example of good practice where a clean cavity tray is turned up and stop ended into a perpend joint.

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Good Practice Guide

9. Superstructures

Care taken to neatly cut the insulation to the profile of the cavity tray.

Weep vents correctly installed directly on the lintel cavity tray with a consistent projection.

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Non-combustible weep vents to be used on >18m buildings.

Where deep reveals exist that exposes any part of the cavity in front of the window line, an additional tray is required under the cill of each window to catch and discharge any water that finds its way into the cavity via the cill / brickwork junction.

Vertical movement joints should, where possible, be masked by careful setting out of rainwater downpipes. Movement joints should never pass through window or door locations.

Slip ties should be installed to all movement joints.

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Good Practice Guide

9. Superstructures Roof line Waterline

R

af

te

r

Cavity tray installed towards the top of the bed joint

Cut bricks introduced to ensure heel of trays installed against ‘waterline’

Min 65mm

y Proprietary stepped cavity trays must be installed wherever pitched roofs abut external walls (site formed dpc trays are not accepted by NHBC). y They must be installed with their ‘heel’ in alignment with the waterline as noted below. A profile is required in every case to ensure that the waterline is correctly set out. A double stop-ended catchment tray with weep vent is required at the bottom of the tray cascade.

Joints raked out below cavity tray by 25mm whilst mortar green

y Bed joints at the tray locations should be raked out whilst green to allow for the subsequent recessed flashing.

Here the site team has ensured that a truss has been positioned ahead of the scaffold, enabling the precise waterline and subsequent stepped trays to be correctly installed.

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Joints raked out at stepped cavity tray locations ahead of this hipped bay roof.

A finished hipped roof bay with weep holes evident in the bottom catchment tray.

Vertical trays correctly installed to the sides of this flat roofed bay.

Tray and weep vents correctly installed to this parapet / external wall abutment.

Here is an example where the setting out of the tray is incorrect. The heel of the catchment tray does not coincide with the waterline.

Tray and weep vents correctly installed to this mono pitch low level roof abutment at a minimum of 75mm above the pitched roof / wall intersection.

Correctly located tray and weep vents to this recessed electrical meter box (one course above the opening to accommodate the meter box flange).

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Good Practice Guide

9. Superstructures

Neat work even under a challenging lighting condition, confirming a significant flatness and consistency of finish to these walls.

Straight bed joints.

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Impressive that this wall has been laid and finished with pride even when it is to be plastered.

Care taken to consider how to accommodate a flue through this brick detail (the same would apply for a ventilation grille).

Plumb perpend joints indicating a consistent bond.

A similar detail where no thought was given.

Neat work to complex details.

On the face of it, this party wall looks neatly constructed. On closer inspection the wall ties have been installed at 450mm centres horizontally (not 900mm). This creates a more rigid wall that provides an increased sound path across the wall and is therefore not acceptable.

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Good Practice Guide

9. Superstructures

Framed Buildings

Joist ends neatly filled with blockwork (Note – that NHBC Standards 2024 now require these joist ends to be mastic sealed so that air tightness is maintained during timber shrinkage or movement.)

Light gauge steel infill panels are installed with deflection heads to permit structural deflection.

‘Toothing’ of brickwork is not permitted as it often leads to unfilled bed joints. Where work cannot progress to an opening, it must be raked back and not toothed.

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Sheathing board to the light gauge steel frame is sealed to all perimeters using Class B EPDM.

Preformed corners used on all cavity trays (non-combustible type required to buildings >18m). Site formed corners are not to be used, preformed flexible corners are now available and acceptable.

Cavity barriers are required to all party floor and wall locations. Here, exceptional care has been taken to neatly cut the fire barrier tightly around this dog toothed brickwork design.

Windows and duct penetrations are sealed against the sheathing board using Class B EPDM.

Care has been taken to carefully cut the fire barrier around this masonry support angle.

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Good Practice Guide

9. Superstructures

Vertical cavity closers and barriers are tight fitting.

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Full bricks or rotated cut bricks are used to ensure a full-face contact with the cavity barrier.

A clean and tidy working platform with pockets formed and temporary hessian laid on the cavity trays (removed via the pocket) to present a clean mortar-free cavity tray on completion.

Spotlessly clean cavities and wall ties with all bed and perpend joints fully filled.

An example of some complex and neatlyfinished face brickwork.

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Good Practice Guide

9. Superstructures

Examples of well-blended consistent brickwork with straight vertical movement joints of consistent width.

Care taken to install this intumescent open state horizontal fire barrier at the compartment floor location behind a rainscreen cladding system.

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Internal Masonry Walls

This internal blockwork will ultimately be covered with plaster and wall finishes; however pride has been taken to present the blockwork to a very high standard, with all joints fully filled and jointed.

Neat work, coursed correctly to provide the lintel bearing onto a full masonry unit.

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Good Practice Guide

9. Superstructures

Timber Upper Floors

Adhesive should be visible from below.

A 10mm minimum clearance gap is maintained between the floor decking and the walls.

Lateral bracing should be installed in accordance with the floor manufacturer’s design, the timber should be fixed tight to the external wall to provide lateral support with a suitable metal strap taken into the cavity and tightly abutting the inner wall leaf.

The stairwell is temporarily decked over to provide a safe working platform.

Decking boards are staggered and fully glued to all joints and to the joists below. These are then screwed whilst the glue is wet and screw heads sealed with adhesive.

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Face brickwork protected from cold weather using hessian sheets.

Reinformed concrete structures are not included within this guidance document, however one issue that required careful consideration is the location of service riser openings incorporating GRP grillage. It is important that the face of the concrete opening does not recess below any part of any plasterboard fire-rated wall, as this will compromise the performance of the wall if the sole plate is not fully protected by all layers of plasterboard within the wall build up.

In this image, the fire partition overhangs the riser opening and the metal has no protection from the effects of fire. This is not an acceptable construction.

An example of service riser openings with cast in GRP safety grillage.

Pre-cast concrete plank floors – considerations y Ensure that the concrete planks align with the inner face of the cavity wall to prevent bridging of the cavity, (including reduced thermal insulation thickness where this may occur). y Where the pre-cast planks coincide with cavity fire barriers, the voids should be filled to maintain a solid floor width contact with the barrier material. y Care should be taken to ensure that suitable bearing is provided to the PCC planks, particularly where these include three-sided service openings. If in doubt, refer any concerns to the structural engineer. y Consideration should be given to PCC camber and its potential impact on screed thicknesses or the initial coursing / bedding of masonry walls that occur mid span.

In this image the PCC planks should have their hollow cores filled to provide a full abutment face for the fire barrier.

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Good Practice Guide

10. Roofs

Roofs perform a critical function in keeping a building watertight. The primary requirement of any roof structure is to keep the rain out of the building. Year on year, new home warranty providers report the single highest area of claim relates to roof failures; any weakness in relation to quality will almost certainly result in a roof failure.

The roof may also provide structural support to the walls and floors of the building and prevents the passage of smoke or flame between buildings or through fire compartments. Subject to the height of the building and specific detailing, the construction of the roof, including insulation material, may be subject to restrictions on fire performance to prevent external fire spread.

Terminology: y Rafter: carries the weight of the roof finish (e.g. tiles) and provides fixing for underlay and battens. y Ceiling joist or tie: triangulates the rafters, stopping the walls and roof spreading outwards. Also supports the loft insulation and ceiling boards and loft access boards and platforms. y Ridge: provides fixing and spacing for the tops of the rafters or trusses. y Purlin: supports long span rafters to prevent deflection and increase stiffness. These are typically timber or structural steel.

Pitched Roofs (a roof angle between 10° – 70°)

y Struts: give support to purlins to prevent deflection and transmit roof loading to the structure below.

Structure

y Collar: ties the roof together at purlin level.

Concrete roof tiles weigh approximately 46kg/m2, so the overall weight of a fully-tiled roof can be many tens of tonnes or even hundreds of tonnes on large roofs. It is crucial, therefore, that the roof structure is sound to safely transfer this load through the loadbearing structure of the building.

y Ceiling binders and hangers: supports long span ceiling joists. y Pole plates: similar to purlins but used where ceiling joists are above wall plate level.

There are two types of pitched roof: a traditional cut roof, using structural grade timber cut and constructed on site by a carpenter or a truss rafter roof, using factory manufactured truss rafters (or a combination of both types). All roof structures must be designed by a structural engineer.

Ridge

Purlin Hanger Binder

Collar Strut

Wall plate

Load-bearing wall

Technical images source: nhbc-standards.co.uk

48

Pole plate spanning between load-bearing walls

Technical images source: nhbc-standards.co.uk

d

d

Where rafters are birdsmouthed over wall plates, these must never be cut more than 1/3 the overall depth (d) of the rafter member.

In this example of poor workmanship, the carpenter has used a circular saw and overcut the joint. If circular saws are used to cut the birdsmouth, this should be completed using a hand saw.

The most common type of roof in new domestic buildings is trussed rafter roof. These are of a lighter weight construction that a traditional cut roof as they gain their strength on being a triangulated frame with strong truss plate connectors.

Being of smaller section size, care must be taken when storing and transporting them to prevent damage.

Roof trusses stored off the ground on a scaffold truss rack.

Continuous binder Incorrect truss storage

49

Good Practice Guide

10. Roofs

The maximum distance a trussed rafter can project over a wall plate is as noted below:

Rafter

S

Continuous binder Ceiling tie

Trussed roofs incorporating valleys are typically formed from diminishing trusses.

Diminishing trusses should be supported on splayed bearers or a proprietary truss support bracket.

Max. projection= whichever is larger

Wall plates are required to secure and evenly spread load from rafters or trusses onto the walls.

They should be:

Steel tie prevents spread of hip rafter y Bedded to a line and level using nails or straps Plywood angle to hold them down. tie prevents wall plates y Not less than 3m length (generally) and should spreading extend over a minimum of 3 joists / rafters or trusses. y Jointed using half-lap joints at corners and running lengths.

derneath the 25x100mm ongitudinal bracing (or an nal timber member) fixed minimum of eight screws

Bracing fitted tightly to internal face of block inner leaf

y Where specified, have holding down straps a minimum of 1m long with a cross section of 30mm x 2.5mm fixed at a maximum of 2m centres. y Where into masonry, a minimum of four number, 50mm long no. 12 wood screws (into suitable plugs). y Provided so that the lowest fixing is within Timber angle 150mm from the bottom of the strap.

Technical images source: nhbc-standards.co.uk

50

tie prevents wall plates spreading Dragon tie prevents spread of hip rafter

Technical images source: nhbc-standards.co.uk

In these images, the wall plate is correctly bedded Rafter with a on mortar (circa 10mm bed thickness) cross-halving joint where wall plates are joined.

S

whichever is larger

d

Ceiling tie

Ceiling tie

Max. projection=

d

S

d

d

Rafter

Max. projection= whichever is larger

In this first image above, an additional timber has been fixed to the wall plate to provide a secure fixing for the diagonal roof bracing.

Continuous binder

Continuous binder

Triangulation: Angle ties should be used on hipped-roof corners to prevent the wall plates spreading. For heavily-loaded hip rafters, dragon ties or similar bracing should be used to prevent hip rafter spread.

Timber angle tie prevents wall plates spreading Dragon tie prevents spread of hip rafter

Timber angle tie prevents wall plates spreading Dragon tie prevents spread of hip rafter

Steel tie prevents spread of hip rafter Plywood angle tie prevents wall plates spreading

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Good Practice Guide

Continuous binder

10. Roofs

Continuous binder

Lateral restraint straps must be installed to all gables. y For homes up to and including 3 storeys – 2m centres Timber angle y For homes above 3 storeys – 1.25m centres.tie prevents wall plates spreading They must be fixed one of two ways (as follows) and fitted tight to the inner leaf Dragon tie of the cavity wall and turned down across a substantial piece of masonry. prevents spread of hip rafter

Timber angle tie prevents 1. Fixing to solid noggings using a minimum wall plates of four 50mm x 4mm steel screws or four spreading 75mm x 4mm (8SWG) round nails, withDragon one tie prevents fixing in the third rafter (Figure 15) spread of hip rafter Strap underneath solid noggings, fixed with a minimum of four fixings (at least one in the third rafter)

Strap underneath solid noggings, fixed with a minimum of four fixings (at least one in the third rafter)

Block removed for clarity Packing between rafter and wall Strap held tightly against block inner leaf

Block removed for clarity Packingtobetween Nogging fixed horizontally avoid twisting the restraintrafter strapand wall Strap held tightly against block inner leaf

Nogging fixed horizontally to avoid twisting the restraint strap

Technical images source: nhbc-standards.co.uk

52

2. Fixing to longitudinal bracing members using eight 25mm x 4mm steel screws evenly distributed along the length of the strap (Figure 16).

Alternatively, 100mm x 25mm timber members, fixed over the four trusses and Strap underneath 25x100mm longitudinal with bracing (or an7.2.9 nailed in accordance Clause additional timber member) fixed can bewith used where the position of a minimum of eight screws the strap does not coincide with a longitudinal binder.

Strap underneath the 25x100mm longitudinal bracing (or an additional timber member) fixed with a minimum of eight screws

Steel preve sprea hip ra Plywo tie pr wall p Bracing fitted tightly to internal sprea face of block inner leaf

Bracing fitted tightly to internal face of block inner leaf

Strap held tightly against block inner leaf

Strap held tightly against block inner leaf

Here are some examples of poor quality.

This strap is not in contact with the block wall and therefore offers no lateral support.

Very good practice has been adopted here.

A gauge rod is used to accurately set out the location of the straps, ensuring that it sits within the block bed joint and laps over substantial block.

A good example of fixing straps using the ‘noggin’ method.

In this image, the strap is buried within this large section of mortar. The mortar is liable to crack, and the strap will offer limited or zero restraint to the gable wall.

The strap must be in full contact with a substantial block element. In this example, it has been set out perfectly to suit block coursing.

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Good Practice Guide

10. Roofs

Bracing required for trussed rafter roofs. y All bracing to roofs should be a minimum of 100mm x 25mm timber (3mm tolerance applies).

Binders abutted tightly against gable and separating walls

y Nailed twice to each rafter it crosses; fixings should be 3.35mm x 65mm (10 gauge) galvanized round wire nails or minimum 3.1mm x 75mm mechanically-driven gun nails. y Where braces and binders are not continuous, they should be lap-jointed and nailed to a minimum of two trusses.

Diagonal bracing: y Diagonal and longitudinal bracing should be provided at rafter level. y Diagonal and chevron bracing should pass across each rafter in the roof, however, small gaps, such as two trussed rafters between sets of bracing, or one trussed rafter adjacent to gable or separating walls, is permitted in the middle of an otherwise fully-braced roof.

y There should be a minimum of four diagonal rafter braces in each roof; in narrow-fronted roofs and mono-pitched roofs, where the braces cross, the intersection detail should be used as noted in NHBC Standards Chapter 7.2. y The diagonal bracing should extend over and be directly fixed to the wall plate, fixings should be 3.35mm x 65mm (10 gauge) galvanized round wire nails or minimum 3.1mm x 75mm mechanically-driven gun nails.

Longitudinal bracing members should extend the full length of the roof, tightly abut gable and party walls and permit diagonal bracing to pass (they may be lapjointed providing the overlap is nailed to a minimum of two trussed rafters).

Technical images source: nhbc-standards.co.uk

54

Binders fixed to ceiling ties of trussed rafters, where necessary using two lap-jointed lengths

Binders abutted tightly against gable and separating walls

Binders fixed to ceiling ties of trussed rafters, where necessary using two lap-jointed lengths

Restraint straps fixed to timber spanning 4 rafters. Lateral and diagonal bracing fully installed and correctly lapped over a minimum of two trusses.

Longitudinal bracing installed tight to the gable wall. Restraint straps installed to the ceiling joists and diagonal bracing secure up to the gable wall.

Vally boards are carefully cut and installed to fully support the GRP valley tray.

Diagonal bracing securely fixed to the wall plate and neatly trimmed.

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Good Practice Guide

10. Roofs

Pitched roof coverings Things to look for: y The roof underlay, tiles, gauge and method of fixing are all specified in a manufacturer’s fixing schedule taking into consideration the location and design of the roof in question. y Roof underlays must be suitably lapped (and sealed where specified by the roof system manufacturer) at batten locations. These must be undamaged and neatly cut around penetrations using the ‘inverted T’ method or in accordance with instructions for proprietary roof terminals. y A suitable pre-formed eaves tray and UV resistant underlay is required over fascias at eaves locations. y Fascia heights should be carefully coordinated between the roofer and carpenter as this height is determined by the pitch of the roof and type of roof covering applied. Fascia boards fixed at the incorrect height will cause the roof to drop or rise up at the eaves, causing potential for water ingress through open lap joints (dropped tiles) or insufficient lap length on shallow pitch areas (raised tiles). y Roof battens should be of a BS:5534 structural grade timber with staggered joints, spanning a min of 4 rafters (where possible). y Cut battens should be treated with a siteapplied timber preservative, in a contrasting colour to that of the batten. y The space between the battens should be fire sealed using stone wool wherever roofs cross compartment walls.

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y Verges to gables should be formed using proprietary verge systems or wet bedded onto 100mm of roofing mortar. y All tiles should be twice fixed plus any additional tile clips specified by the roof manufacturer. y Abutments with plain tiles require code 3 lead soakers (double-lapped tiles) or proprietary abutment gutter trays. Code 4 lead flashing is required to dress over this. y All leadwork (flashings, trays, valleys, saddles etc) must be treated immediately on completion of the work, with patination oil. Leadwork should be installed in accordance with the Lead Sheet Association publication: Rolled Lead Sheet, The Complete Manual. y Where rolled, single-lapped tiles are used, providing the flashing discharges into the ‘trough’ of the tile, a gutter is not required. y Ridge and hip tiles to the main roof must be mechanically fixed. End tiles must be twice fixed to prevent uplift, and where required to be cut, should be spread over a number of tiles to avoid small cuts at the exposed roof ends. y Roofs should be gauged to ensure that the minimum head lap specified by the manufacturer for the location and pitch of roof is maintained and discharge over the centre line of the eaves gutter. y Roof vents should be set out to offer the shortest possible run within the loft area and, where possible, discharge to the rear facing elevation.

Batten spacing Headlap

Technical images source: nhbc-standards.co.uk Gauge

Headlap

Single or double-lapped tiles?

Batten spacing = Gauge

Batten spacing Double-lapped tiles, rely on a combination of three overlapping tiles to create a watertight roof. They are typically available in 1/2, full and 1 1/2 tile sizes and can be cut, making them Gauge very suitable for complex roofs.

The headlap is measured across alternate tiles where they are double lapped as seen below:

Double-lapped tile terminology Tile battens

Headlap

Top course tiles

Gauge

Gauge

Headlap

Eaves course tiles

Tile battens

Top course tiles

Sidelap

Single-lapped tiles are well suited to large simple roofs.

They cannot be cut except at perimeters and are generally unavailable in modules other than full tiles. WhereGauge small tiles are unavoidable, they must be bonded to a larger tile using an adhesive approved by the tile manufacturer.

Typical eaves tile clip

Headlap

Single-lapped tiles rely on a watertight interlock detail to keep them weathertight. Care must be taken that these are Eaves course tiles not damaged.

The headlap dimension on single-lapped tiles is measured to the tile immediately below as shown here.

Typical tile to tile clip

Sidelap

Headlap

Gauge

Typical general tile clip

Batten spacing = Gauge Batten spacing

Additional fixings may be specified by the roofing manufacturer in its fixing schedule and these must be installed where required.

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Good Practice Guide

10. Roofs

Roof underlays Care should be taken not to stretch roof underlays tightly. They should have a 10mm natural sag to transfer any collected water into the gutter and not to the batten-fixing positions. The underlay must not have a sag greater than 10mm or the ‘billowing effect’ may lift the tiles off the roof.

When too tight, water runs to nail holes Slight Sag

Roof battening In this photograph, roof battens cut correctly so that they do not all fall on the same rafter. y Batten spacing > 200mm, no more than one batten in any group of four should be joined over any one truss or rafter. y Batten spacing ≤ 200mm, no more than three joints should be made over any twelve consecutive battens.

The underfelt, however, is stretched too tightly with no sag between the rafters and the joints in the underlay have not lapped under a batten.

Cut ends of roof battens can clearly be seen to have been treated with a brush-applied timber preservative.

58

Leadwork Lead is commonly used in roof flashing and detailing and is generally used on roofing in three standard weights.

Code 3 – soakers Code 4 - cover flashings Code 5 – valleys, formers etc.

All lead work should be installed in accordance with the Rolled Lead Sheet: ‘the complete manual’ as published by the Lead Sheet Association.

Dry or wet work Subject to the specifications of any given project, details such as valleys, hips, ridges or verges may be formed from dry fix proprietary products or using traditional wetbedded mortar.

Where proprietary systems are used, the works must be installed fully in accordance with the manufacturer’s instructions – a copy of which should be made available by the roofing contractor.

A well-constructed dormer with skilled code 5 leadwork applied. It must be noted that as these are single-lapped tiles, a wall interface gutter is required under the lead cover flashing where the roof abuts the cheeks of the dormer.

Where wet work is specified, mortar must only be as noted below: Bricklayers mortar or silo mix must NEVER be used on roofs. The soft sand contained within these mortars lacks the tensile strength required, even if additional cement is added.

Roof mortar must be a minimum of 1:3 cement to sand and the sand must contain a minimum of 1/3 sharp sand, plus suitable mortar plasticiser. Alternatively use proprietary mortars specifically designed for roof work.

1:3 + Mortar Plasticiser

or Minimum 1/3 Sharp Sand

+

+

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Good Practice Guide

10. Roofs Setting the correct height of the eaves fascia requires consultation and collaboration between the carpenter and rooking contractor, as one size definitely doesn’t fit all.

FASCIA HEIGHTS

Double lap tiles

Single lap tiles Natural slate

The correct fascia height ensures that the tiles do not drop or kick up at the eaves location. The height is determined both by the pitch of the roof and also the type of roof covering, with double-lapped tiles typically requiring a higher fascia height to a natural slate, and with a single-lapped tile requiring a fascia height between the two.

Allowance should also be made for any eaves ventilators that may be fixed to the fascia to provide ventilation to the roof.

Fascia

Height is inclusive of any fixed eaves vents.

In this photograph, the fascia has been positioned too low, resulting in the last course of tiles dropping and opening up a wide joint that wind and rain may penetrate.

Proprietary UV-resistant eaves boards are now widely used in lieu of tilting fillets, and these should be positioned under the roofing underlay, and discharge into the centre of the gutter.

They prevent potential ponding of water on the underlay behind the fascia.

The finished roof covering should be gauged (and hip tiles cut) so that they finish over the centre line of the gutter.

Here is an example of a roof where an eaves tray has not been installed and ponding has occurred. It is only a matter of time before this ponded water gets into the roof.

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Setting out a roof It is important that the roof is correctly set out prior to commencement to ensure that minimum headlap / tile gauge and side laps are achieved, as well as correct overhangs to gutters and verges.

This operation is particularly important when using single-lapped interlocking concrete tiles, as the availability of tiles other than full, standard tiles is very limited. With single-lapped interlocking tiles good practise dictates that vulnerable, cut tiles should always be positioned on the right-hand verge, as this gains the added support of its neighbouring tile that laps over and holds it down, whereas the left-hand verge tiles sit on top of their neighbouring tile.

As interlocking tiles are laid right to left, it is important that this basic setting out is carried out prior to commencement.

Concrete interlocking tiles have something called ‘shunt’ allowing them to be closed-up or opened slightly to assist in eliminating small cuts. Again, this should be checked and set out prior to fixing any tiles.

3mm - 4mm shunt per tile (refer tile manufacturer)

Interlocking tiles are laid right to left. If roof not set out before tiles laid, the weak cut tile will be on the left

2nd Option

1st Option (protected by adjacent tile)

If shunting cannot achieve full tiles achieve minimum ½ tile + at verge

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Good Practice Guide

10. Roofs Roof Tile Setting Out Plain double lapped tiles and slates Full tile

1½ tile

Cut tile

Double-lapped tiles and slates are substantially more flexible, as in addition to standard sizes, they are available in 1 ½ tile modules.

They also do not rely on interlocks and so can be cut where required (making sure that minimum side laps are maintained).

Verges Verge clips MUST be in twice fixed to battens and be in full contact with the roof tile (if not the clip is not fulfilling its function to hold tiles down. In the case of profiled tiles, differingsized clips may be required to achieve this, depending on where the cut occurs.

100mm mortar bed

A cut tile being inserted into a double-lapped roof.

Underlay taken over wall cavity

Verge tiles bedded in mortar on undercloak

Batten finished with a contrasting preservative where cut

Verge overhang 38-50mm (double lapped slates / tiles) & 30 – 60mm (large interlocking tiles)

Rafter / truss to wall alignment is important to ensure tile batten holds down the undercloak.

Undercloak should be bedded on mortar.

External wall should be 10mm lower to allow bedding.

Technical images source: nhbc-standards.co.uk

Where verges are wet bedded, the tiles must be bedded onto a firm 100mm mortar bed to provide full adhesion and compaction. It must never be pointed-in after tile laying.

Slates do not require mortar bedding.

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Neat, well-constructed wet verges with verge clips, all in contact with the tiles and the bedding mortar neatly pointed up.

Where wet-bedded verges are specified, these must be neatly shadow pointed as indicated below and not flush pointed.

These are the wrong verge clips - they should be in contact with the tile holding it down. This image also indicates that the roof wasn’t set out prior to tiling, as the cut tiles should be on the right-hand verge, not the weaker left hand verge.

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Good Practice Guide

10. Roofs

Valleys These days almost all valleys are constructed using a dry GRP valley former. Please refer to the valley manufacturer’s standard instructions for their installation. This should typically include a suitable timber valley former support under the tray. Fascia boards should be notched to avoid the valley tray distorting as it runs to the gutter line. Alternatively, a lead saddle can be provided at the eaves location.

Running ridge tiles over valleys is bad practise as this creates a large mortar bed liable to crack, and often conceals the lack of adequate saddle flashing over the valley.

A more robust solution that should be followed maintains an open valley across the line of the ridge as detailed here.

lead saddle flashing dressed over GRP valley gutter

GRP valley gutter

Technical images source: nhbc-standards.co.uk

64

Double lapped valley tiles

Cut tile

Small cut tiles When cutting valley tiles, please avoid very small cuts. For doublelapped tiles or slates, use 1 ½ tiles and for single-lapped interlocking tiles, bond tiles together using a manufacturer’s approved adhesive.

Valley tiles must NEVER be cut in situ. They must be marked and wet cut away from the roof to avoid potential damage to the valley liner and respiratory concerns caused by dust inhalation.

Cut tile to a weak point

Valley tile now wider at the tail (stronger)

Incorrect use of small cuts

Tile and a half used to avoid small cuts or to extend tiles further into the valley

Often, small cut tiles are unavoidable within roofs, especially where features such as roof lights, dormers or PV panels exist.

In this situation, where single-lapped tiles are used, the only solution is to carefully bond the cut tile to the adjacent tile using a manufacturer’s approved adhesive.

While double-lapped tiles or slates are generally available in 1 ½ tile modules, overcoming the need for small cut tiles, single-lapped interlocking tiles are typically designed to fill large, uncomplicated roof areas and are generally not available in larger sizes.

All tiles should be twice mechanically fixed and where small cut tiles are unavoidable, these should be bonded to a larger tile using a suitable cartridge-applied adhesive, approved by the tile manufacturer.

Cavity tray Min. 75mm

Lead flashing wedged into joint below wall DPC

Where pitched roofs abut walls, a cavity tray must be installed with a joint raked out whilsteach Soakers beneath tile and overlapped green to receive a code 4 flashing dressed by the flashing under the tray. A minimum of one brick (75mm) upstand is required from the finished roof and a minimum 150mm downstand.

Step held with

Min. 150mm Clip free edge of flashing; method depends on exposure

Underlay turned up behind flashing

U up Technical images source: nhbc-standards.co.uk

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Good Practice Guide

10. Roofs Where double-lapped tiles or slates abut a wall, this can be formed using code 3 lead soakers with cover flashings or proprietary roof abutment gutters.

Soakers beneath each tile and overlapped by the flashing

y

Stepped lead flashing held in mortar joints with lead wedges

Lead flashing wedged into joint below wall DPC

Soakers beneath ea tile and overlapped by the flashing

Min. 150mm Clip free edge of flashing; method depends on exposure

Cavity tray

Lead flashing wedged into joint below wall DPC

Min. 75mm

Min. 150mm Clip free edge of flashing; method depends on exposure

Cover flashings only acceptable on plain tiles where turned soakers (or Secret gutters) used.

Underlay up behind flashing

Underlay turned up at abutment

Underlay turned

A nicely detailed hipped bay roof using double-lapped clay tiles and up behind flashing baby hip tiles. These are fully wet bedded with hip iron supports (hips to bay windows do not require mechanical fixing), however this should be actioned by carefully drilling through the crown of the tile and fixing with a stainless-steel screw and rubber washer. The roofer has also taken care to introduce a cut hip tile within the body of the run of tiles and not at the more exposed and visually obvious end tiles.

Code 3 lead soakers and a code 4 lead cover flashing neatly finished the abutment to the wall – all tucked under the horizontal tray and proprietary stepped cavity tray.

Profiled tiles can simply be dressed with a suitable flashing that must terminate into the trough of the tile, or a proprietary abutment gutter can be used.

Where the tiles are flat, or a profiled tile is cut, removing the trough, a proprietary abutment gutter MUST be used. NHBC no longer accept proprietary plastic slide-on soakers.

7.2

Where single-lapped concrete interlocking tiles are used, soakers are not applicable. Abutment solutions depend on whether the tiles are profiled or flat.

Only acceptable into a rolled / profiled tile

An example of a proprietary roof abutment gutter Technical images source: nhbc-standards.co.uk

66

Fire barriers A stone-wool fire barrier being installed over a fire wall compartment line between each tile batten (Note: the Hill policy is now to use wired tile batten barrier, such as that provided by ARC)

Here you can see the compressible stone-wool fire barrier to the top of a spandrel panel, maintaining the fore compartment through the roof covering. (Note: the Hill policy is now to use the ARC spandrel barrier).

An excellent example of very well-cut mitres to the hip and ridge intersection preventing the commonly seen ‘big top’ effect, where the ridge tiles rise due to incorrect mitres being formed. Also, very neat mechanical fixing including the introduction of an additional fixing to the ridge and hip ends to ensure they are twice fixed, to prevent wind uplift.

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Good Practice Guide

10. Roofs

Photo-voltaic panel installations There are two basic forms of solar panel installation to pitched roofs.

1. On roof A framing system is fixed through the roof covering and the panels are mounted on top of the roof covering. Fixing details must not compromise the weather resistance of the roof covering or lift tiles from their natural lay.

2. In roof The PV is an integral part of the roof and its installation must be flashed and sealed to maintain the roof’s weather resistance. Due to the impervious nature of ‘in roof’ PV panels, additional roof vventilation may be required where this solution is adopted.

In all cases: y Waterproofing details that rely solely on sealant are not acceptable. y Bolt through fixings are NOT suitable for double-lapped tile or slate situations. They must pass under the tiles. y Bolt through fixings to single lapped tiles must not penetrate interlocks or be located less than the minimum side lap dimension for the tile/pitch. y Tiles must lay flat and not be stressed by any PV fixings.

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Flat roofs Flat roofing systems are typically bespoke and should therefore be designed as a complete system in accordance with NHBC Standards Chapter 7.1 or section 11 and 12 of the LABC Technical Manual.

Consideration should be given to the specified surface and functional specification of the roof system (i.e. green, brown, blue systems, podium, terrace, vehicular access etc.) and ensure that the roofing system is designed accordingly, taking into account:

y Dead and live loads (e.g. trees, vehicles etc.)

y Simplicity and skill level required to install

y Weight of the roofing system

y Sensitivity to failure (e.g. single ply membranes vs bonded systems)

y Wind uplift y Functional performance y Surface finish y Buildability / compatibility with programme and sequencing requirements y Robustness against physical damage during construction or in use

y Impact of inclement weather during construction / cleanliness requirements

y Fire – Refer to Hill Technical Policies, job specific fire strategy documents and current legislation depending on the location of the roof and type of building y Potential hot work fire and CDM risks y Movement

y The type of substrate and system compatibility

y Complexity of junctions and interfaces

y Falls / drainage requirements

y Thermal performance requirements

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Good Practice Guide

10. Roofs

Flat roofs need to have facilities to manage rainwater in the eventuality of blocked outlets or drainage. Typically, these require overflow arrangements or multiple outlets with independent drainage systems.

In this image a cold spray applied system has provided a waterproof seal to the overflow pipe.

In this photo, the BRoof (t4) roof membrane is bonded to the parapet wall of this building up to a height of 150mm above the roof finish level. Membranes above this roof interface must be a minimum fire classification of B-s3,d0 to meet Hill’s and Approved Document B guidance.

Flat roofs, terraces and balconies should include a 150mm upstand to perimeters to provide splash protection to the abutting wall.

A suitable cavity tray should be installed to coincide with the top of the waterproof upstand. The tray should discharge over the waterproof upstand.

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Parapet abutment to cavity wall

Alternative abutment using metal coping with integral stop end

Here, the flat roofing system has been incorporated within the parapet capping detail and links to the cavity tray.

All parapet walls require a well-installed DPC designed to resist the downward movement of water i.e. they must be continuous of fully lapped and sealed where jointed, as shown in this image.

Very neat cutting and laying of paving has resulted in a first-class finish to this balcony, including a consistent margin to the perimeter edges.

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Good Practice Guide

11. First fix (carpentry, M&E services, drylining, fire stopping and windows) Carpentry Stairs Key design and construction considerations: y Stairs should meet the requirements of the building regulations. y Have a minimum headroom ‘H’ of 2m as noted in the diagram below.

H landing

Where timber stairs sit on a wet screeded floor, a suitable DPM must be provided to protect the staircase from residual moisture Diagram 1 - wash basin contained within the screed until fully dried.

H

300mm min.

300mm min.

pitch line

Squeaking and creaking stairs are a common defect within WB the industry, and we must do all we can to prevent this Electrical accessory ELEVATION occurring in a Hill home. Care must be taken whenswitch fixing e.g. socket, consumer unit etc. timber stairs as follows: 1. Keep stairs indoors and protected against excessive moisture (do not lay directly on screeded floors).

timber framing

2. Ensure that all treads and risers are solidly glued and wedged into the stair strings.

Diagram 2 - sink

line the enclosure and 300mm min. min.

3. Ensure that stair strings are secured300mm to adjacent walls wrap the pipe with 25mm unfaced mineral wool with screws at 300mm centres, with solid blocking behind. (min. density of 10kg/m3)

4. Treads and risers should be solidly glued and jointed to

the material of the enclosure the strings. should have a mass of 15kg/m2

This installation is not acceptable as the DPM was omitted.

vertically or horizontally to switch or outlet

300mm min.

ELEVATION 300mm min.

5. Once installed, there should be no detectable movement within the stairs when in use. If there is movement, please address the adequacy of the fixings or consult with the stair manufacturer, as over time this will lead to creaks and worktop sink squeaks along with cracking of finishes. drainer

in shaded zone 150mm wide

PLAN

Fire – in many situations, the stair enclosure acts as a protected escape route. Where the underside of the stair structure is exposed to a fire risk (e.g. storage cupboard) or a space outside the protected enclosure, a suitable structure will be required to provide the necessary fire resistance. Typically, this will involve lining the underside / exposed stair structure with a fire protective plasterboard or fireline board.

Technical images source: nhbc-standards.co.uk

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Diagram 3 - Hob 100mm min.

100mm min.

Technical images source: nhbc-standards.co.uk

H landing

Soil and vent pipes (SVPs) within dwellings should H be boxed and wrapped in a minimum of 25mm of unfaced insulation. The boxing should be double boarded to achieve a minimum density of 15kg/ pitch line m2. This is required to provide sound insulation and is therefore not needed to sections of SVP that act purely as vents.

Where offsets occur, Hill requires the insulation to be double layered to 50mm.

timber framing line the enclosure and wrap the pipe with 25mm unfaced mineral wool (min. density of 10kg/m3)

In this photograph, the stair string is securely fixed to the adjacent wall at a maximum of 300mm centres through solid packing. To provide additional strength and to ensure a robust fire seal, fire foam has been sprayed between the stair string and the wall.

the material of the enclosure should have a mass of 15kg/m2

vertically or horizontally to switch or outlet

in shaded zone 150mm wide

Window boards should be secured with strapping and expanding foam sealed as noted below. For buildings >11m in height, the foam must be a fire-rated product, minimum class A2–s1, d0.

Where specified, the window boards should have consistent returns to each side of all windows within the home. The profile of the return must match that of the front edge (e.g. where a bullnosed window board is installed, the side returns must be bullnosed and finished ready for decoration).

Unless otherwise specified, the window boards should project a minimum of 30-40mm from the face of the finished wall.

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Good Practice Guide

11. First fix (carpentry, M&E services, drylining, fire stopping and windows)

M&E Services Plumbing and heating Plumbing and heating pipework shall be installed to a workmanlike standard and take into account all current building regulations, gas regulations, CIBSE (Chartered Institution of Building Services Engineers) and MCS (Microgeneration Certification Scheme) guidance.

All insulated pipework should be installed in a way that ensures that the insulation remains continuous in its length, including at pipe fixing locations and fittings. Direct clipping of pipes should be avoided, as this introduces a break in the insulation at every clip. NHBC Standards 2024 now require all pipework in intermediate floors to be fully insulated including valves and fittings.

Good examples of pipes supported by the clipping of the insulation using munsen rings, oversized pipe clips or waste pipe clips are shown below. This is also important on cold water pipes to maintain a continuous vapour barrier to avoid condensation.

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In these images, care has been taken to install a neat pipe and cable support system.

In this image, care has been taken to maintain the insulation at wall pipe supports within a utility cupboard.

In this example, proprietary, insulated valve jackets have been used to maintain continuity of insulation through the valves.

This is unacceptable. The pre-insulated pipe is cut at every pipe support location.

Below photos is a good example where effort and care has been taken to insulate the entire pipe run, including fittings. Duct tape should however not be used, as it dries out over time and falls off.

Long stem valves (or extension stems) should be installed where insulation thickness might otherwise have to be cut to accommodate a standard valve lever.

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Good Practice Guide

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This demonstrates the foresight and care taken by the dry liner and plumber to install a rip of plastered ceiling board ahead of the plumbing installation to maintain a neat finish when the pipes are subsequently drilled and installed. The pipe insulation is maintained throughout the penetration.

In this image, no attempt has been made to insulate the pipe fittings, some of which have electrical cables in contact with hot pipes (which must never be allowed to happen).

Neatness and excellent setting out is required and evident here.

Here we have an improvement on the previous photograph as the pipework is supported using munsen rings wrapped around the insulation.

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This is a similar scenario, but it incorporates a ceiling access panel and very thick pipe insulation.

The pipes are all temporarily capped or sealed to prevent contamination – something that should always be done to pipes, drainage and ventilation ducts.

In this image, the pipe insulation has incorrectly not been run continuously and stops either side of the fire bat.

Testing of pipework All pipework should be pressure-tested -in accordance with the specification / pipe manufacturer’s instructions. This should be recorded on the Hill QA system.

In these images, the pipe insulation has been correctly run continuously through letter box openings that form the fire compartmentation.

An intumescent fire wrap will seal any combustible insulation (if used), or a gap seal will seal against any stonewool insulation used.

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Good Practice Guide

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Neat bathroom 1st fix installations, with pipework supported and capped off.

The junction between the tiled wall and the shower tray or bath is the most vulnerable location for water leaks to occur. Proprietary sealing tape should always be applied at this junction and subsequently tiled over. This is then finished by a neat silicone mastic joint.

SVP installation

In accordance with Hill’s technical policy, Marley dBlue acoustic drainage has been used along with rubber line acoustic supports where an offset occurs to reduce the potential for noise complaints.

A good example of well supported SVP using an independent Unistrut support system. Also note that the waste pipe connections are temporarily sealed to prevent contamination of the system.

Here a fibre insulation has been wrapped around the drainage at the clip location. This enhances the acoustic absorption and also permits expansion and contraction of the pipe.

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Ventilation Key issues to look out for: y Ensure that ductwork is securely supported no greater than every 750mm. (Unless manufacturers instructions differ). y Flexible ductwork is limited to 300mm straight lengths.

An example of good use of rigid transition pieces and ductwork, limiting the use of flexible ducting to short straight lengths. In this image, the duct should also be temporarily bagged or sealed with tape.

y Flexible ductwork is robust and not tumble dryer hose. y Open ends of ductwork are temporarily sealed to prevent dust contamination of the system. y Ventilation installation is carried out by a registered competent contractor (Competent Persons Scheme). Refer to Hill technical policy BQ034 y Intake supply ductwork is insulated within warm spaces and extract systems are insulated within cold spaces.

Here we see well-supported ductwork using rigid sections, bends and transitions. Flexible ducting is only used for the final straight connection.

In this poor example, the flexible ductwork is not limited to straight lengths and restricts the airflow. This is not acceptable.

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Good Practice Guide

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A good example of temporary sealing of ductwork to prevent dust contamination.

In these examples, this very poor installation has resulted from a lack of planning and coordination between the first and second fix operations, resulting in highly restricted air flow and performance of the system. This will increase fan wear and noise.

Good use of pre-formed ventilation ceiling panel with duct drops. Creating a very neat ceiling interface and duct drop finish.

Good example of well-coordinated duct installation, presenting a neat and wellpresented finished product.

Here are some examples of unacceptable use of lightweight tumble dryer type hoses that are over length and not straight.

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Technical images source: nhbc-standards.co.uk

timber framing line the enclosure and wrap the pipe with 25mm Electrical first-fix installations must be neat and adequately supported. High-level cabling mustwool be unfaced mineral (min. density of 10kg/m3) clipped with metal clips to all areas where unsupported, in metal trays or within joists, to prevent them collapsing in the event of a fire. the material of the enclosure should have a mass of To prevent accidental damage or electrocution during occupation, cables must be fixed in safe zones or H 15kg/m2 landing physically protected where they are within 50mm of the wall face or 50mm from the top or bottom of ceiling / floor joists.

H

Diagram 1 - wash basin

Where the cable cannot easily be located though use of an outlet (e.g. an external wall light with the min.

300mm min. cable running internally), physical protection should300mm be applied. pitch line

Consumer units should be located so that they are between 1350mm – 1450mm above FFL when measured to the centre of the miniature circuit breakers MCBs. In the case of duplex consumer units, the timber framing lower MCBs must be located between the enclosure and 1350mm – 1450mm line above finished floor wrap the pipe with 25mm unfaced mineral wool level as shown opposite.

verticallyWB or horizontally to switch or outlet Electrical accessory ELEVATION

in shaded zone 150mm wide

e.g. socket, switch consumer unit etc.

Diagram 2 - sink 300mm min.

300mm min.

(min. density of 10kg/m3)

landing

landing

g

sure and with 25mm ral wool ing10kg/m3) of

losure and f the enclosure pe with 25mm aneral mass of wool y of 10kg/m3)

Consumer units should also be the material of the enclosure should have a mass of an positioned no less than 300mm from 15kg/m2 internal corner, when measured to the Diagram 1 - wash basin centre line of the MCBs. 300mm min.

300mm min.

Diagram 1 - wash basin 300mm min.

worktop 300mm min.

WB

d zone wide

consumer unit etc.

WB Electrical accessory e.g. socket, switch consumer unit etc.

ELEVATION

Diagram 2 - sink 300mm min.

300mm min.

300mm min.

drainer

Sockets should not be located within 300mm of wash basins or sinks as shown in Diagram 1 and 2.

Sockets should not be located within 100mm of a cooking hob as shown in Diagram 3.

300mm min.

100mm min.

100mm min.

ELEVATION 300mm min.

300mm min.

ELEVATION 300mm min.

300mm min.

worktop

sink

Sockets, switches and controls must be located between 450mm and 1200mm when measured PLAN from the floor and no less than 300mm from an internal corner.

Diagram 3 - Hob

Diagram 2 - sink

of the enclosure e a mass of

one e

accessory inElectrical shaded zone e.g. socket, 150mm wide switch

vertically or horizontally ELEVATION to switch or outlet

worktop

ELEVATION

Residential buildings >18m 300mm min.or including student 300mm min. accommodation or care facilities must include arc fault detection devices (AFDDs) installed on all power circuits.

sink

ELEVATION 100mm min.

100mm min.

drainer

PLAN sink

PLAN

worktop

hob

drainer PLAN

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A neat electrical installation within a utility cupboard using trunking.

A neat installation with cables all run vertically within the safe zones created by the outlets.

Neat cabling installed within the safe zone created by this large media outlet.

A suitable plywood has been installed here to provide a solid fixing for a pendant light.

Good use of metal protective capping to cables where they are outside the safe zone.

A neat and tidy installation within a metal stud partition.

All sockets level and in alignment with rubber gromets installed to all knock outs.

Here the cables have been fixed to a ceiling joist at least 50mm from the bottom of the joist.

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An example of unacceptable and potentially unsafe works, with cables installed outside the recognised safe zone (horizontally and vertically established by the outlet).

In these poor examples, the electrician has compromised the fire integrity of the wall by damaging the wall board.

Air Source Heat Pumps (ASHPs) ASHPs are relatively new domestic heating and hotwater energy systems and as with all things new, an understanding and appreciation of low temperature ASHP systems will be necessary to have an long lasting, efficient and productive system.

Because ASHP’s work to deliver hot water at a much lower temperatures than gas boilers (45/50°C degrees or lower compared to 70°C for a gas boiler) we need to protect the heat that is produced by the heat pump and eliminate as many losses as possible so that this heat is then usable.

Key issues that affect the performance of an ASHP system are: Design:- the designer of the system must accurately determine the heat losses from the home and size the ASHP, water storage cylinder and heat emitters (radiators or underfloor) correctly as both under and over sizing of any elements of the system will impact on performance and efficiency. Heat emitters should be designed such that the flow and return temperatures are 45°C and 40°C respectively.

Accredited designer & installer:- the system designer and installer should be accredited through a recognised agency, such as the Microgeneration Certification Scheme (MCS).

Installation of the ASHP: This should be installed on a robust foundation with provision for condensate drainage, anti-vibration mounts and the unit MUST be installed level to prevent premature wear to fan bearings. The Hill standard detail should be followed.

Exclusion Zones:- Manufacturer’s instructions must be followed in relation to specified ‘exclusion zones’ around the ASHP. This will restrict the location of valves and walls / screens that may affect air flow across the unit to ensure that cold air is dispersed, preventing the creation of a localised cold micro-climate, that will effect performance of the system.

Pipe insulation:- Any un-insulated or inadequately insulated pipes, valves or fittings, whether through gaps, splits not being sealed or incorrect thickness will result in poor heating of the property, extremely high electricity bills and an unacceptable customer experience.

Condense pipes:- These should be short runs, installed in accordance with manufacturer’s instructions to prevent freezing in cold weather.

Flushing and bleeding:- it is important that the system is fully flushed and deaerated using a filling station (pump set). Glycol, added to the primary system as an inhibiter / anti-freeze, reacts with air to produce a brown sludge. It is therefore vital that all air is removed from the system.

Heating controls:- Due to the low temperature of these systems, the ability to heat a cylinder of cold water, or a cold space will be very much extended compared to a gas boiler system. It should therefore be commissioned to operate at a steady constant temperature rather than ‘off and on’.

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Good Practice Guide

11. First fix (carpentry, M&E services, drylining, fire stopping and windows)

Internal Drylined Walls System

Boarding

Many internal walls within houses and most of the walls within RC framed apartments are constructed from plasterboard drywall systems.

Walls (and ceiling) boards may be specified to meet any of the following performance requirements: sound, moisture and fire. It is good practice not to mix board types within a given wall unless detailed to be so constructed.

These must be constructed to a high standard to ensure that the finished walls are straight, plumb, square to corners and finished ready to receive the direct application of paint. They should also be constructed to resist the potential for future movement or cracking.

In addition, these walls often perform one of more other critical functions, including; y Forming a fire resisting compartment wall/ structural fire protection. y Creating a thermal barrier between warm and cold spaces/elements. y Providing acoustic insulation to sound sensitive environments.

Drylining must always be constructed as a ‘system’ and not a ‘pick and mix’ assortment of materials.

Failure to construct drylined walls correctly may compromise performance of the wall and reference should always be made to the detailing and construction requirements stipulated by the system provider.

Where multiple layers of boards are required, particularly where installed for fire performance, it is important that each layer is fully fixed independently of preceding or subsequent layers.

A double boarded fire compartment wall relies of each board layer to face the fire in turn and remain in place for the tested period.

Plasterboard screwed to studs must be screwed at a maximum 300mm centres and 200mm to external corners. Screws must be slightly recessed but the flange of the screw should not break the paper face of the board.

Importance of screw depth into plasterboard Bad – screw is too deep and had gone beyond the paper face.

Good – screw just recessed into board with the paper face unbroken.

The screws fixing the multiple layers of board at the correct centres can clearly be seen from the reverse side

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Boards may be finished with wet plaster or taped and jointed. Both systems have advantages and disadvantages and should both be finished to a comparable standard to walls. On ceilings, taping and jointing may cause small humps at the board short edge, butt joint locations, which may be visible when light shines across the ceiling.

Board joints and screws must be taped and filled with jointing compound/plaster to achieve the specified fire and acoustic performance, even where these are above ceilings.

Dot and dab linings A common method of finishing concrete or masonry walls is to bond plasterboard to the face using adhesive dabs.

Where the ‘dot and dab’ method of bonding plasterboard is adopted, it is important that these are correctly applied as noted below: Indiviual dabs to be approx. 250mm long by 50mm wide at 300mm centres

See table below for number of vertical dabs required

Dabs per 1200mm wide board Board thickness

Dabs

9mm

Four vertical rows of dabs

12.5mm

Three vertical rows of dabs

15mm

Three vertical rows of dabs

It is important that the building is weather tight and the substrate masonry is reasonably dry and free from damp (<16% moisture content) prior to progressing the dot and dab boarding. If this is not achieved, there is an increased risk of black mould damaging the boards.

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Partition deflection head detail completed, with all joints taped and jointed above the ceiling level before the ceiling framing installation, to provide a full smoke seal to the partition.

In this example, the short infill return has been missed to a three-side letterbox. This detail is incorrectly formed and provides an inadequate fire seal to the reveal boards within the letterbox.

Here the head track is assembled to the core board deflection detail on the ground and mastic fire sealant applied before being fixed to the soffit.

The head track on this three-sided letterbox service opening is correctly formed with a short return across the twin wall studs.

All boards are sealed to the concrete slab and tightly butted together.

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Plasterboard is cut to avoid joints along the lines of door jambs as these are liable to crack.

Boards are fixed at a max 300mm centres (200mm to external corners).

Here, we see partition walls located ahead of the underfloor-heating pipework installation, enabling pipework to run through doorways and avoid potential penetration through drilling.

Twin wall party walls are taken to the structure and screeded. Thought has been given to providing a lap to the two layers of board with a metal fixing strip inserted to maintain the fire and acoustic wall properties. Acoustic foam is also installed between the screed and structural floor, columns and partition.

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Good Practice Guide

11. First fix (carpentry, M&E services, drylining, fire stopping and windows)

Fire Stopping The Hill policy is that all holes and service penetrations must be fire stopped regardless of size and this must be carried out by a specialist fire stopping contractor (unless cast into concrete framed buildings). This policy is significantly higher than minimum regulatory standards.

Service installations and particularly ‘letter box’ penetrations should be well coordinated to ensure the insulated pipes remain within prescribed distances apart from each other and also from the perimeter of the opening.

Use of a letter box service entry template ensures consistency and compliance.

Here are some good examples of fire stopping of a three-sided letter box where services have been located no closer then 50mm from any perimeter or between services and pipe insulation has correctly been extended continuously through the wall. A QA sticker is also clearly visible from the installing specialist fire stopper.

Graphite sealant has been used to plastic sprinkler pipes.

In this image, plasterboard baffle boxes have been used to provide enhanced sound insulation between two dwellings, due to the sockets being back-to-back across a party wall, which is bad practise and should be avoided.

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Raising the bar even further with long-stem valves also used in this installation to ensure that the thermal insulation is not discontinued at valve locations in order to operate the lever.

An intumescent wrap and compound have been installed to this SVP penetration as an alternative to a cast in sleeve.

Here a duct has an intumescent fire sleeve installed where it passes through a compartment wall.

In this example, the fire stopping has been correctly completed, however, the pipe insulation should have been run continuously through the fire batt and fire-sealed to the insulation with a suitable, tested material.

Cast in intumescent seals should be provided on reinforced, concrete-framed projects.

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Good Practice Guide

11. First fix (carpentry, M&E services, drylining, fire stopping and windows)

This is a neat job and is being referenced for a QA digital record. The large square holes around the cables indicate, however, that the plasterboard was cut oversized or damaged, as a 10mm bead of fire sealant is all that is typically required around cable penetrations, including multiple cable bundles. This is a costly detail to overcome poor workmanship when cutting the service holes.

Another good intumescent wrap installed around a plastic ventilation duct through a drywall partition.

Here we see a good example of two service penetrations through a masonry compartment wall where surface-mounted intumescent collars have been installed with fixing lugs all correctly fixed.

On the face of it, this looks like a good job, but it is not acceptable as the conduit sleeve is plastic and will simply melt away, negating the fire seal at the end of the conduit. The structural hole is also oversized requiring excessive fire sealant. The anulus should be circa 10mm.

In this example, a surface-mounted collar has been installed around a plastic SVP penetrating a PCC floor plank. All fixing lugs are securely fixed.

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Where plastic conduits are used, these must be finished flush with the plasterboard wall face so that a good fire seal is provided.

Windows Windows should be fixed on all four sides at a maximin 600mm centre, horizontally or vertically, and be between 150mm and 250mm from an external corner. (Unless otherwise specified by the window manufacturers.)

In this image good practice has been adopted and the cavity closer has been sealed with mastic to enhance the airtightness of the home.

There should be a minimum of two fixings on each jamb and sill, and they should be a minimum of 150 mm from the centre line of a mullion or transom.

The above is general guidance as the number and spacing of fixings depends upon the frame width and frame material. The manufacturer’s instructions should be followed.

Where fixing straps are used, these should slope slightly downwards (inside to outside) as in the image below, to avoid the potential for water ingress.

Door cills should be solidly supported to resist deflection when stood on.

In this image, care has been taken to ensure that the underside of the ground floor French doors have been mastic sealed.

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Good Practice Guide

11. First fix (carpentry, M&E services, drylining, fire stopping and windows)

This is very good practice, as a folded upstand has been formed within the cill to provide a stop end and also a solid face to mastic the joint between the wall and cill.

This photograph demonstrates how vulnerable wide cills are to water ingress where they rely solely on a mastic joint. It is unreasonable to expect mastic to bond to a cill in this way and to withstand the expansion and contraction that this cill will experience. An upstand should be produced with a catchment cavity tray installed below.

A neat window installation with protection applied to the stone cill and window extrusions.

An example of neat installation and mastic work.

Pre-plaster hold point inspection The Hill Group QA procedures requires all homes to receive a pre-plaster inspection prior to closing up works. This inspection is to be carried out when masonry walls, windows, first side plasterboarding, services first fix, carpentry first fix and all fire stopping is complete. The aim of this is to hold the closing up of walls and ceilings along with all subsequent build operations until this stage is signed off, defect-free. It is therefore a ‘hold point’ as works should not progress beyond this point until signed off.

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12. Second fix (carpentry, kitchens and M&E)

We are now at a stage where finished quality internal works are being installed.

This is when many homeowners and visitors will judge the quality of the builder.

Attention to detail will make all the difference at this time.

Second fix carpentry It is important that second fix carpentry elements are completed with care, attention to detail and without reliance on subsequent decoration trades to overcome a poor level of finish.

In this image, we can see good on-site quality control with a 2mm fire door margin to the frame being checked by a gap width gauge and recorded on the digital QA platform.

Neat, consistent door margins.

Excellent examples of the neat cutting and finishing of door furniture.

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Good Practice Guide

12. Second fix (carpentry, kitchens and M&E)

In these examples, stair string and landing skirtings have been installed to an apartment staircase. The carpenter has 'expressed' the joint between components by introducing a ‘vee’ joint. This chamfer has also been created to the exposed top of the MDF (and where visible on stair strings, the bottom of the MDF). This attention to detail creates a robust solution that is easier to finish to a high standard and conceals inevitable cracking that will occur between each element.

The wall and skirting are nice and straight.

The ‘vee’ joint between the string and landing skirting is also a good way to abut materials of different thickness, as seen here.

In these images, the carpenter has overcome a co-ordination issue between the skirting and the window jamb by neatly returning the moulding down to the end of the skirting.

Neat cutting of skirting mitres; the wall and skirting have both been finished square.

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In this example, the carpenter has partially mitred the architrave and skirting to maintain the groove across the architrave and skirting – showing great workmanship and attention to detail.

In this example, the hanging rail height is set by the depth of the intermediate support bracket and the use of standard skirting is not deep enough. Care should have been taken to install an alternative deeper shelf support.

In this example, the window board is not deep enough to adequately project in front of the wall face.

Here we see a good quality architrave installation, with an even 5-10mm margin between the frame and architrave. The image also shows tight fitting, accurately cut mitred joints.

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Good Practice Guide

12. Second fix (carpentry, kitchens and M&E)

Here we have neatly finished hardwood boards masking the bracketry under windows.

A maximum of 15mm step is permitted if an accessible threshold is required.

A neat finish to this newel and half newel detail.

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A neatly constructed fitted wardrobe.

Kitchens They say that the kitchen is the heart of the home. It is important that we create a strong heart for our homes, with care taken in not just the cabinetry but also the M&E systems that integrate with this.

In these images we can see that the plumber has taken care and pride in their installation, with pipework neatly installed and clipped.

Decorative cover collars have been provided to pipe penetrations, including the waste pipe.

The waste system and traps are very neatly installed to provide the least intrusion possible within the cupboard space.

Through thoughtful plumbing, the carpenter/ kitchen fitter has also taken great care to neatly cut and install the middle shelf, providing valuable additional storage space to the occupier.

Holes have been neatly drilled to enable the pipework to enter the cupboard.

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Good Practice Guide

12. Second fix (carpentry, kitchens and M&E)

In these images, it is impressive that the plumber has really thought about where to run the hot, cold and waste pipes. The installation is in progress, but note how the vertical waste is right to the back of the unit, how neatly the holes have been formed in the back of the unit and how well installed the hot and cold pipework is.

Here the carpenter has done a neat job in cutting out the shelf to accommodate pipework and waste pipes. The plumber could have potentially improved their installation and taken the waste to the back of the unit, avoiding such deep cut outs.

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These images clearly show the work of someone who takes pride in what they do.

In these examples, the shelf has been severely weakened as a result of poor setting out and lack of care; the incoming water main is located completely inappropriately at the front of the unit.

In this image, the shelf has been weakened to a point where is it likely to break as the plumber has brought the waste fittings forward, rather than to the rear or the side.

Benchmarking is important to set a standard that encourages the plumbers to plan pipe routes in these confined spaces.

In these kitchens, no attempt was made to cut and re-install the shelf to the sink base unit, depriving the occupier of valuable storage space. Leaving the shelf brackets in place only adds insult to injury – it might as well say “look what you could have won, if only we cared.”

An example of how to fill a useful storage cupboard with pipework and waste pipes, including another mains water pipe badly located. All avoidable with care and pride.

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A neat kitchen installation, with all units, door and drawer fronts in alignment with even gap widths.

Island unit extract system installed without a vent. The extractor will not work as it cannot exhaust the air.

Neat granite work can be seen here, jointing this splashback.

1 00

Second fix plumbing When doing second fix plumbing, we are looking for functionality as well as neatness and pride taken by the installing tradesperson.

Starting with works within a cylinder cupboard, we see here a very high quality installation, with insulation carried out to a good standard, with all valves nicely labelled. This looks like someone with skill, care and pride in what they do has been at work.

Note that brassware to the cylinder is fully insulated to prevent heat loss/overheating.

Could it be improved upon? Yes, as the valves remain uninsulated, and electrical insulation tape should not be used. Foam tape or a suitable adhevsive specified by the manufacturer should be used.

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In these examples, insulation pipes are uninsulated where clipped and little effort has been taken to insulate brass fittings to the cylinder and other components. This will be the source of heat loss and energy inefficiency and overheating as well as looking poor.

1 02

Does this quality of insulation look to have been carried out by a competent tradesperson who takes pride in their job?

We must do better than this.

This is a work in progress but the pipework is neat and the HIU is protected with the pressure relief tundish within 600mm of the appliance.

Very neat, quality work with distribution pipework.

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In this installation the underfloor heating manifold has been neatly hidden within this boxing and access panel.

The gutter/downpipe fitting has been twice screwed to the fascia board.

Pipes neatly run and terminate into the partition wall, finished with white collars.

Here we see a novel way of providing additional stability to the stop end of gutter, by running the gutter across the downpipe fitting and carefully core drilling a hole in the gutter, providing added support to the end of the gutter.

Downpipes secured to wall and black screw caps fitted to conceal the heads of the screws.

1 04

In this example, metal gutters and downpipes were installed very neatly to meet local planning restrictions.

Here we see an unacceptable installation, with elements of the brass valve exposed to the cold air. An insulated valve jacket should be fixed here.

A neat dry riser installation.

Neat insulation to these air source heat pump installations, with valves and fittings insulated.

Good use of insulated valve jackets here.

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Good Practice Guide

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Here the sockets are unevenly spaced and too close to make a decent job of finishing the wall – unacceptable.

Second fix electrical A neat finish is important to sockets and switches – care and attention is needed to ensure that these are level, aligned to each other and evenly spaced.

Aim for a design gap of no less than 30mm between outlets, to enable a consistent neat wall finish to be achieved.

1 06

300

Tiled Skirting

300

Timber skirting

300

300

300

Our standard bathroom details indicate that the spur outlet is to be located to align with the bottom of the towel rail, close to the side where the electrical heater is located. Where this is not possible, it should be located under the towel rail.

Ti

Here we see the bathroom towel rail electric heater neatly installed with a short flex terminated in a spur outlet.

Another example where the spur is wrongly located, resulting in a long and untidy electrical flexible cord. It should be located outside the right hand side of the radiator, with the bottom of the outlet level with the radiator (300mm AFFL).

In this example, the cable is neatly clipped to the skirting.

There appears to have been a co-ordination issue here as the thermostatic towel rail heater should ideally be located to the right of the radiator. The towel rail should also not be adjacent to the WC. The spur is too far from the heater, resulting in a very long length of flexible cord.

In this example, the spur is wrongly located.

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Consumer unit installation To provide both accessibility and safety for young persons, consumer unit switches must be mounted between 1350mm – 1450mm from floor level

This is to be measured to the top of the toggle switch in the up (on) position.

Where double row ‘duplex’ boards are installed, this is to be measured to the lower bank of switches.

Here we see good use of neat, printed circuit labels rather than individual selfadhesive labels supplied with the consumer unit.

Whilst this is compliant, the self-adhesive labels supplied with the consumer units along with handwritten labels are not as professional. Printed labels should be used. Circuit 8 is unlabelled and the two lighting circuits are not described.

Whilst no longer required under current regulations, our Hill preference is that these labels should still be affixed to the consumer unit. Please discuss with your electrician.

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A neat installation in progress. All sockets carefully set out with identical margins between them.

Good quality completed work.

A neat meter and incoming electrical supply installation.

Ventilation In these examples neatly installed MVHR units have straight ducts finished to the ceiling.

Extract ducts should always be insulated where they pass through cold, unheated spaces as the warm, moist air could condense on the cold surface of the duct. Here we see the duct has been insulated, however the terminal and transition ductwork have not.

The insulation must continue to the underside of the roof underlay.

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Good Practice Guide

13. Finishes

Pre-decoration hold point inspection The Hill Group QA procedures requires all homes to receive a pre-decoration inspection prior to the commencement of decoration works.

This inspection is to immediately precede commencement of decoration and is intended to ensure that the environmental conditions are

satisfactory (the home is clean, dry, warm and ventilated) and surfaces have been checked for completeness and defects so that substandard decorating work is avoided.

To avoid the cost and delay associated with re-work, this ‘hold point’ inspection must be signed off prior to commencing any decoration.

Decoration The painting and decorating of our homes is one of the most important finishing trades. It is the final surface that the occupier sees and touches and the impression this creates will be an important factor in determining how the quality of our homes will be judged.

Reference should be made to the Hill Group Painting and Decoration Materials and Workmanship Specification.

Pre-Decoration Painting and decorating must not commence until the ‘Predecoration hold point’ quality inspection is completed. This ensures that the surfaces to be decorated are smooth, flat, level, plumb and square before decoration commences.

It is also important to ensure that surfaces are dry (moisture content <16%) prior to decoration, that heating is on and the general humidity within the home is low (less than 80% RH and ideally close to 65%). During the drying process, water-based emulsion paints will add significant amounts of moisture to the air, and it is important to provide adequate ventilation to remove this moisture from within the home.

Prior to decoration commencing, it is also important to vacuum the area to remove dust that may contaminate and spoil freshly painted surfaces.

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Preparation y Knotting: Whilst most skirting, architrave and window boards are made from mdf these days, some of our clients still require solid natural timber. In addition, curtain battens, door edges and many door linings are made from softwood. Where these contain knots, specialist knot sealers should be used to hold back resin, tannin and other stains, which could discolour wood coatings on some wood species. This should be applied after rubbing down and prior to the application of primer. y Surfaces not intended to be coated, including floors, furniture and factory-finished components and fittings, should be protected against splashing and spilling of painter’s materials or other damage. y Surfaces should be abraded to remove debris, create a smooth surface, or improve paint adhesion. y An appropriate grade of abrasive paper should be used according to the surface being prepared; excessively course grades can damage the wood fibres, impairing the appearance and possibly the performance of the paint system. Wood surfaces should be sanded in the direction of, and not across, the grain without using excessive pressure, which can damage the wood fibres. Arris edges should be rounded off to ensure good paint adhesion. y When painting mdf, initial coats will often raise fibres to edges (typical on window boards and architraves). These will need to be rubbed down between coats to achieve a smooth finish.

y For surfaces which have been dry-abraded, dusting or vacuum-cleaning should be undertaken. Dust and dirt should be removed before painting otherwise the appearance and performance of coatings will be impaired.

A tack rag should be used to finish off the cleaning process. y Stopping and filling should be carried out as early in the preparation process as the type of material used and the nature of the substrate allow. Many materials used for stopping and filling are absorbent and if applied late in the process, can cause sinkage and variations in gloss, sheen or colour. y Nail, pin and screw heads should be punched or countersunk for stopping, with heads normally not less than 2mm below the surface. Waterborne and two-part fillers should be abraded when dry or cured. y Plaster: Dirt and loose surface deposits should be removed by dry brushing. Plaster nibs and splashes should be scraped off, care being taken to avoid damaging the surface. Cracks, holes and surface imperfections should be stopped and filled with a water mixed filler before the application of the first or priming coats. y Plasterboard: Dirt and loose surface deposits, especially dust from sanding of filled joints, should be removed by dry brushing. Filler nibs and splashes should be scraped off, care being taken to avoid damaging the surface. Cracks, holes and surface imperfections should be stopped and filled with a water-mixed filler before application of first or priming coats. The correct grade of filler should be used for filling holes whilst a fine surface filler should be used for smoothing shallow dips.

Sequencing and timing Each coat in the system should be dry throughout its thickness before the next coat is applied. Except with coating materials formulated for lengthy exposure without further coats, such as some primers, intervals between coats should not exceed a few days, otherwise adhesion might be impaired.

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Good Practice Guide

13. Finishes Common Painting defects Defect

Typical Cause

Remedial Treatment

Bleeding

Solvent or water reactive or extractable stain, timber extractives, tar or bitumen.

Remove as much contamination as possible, seal with stain block primer, alkali-resisting primer or aluminium wood primer.

Blooming or milky appearance, usually on gloss paint, also slight matting of the gloss

Cold temperature, high humidity and/or moisture during the drying process of the paint. Usually associated with winter months.

Abrade and recoat.

Ropiness (brush marks)

Poor flow of the paint, over brushing, rapid drying etc.

Abrade and recoat.

Cissing or fish eyes (appearance of voids in paint film whilst wet)

Surface contamination, wax or greasecan also occur when applying incompatible paint over a poorly prepared surface, e.g. water-borne paint over oilbased paint.

Remove as much contamination as possible, degrease, abrade thoroughly and re-coat. Ensure application tool is also free from contamination.

Sleepy gloss (low sheen)

Contamination, e.g. wax or sinkage into substrate due to incorrect or insufficient primer or undercoat.

For mdf, abrade and then apply a water-born acrylic primer, then recoat. Other surfaces might simply require recoating.

Halo effect (flashing arising where paint has been touched up)

Trying to ‘touch up’ areas, especially sheen paints, but can occur with all paints.

Re-paint the whole area or to the nearest visible cut-off point.

Flashing

Losing the wet edge of the paint during application.

Re-paint the whole area or to the nearest visible cut-off point, ensuring the wet edge is maintained. For water-borne paints only, reduce ventilation and airflow so that humidity is increased to assist with extending wet edge time.

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Common Painting defects Defect

Typical Cause

Remedial Treatment

Roller marking (visible marks between tracks of the roller)

Roller stipple folding over in a different way depending on whether application was an upstroke or a downstroke. Often only visible when viewed under oblique lighting conditions.

More noticeable when the wet edge has started to dry.

Re-paint the whole area or to the nearest visible cut-off point, ensuring the wet edge is maintained. Lay off in one direction. Possibly thin waterborne paint so that roller stipple flows out more readily.

Curtains, runs, sagging, floatation of pigment

Over application, i.e. too much paint applied unevenly.

Allow excessively thick areas to harden, sometimes scraping off excess thickness will be required.

Abrade and re-coat.

Cracking / crazing

Usually associated with applying a fairly brittle paint over a highly flexible layer, i.e. mall over silk.

Abrade, correctly prime, (using primer) and recoat. Severe instances might require lining paper.

Pickling (looks like wrinkling)

Solvent attack, i.e. applying chlorinated rubber paint over conventional paint. Solvents act as a stripper.

Complete removal of all affected coatings might be required.

Wrinkling, rivelling, shrivelling

Application too thick, usually gloss paints. The paint layer skins over but remains wet underneath. This can also be caused by overcoating before previous layer is dry.

Allow affected areas to harden, then abrade with wet and dry abrasive paper to smooth and re-coat.

Bittiness

Contaminated paint, dusty atmosphere, substrate not clean, application tool not clean.

Abrade, recoat, ensure application tools are clean, strain the paint.

Orange peel effect

Application by roller without laying off the paint with a brush (such as applying gloss to doors). Poor atomization when spraying.

Wet abrade to smooth and recoat using correct method and adjustment.

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Good Practice Guide

13. Finishes Bathrooms and cloakrooms Bathrooms and cloakrooms are not just functional spaces. They often bring together many different trades, working in close co-operation and coordination to complete the quality of finished bathrooms and cloakrooms that our customers expect within their new home.

A neatly finished wash basin cabinet with consistent joint gaps between drawer fronts.

Wall tiling is set out to the centreline of the wash basin mixer tap. Neat finishing of mastic pointing is critical to these areas.

Here we can see a tiler using a proprietary tile levelling system to ensure that these large tiles all sit level with flush joints.

Here we have a WC neatly installed with carefully applied mastic pointing all around.

The wall tiling has been set out to centre line with the WC. A tiled boxing has been well-finished to conceal the waste pipe. This includes a polished metal tile trim to match the general specification of this bathroom.

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Neat mastic work around this WC and a contrasting dark grey mastic to the waste pipe boxing.

Here we can see a bath filled to the overflow level, to check for leaks at the overflow or waste connection. Keeping the bath filled will also ensure that any settlement due to the weight of water occurs prior to the application of the mastic joint around the bath.

This image shows good co-ordination to ensure that the tiling joint has been centred to the bath tap and shower rail. A neat junction was achieved between the two coloured mastics in the corner of the bath.

In this image the setting out of the tiling was determined by our client, who wanted to see equal sized cuts to the internal corners within the bath. Two different coloured mastics were used between the tiles at the internal corner and abutting the bath.

Further example of neat work where care and attention to detail have been demonstrated.

Here the plumber has used chrome collars to match the chrome towel rail. Pipework has been decorated in silver grey paint.

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13. Finishes

Here the client wanted the tile to be centred on the wash hand basin. Care was taken to ensure that the floor tiles followed the same setting out. The semi-recessed wash hand basin has been neatly cut and finished to the vanity boxing.

Here the mastic contractor has taken exceptional care to insert a small section of grey mastic where the tile-to-tile junction occurs.

The tiler has very neatly cut this metal tile trim. Between the tiling and mastic pointing contractor, this is a first-class finish.

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A very sharp neat finish to this contemporary bathroom. Good use of polished metal tile edging and coloured mastic sealant. These porcelain tiles have been carefully cut to suit the shaver point location and WC flush.

All installed shower trays must be level and checked to ensure that water drains, leaving no pooling greater than 200mm in any direction

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Good Practice Guide

13. Finishes

It must be remembered that workmanship and quality are not measured by the cost of the finishes involved. In these examples, excellent quality has been delivered with a basic, affordable specification. Interfaces and details remain sharp and well formed.

In this cloakroom we have neat and tidy finishes with care given to the application of the mastic sealant to sanitaryware and the perimeter of the vinyl flooring.

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General internal areas A great example of care being taken by the tiler to neatly cut out to accommodate these sockets and switches. This has taken great competence due to the very slender sections of tiles remaining.

These images show a well-finished means of escape stair and corridor within an apartment building. Even with the very unforgiving satin gloss wall finish, the walls are clearly smooth and flat.

Outstanding examples of square reveals, good carpentry and a sharp,crisp finish. All carried out by the decoration, flooring and mastic contractor.

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Good Practice Guide

13. Finishes

High quality carpentry, decoration and carpeting combine to deliver an excellent finish to these stairs.

A very neat finish to this contemporary newel post and cap.

Here we have an exemplary standard of finish between the architraves and wall. The architraves were rubbed down so there was no raised grain or fibre and this was also continued across the head of the door.

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This window area benefits from the accuracy of the walls and reveals being perfectly square.

Everything is finished to a high standard here – straight, square, plumb and level.

Great examples of sharp decoration around electrical accessories. No caulking or excessive surface brushing.

This contemporary square edged window board has been very neatly finished. The edges of the window board project 30-40mm and are square with just the arris removed.

Edges are sanded smooth. The window reveal is square and plumb. It’s difficult to see how this could be improved.

Everything being square and plumb was essential to make this look as good as it does.

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13. Finishes

A selection of completed rooms bringing everything together and finished to a very high standard.

A pre-finished loft access door neatly installed and decorated around.

Here, the ceiling downlighters, detectors and vents have been accurately set out to be in alignment (maintaining a minimum 300mm between the smoke detectors and lights, walls and vents).

A faultless floor and skirting installed here and neatly finished with a mastic joint.

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Good Practice Guide

13. Finishes

External finishes External parts of the home are on show for all to see. Not just the owner of the home, but visitors and anyone passing by (including potential new homeowners or clients).

More than anything, the external finish is our shop window. How it looks and performs, not just at the completion of the home, but for the decades or centuries to come will be the legacy all of us will be judged on. It is therefore important that attention to detail and care is applied, if we are to be judged kindly.

Here we have examples of well presented external finishes. y Bricks are clean, undamaged and uniformly blended across the elevation. y Neat leadworks to porches. y Neat herringbone mortar pointing to the porch verge and hip tile. y Neat mastic work to windows. y Downpipes neatly clipped, straight and vertical. y Soft landscaping kept 150mm below DPC level. y Roofs clean. y Service ‘hockey stick’ ducts plumb to the meter cupboards. y Paths and driveways clean.

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A well secured downpipe over the centreline of the movement joint.

A neat window installation with all interfaces and junctions sharp.

A very neat door jamb to wall junction and sealant. Every visitor to this home will notice this if it is sub-standard.

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Good Practice Guide

14. Moisture and mould in new homes What causes mould?

Dampness and mould can occur in homes when water vapour in the air condenses on cold surfaces or the surface is damp with insufficient ventilation and heat to enable this to evaporate.

Moulds are a natural part of our ecosystem. Microscopic spores, invisible to the naked eye, are present in the air, interspersed by dust particles. Problems start when the spores land on surfaces that have excessive moisture.

In occupied homes, water vapour occurs through daily life such as bathing, cooking and breathing, and homes are designed to control this through heating and ventilation.

In newly built homes, damp and mould needs to be controlled, even before the home is completed and occupied.

Mould requires moisture to develop and will only develop where sufficient moisture exists.

Timber joinery and finishes should not be exposed to dampness. Wall, ceilings and floors should have a moisture content less than 16% and ideally between 12-15% prior to storing or installing these elements.

How to control mould prior to completion?

Dampness embedded within the structure of new homes, particularly in traditionally built homes constructed during wet seasons, is unavoidable and it can take up to two years to fully dry from occupation.

What is mould and is it a problem?

Mould is a living organism that proliferates in the indoor environment as long as conditions are favourable. The word ‘mould’ is a collective term for spore-producing hyphomycetes fungi and there are many types of mould.

As soon as possible however, we should strive to remove as much moisture as we can, so that a moisture balanced state is achieved.

Structural elements should be below 16% moisture content and ideally between 12-15%. Plasterboard should be less than this.

The most commonly found moulds are black and green varieties, both of which can be harmful to health. y Green mould typically has a fluffy appearance and is often found growing on damp walls, inside cupboards and on carpets. y Black mould is a more common and a particularly toxic micro fungus variety, stachybotrys chartarum. It is often detected on cellulose-rich building materials in damp buildings.

The areas noted below are particularly prone to mould due to ‘dead air’. Closing-up and fitting of cabinetry should only occur once walls have dried below 16% moisture content.

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Bath panels or boxings

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Built in wardrobes or cupboards

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Areas where cabinets or appliances / spaces occur

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Cupboard spaces

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‘Dead spaces’ where air circulation is limited

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5

Cold still air

Warm ventilated air

Structure born moisture remains.

65% RH

Interior

Exterior

Interior

Exterior

100% RH

Structure born moisture evaporates and is ventilated or condensed via de-humidifiers.

To assist in the drying process and prevent mould growth, the relative humidity (RH) of the air adjacent to the wall, ceiling and floor surfaces, should be maintained below 80% RH and ideally no more than 65% RH. This is measured using a hygrometer.

RH measures the percentage of moisture contained within the air at a given temperature (100% being saturation/dew point).

Warm air can hold more moisture and therefore have a lower RH than colder air with the same amount of water vapour present.

It is therefore important that we have heating on and ventilations systems commissioned in our homes as soon as possible, to raise the internal temperature and thus lower the RH permitting structural moisture to evaporate and be extracted.

This is particularly important in spaces that have limited air movement, such as internal corners or rooms, cupboard and other confined spaces. In these areas where local RH levels are raised, localised fans may be required to move the air.

Where RH levels remain higher than 80%, de-humidifiers should be provided.

Where mould has occurred Where mould has occurred, it is important to note that even if conditions have been improved and its spread has been controlled, the dead spores are still harmful to health (appropriate PPE must therefore be worn when dealing with this). In less severe situations, the mould should be removed with Dulux Trade Weathershield Multi Surface Fungicidal Wash and affected areas recoated with Dulux Trade Mouldshield Vinyl Matt.

In more severe instances the affected area should be removed and replaced.

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Good Practice Guide

15. External works

Paving This section highlights good workmanship when completing external works to our homes.

Here we see considerable care and skill taken in cutting the paving around this manhole cover to achieve such a perfect fit. The thin pieces of paving have to be cut and laid with great care to avoid them breaking.

Neat and tidy finished hard and soft landscaping works.

Another example of a very neatly-finished piece of work incorporating a rainwater gulley.

Neat paving to this approach footpath, including careful diagonal cut paving to accommodate changes in levels.

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Here we see some exceptionally skilled cutting of concrete block paviours to create this gravel margin. This includes very small diagonal cut blocks as well as careful cutting around the rainwater gulley.

16. Material storage, organisation and protection

Material storage It is important that materials are stored to prevent damage or degradation prior or post incorporation into the works.

It is recognised that building sites are often very muddy places with high moisture content internally or where materials are prone to physical damage. Sites in winter often don’t present well due to weather conditions, and we do not expect them to be pristine at these times. Good material storage must however try to prevent damage and wastage.

Here, bricks remain polythene wrapped and the bricks and blocks are all stored off the ground on pallets. The storage area is tidy and safe.

Here we see bricks and blocks protected from inclement weather. This contributes significantly in reducing efflorescence to facework and in relation to inner leaf blockwork, it can also help to reduce the drying times within homes.

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Good Practice Guide

16. Material storage, organisation and protection

Examples of poorly stored bricks that will cause them to become saturate and contaminated in mud. These should be supplied with or transferred onto pallets.

An example of poorly stored roof trusses. In this case, they have been stored flat (when they should be upright supported correctly at the node points) and on the ground (timber must never be stored on the ground). There is also a temporary fence base plate sitting on top!

Good examples of trussed rafters being stored off the ground on scaffold truss racks. This ensures that the lightweight timber trusses are not contaminated by mud or ground moisture, as well as preventing excessive stresses imposed on the timber sections or joints.

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Here we have a large number of roof trusses incorrectly stored directly on the ground by the rafter feet. The trusses can already be seen to be distorting.

An example of how we don’t want to see valuable materials stored on our sites.

The delivery of these trusses must have been predicted – good site management must include making sure you have appropriate storage facilities available for planned deliveries. This is unacceptable.

The facia material in the foreground of the image is also unlikely to be usable after the lack of care in its storage.

Metal web joists stored off the ground on timber bearers.

More incorrectly stored roof trusses.

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Good Practice Guide

16. Material storage, organisation and protection

Site organisation Site offices It is important that sites carry out operations in a certain way and in a specific order for a reason, as directed by our site team. We need to direct these operations.

Benchmark! Establish minimum quality expectations at every opportunity. Make time for them.

Ensure you are in control of every operation on your site, based on a plan.

Make good use of ‘best practice’ walls to communicate topics that have a particular relevance to operations on site.

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Material storage is also very dependant on forward planning and site organisation, to ensure that it is both stored correctly and also that it is manhandled as little as possible once delivered. Moving materials unnecessarily costs money, is potentially hazardous and increases the risk of damage.

Here we have a neat and tidy mortar silo area with good clean access.

On this congested full footprint site in central London, materials management has been key to the success of the project. Materials are scheduled just in time and moved as few times as possible to the final workface.

Thought has been given here to provide safe pedestrian access to the working area, whilst ensuring that the face brickwork is not damaged. Note also the weather jackets protecting the pallets of face bricks from inclement weather and saturation/frost.

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Good Practice Guide

16. Material storage, organisation and protection

Neat and tidy material storage areas. These do not just contribute to health and safety but ensure that our valuable materials remain undamaged and fit for use.

On this busy London apartment project, the M&E contractor has created a secure tidy materials store.

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Here we see some excellent examples of site managers planning and de-risking complex details by constructing mock-up areas to ensure any buildability issues are ironed out before the main works. This sets quality benchmarks that can be consistently applied across the site.

Here the site team have created a benchmark area to demonstrate how the differing fire barriers are to be installed across the various cavity widths and junctions on their site.

In these images we can see where the site team has created designated sub-assembly areas.

These clean and tidy ‘mini workshops’ create a great environment to drive up consistency and quality.

Airing cupboard slatted shelving is being manufactured within the workshop area.

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Good Practice Guide

16. Material storage, organisation and protection

Here we see plumbers manufacturing preformed pipe runs. All consistently made in their own ‘site factory’.

Management of rainwater is very important on new homes to avoid excessive saturation of external walls, leading to potential water ingress, efflorescence and mould growth.

A common problem when using temporary plastic socks is that they can be subject to wind and blow off. This ingenious solution deployed on one of our sites involved tying a knot at the bottom of the sleeve and then piercing the pipe 300mm – 400mm from the bottom. The retained water in the sleeve acts as a weight without causing damage to facework should it be blown against the wall.

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Here we see the impact of inadequate rainwater management on a site.

Protection It is important that constructed works which are vulnerable to damage are suitably protected.

In this section, we highlight good practise in the application of protection.

On this project, industry leading reusable protection has been laid on the scaffold and turned up the brickwork to provide protection to the brickwork from dropping mortar and the commonly seen ‘splash banding’ from scaffold lifts that stain face brickwork.

As an alternative, a band of protection has been applied to the wall immediately above and below the scaffold lift to prevent splash staining. Also note the robust protection to the cills.

Within this heavily trafficked loading area, plywood and softwood protection have been provided to prevent damage to the face brickwork and exposed corners.

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Good Practice Guide

16. Material storage, organisation and protection

Another example of solid robust protection applied to the jambs, head and cill of this highly trafficked vulnerable doorway.

Here we see an example of rigid cordex type plastic sheeting fixed to decorative face brickwork in high traffic areas to prevent damage and staining. Particular attention has been paid to vulnerable external corners.

Here we can see good use of DPC laid over an open cavity to prevent cavity insulation becoming excessively saturated. Also note the plastic caps fitted to the scaffold ledgers where they are in contact with the brickwork, to prevent damage.

A good example of protection of brickwork in progress.

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A window installed retaining the supplied protection.

A higher level of protection has been applied here, due to its increased vulnerability.

Window frames, glazing and cills have been protected here.

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Good Practice Guide

16. Material storage, organisation and protection

Where projecting plinths are detailed, these are protected with DPC.

All stone cills or features must be protected – as a minimum with sacrificial DPC, and more robustly if required, to prevent minor impact damage and mortar staining.

Here, an extended cavity tray has been used to provide temporary protection to a stone feature lintel.

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Here we see a front entrance door protected along with a QR location code, useful to assist in recording QA sheets or issues via our QA system.

Protection must be designed to ensure that it can remain in place as long as possible during construction. In this example the common area staircase doors have been installed to maintain a fire compartment (even during construction operations) and protected so that the door remains fully operative. The risk of impact damage to the door has been deemed low at this stage of construction.

Finished riser fire door sets installed to provide safe lockable restricted access.

Common area staircase balustrade capping protected.

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Good Practice Guide

16. Material storage, organisation and protection

Good re-use of kitchen protection from completed plots.

Internal timber staircases must remain protected and maintained (if the protection becomes damaged or removed).

Windows should be protected internally as well as externally. In this situation a liquidapplied peel-off protection has been applied to the window. It is particularly important that glass remains scratch free.

Here we have examples of pre- and post-tiling protection within the bathroom using heavy duty protective plastic.

A good example of protection applied to a bath.

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Here are examples of very robust protection installed to provide protection to components within a bathroom.

An example where no protection has been provided to this installed bath. It is highly likely that this will suffer damage.

Here the WC and handwash basin have been protected and the floor has re-used kitchen protection from a previously completed plot.

Here we see the floor, sanitaryware and cabinetry protected.

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16. Material storage, organisation and protection

Example of protection to bathroom cabinets/ joinery and shower tray.

Heat interface units, MVHR unit and radiator protection good practice.

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In this image, we can see a bathroom wellprotected prior to sprayed wall and ceiling decoration.

Here the supplied radiator protection has been left in place.

Wardrobe framing and shelving has been installed and protected.

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16. Material storage, organisation and protection

Here we see a kitchen during its installation.

Please note the protection applied to the flooring prior to the kitchen installation.

Once installed, kitchens protection needs careful thought as plumbing, electrical, ceramic tiling, decoration, flooring and white goods all have to be subsequently installed. Ideally the protection should be designed so that it can remain in place for much of this work.

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Worktops, sinks and hobs are particularly vulnerable and should remain protected until the last possible moment.

Worktops must NEVER be used as workbenches or access platforms.

Flooring is particularly vulnerable to dirt and damage; consideration must be given to its protection.

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