WORKSHOP 04 - SHEET & BOARD CLADDING

38 • POWERPANEL R Powerpanel®

brick skin in traditional Australian brick veneer homes. It is a cladding material, nominally 75 mm thick, that is attached to the outside of a timber or metal stud­ framed wall to provide a weatherproof enclosure but not to carry any superim­ posed building loads.

A basic Powerpanel is 600 mm wide and 75 mm thick and comes in various heights (2400 mm or 2700 mm are the most corn-

This product has been developed from the European technology of ultra-lightweight AAC blocks and panels. It is manufactured in Australia by the CSR company AAC is used as a structural load-bearing material in most European applications.

This Australian adaptation-Powerpanel® -is designed specifically to replace the

Drainage of window $ door sills, in either aluminium or timber should be directed to the outside of building, on top of the window sill Soff1t DETAIL SECTION OF HEAD

DETAIL PLAN SECTION OF JAMB Window sill

Timber stud or steel stud frame

man). It stands on its end outside a conven­ tional stud wall frame with the weight of the panel supported on the edge of the floor slab by a subfloor brick wall or on a galvanised steel angle fixed to the base structure.

Folded steel top-hat sections are fixed horizontally to the external face of the studwork. The Powerpanels are then stood vertically against these top-hat sections and fixed through the section into the inter­ nal face of the panel.

The panels are 5-10 mm apart; these joints are fitted with packing rods and then filled to the manufacturer's recommen­ dations to achieve a Vee groove or flush joint. Panels are cut on-site to provide under- and over-window panels.

The panels are coated with sealers, tex­ tures and skins to provide various colours and textures but specifically to provide the panels with weather protection. The build­ ing industry is always looking for a material that costs no more than a clay brick skin to replace bricks in brick veneer homes.

Powerpanel will do this as long as it is coat­ ed with an economic waterproof coating.

However, if a high quality coating is used, Powerpanel may cost more than conventional brick veneer.

Powerpanel may succeed with project home builders, as it is at least as flexible as bricks and can be used with existing house designs with minimum changes to the draw­ ings. OBs should be able to use modestly skilled people and the Powerpanels provide a reasonably sound and thermal barrier skin.

DETAIL SECTION OF SILL Fascia

Gutter -

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---===-=::::::i Timber window frame

--- ;:.==1= ==➔

----

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Tophat section

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.

--

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TYPICAL ELEVATION OF WALL WITHIN WINDOW

Polyurethane full seal up sides of window frame before coating Sloping sill necessary

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Tophat/ .t:: ;::.=:== -.= section, --- ::::=--==--� .i= ::-----=�--- -.:.:: ----- -l' /Top of loor ·--

Soff1t

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I 0mmIcontrol Joint at window fill with polyurethane filler

Tophat section

/Hebel blocks as sill (as required) nailed $ glued to face of hebel panel with thin bed adhesive Power panel

A llow to coat exposed concrete◄ TYPICAL SECTION to match wall

SHEET AND BOARD CLADDINGS • 39 Traditionally timber frames were clad with weatherboards, that is, natural timber boards wrought to a section, generally tapered, that could be fixed in a weathertight lapped method. Weatherboards of this type are still used in some houses, but rising costs and diminishing resources of suitable timbers have caused the traditional weatherboard to be dis­ placed by manufactured reconstituted timber and composite material sheets and boards.

There are many people who now believe that it is easier to insulate a timber framed board or sheet clad wall than it is to insu­ late a brick veneer wall. In fact, some mod­ ern passive energy house designs suggest that a house with an external insulated and sheet clad skin and an internal skin of masonry may give the best compromise on thermally efficient planning.

Other Queensland and the Northern Territory, no Australian State has used board or sheet clad houses to any great extent since WW2. The myth of brick is bet­ ter-nay, best-has developed, along with the notion that boards and sheets must be painted every few years and maintenance is the curse of the homeowner.

Low maintenance boards and sheets are available including natural cedar through to factory finished boards of aluminium. Paints and stains have also improved markedly in the last 20 years. Painting is now much eas­ ier than ever before and the paint life is sig­ nificantly longer-10 year paint frequencies are now not only possible but common.

The product range: Fibrocement (Fibro} Fibro, as this product was dubbed by the Australian community, started out as a grey­ coloured, brittle, thin asbestos fibre rein­ forced cement sheets. It was the product that, after WWII allowed many State Housing Commissions to build cheap mass housing.

Its association with that type of housing gave the product a bad name. Then there was the asbestos scare; asbestos fibres were linked with some deadly cancers.

Today fibrocement has changed. The asbestos has been removed from the wide range of products traditionally reinforced with this material and the replacement fibro­ cement products are believed to pose much lower health risks (a risk that was greatest if the asbestos cement sheets were cut and the asbestos fibres were allowed to become airborne), and are produced in a range of products that have gained wider acceptability than in the past, particularly the wide board planking ranges.

Fibrocement products are sold as a complete system, backed by a wide range of accessories and detailed instruction pamphlets.

Hardboard A product with a similar chequered past to Fibre, Masonite was considered an indoor only product-and only then when there was no better alternative.

DETAIL-WEATHER BOARD CLAD TIMBER FRAME

Modern hardboards are well-developed quality products that include a range of external plankings. These compete with fibrocement planking for a share of the cladding market.

Natural timber Natural timber weatherboards are now considered by many people, including an increasing number of architects, to be a premium cladding product. There is a cer­ tain amount of pride in saying, 'I live in a natural Western Red Cedar home'.

Many timbers can be used to make weatherboards, from native species hard­ woods through local pines to the imported Western Red Cedar and other more exotic species, including Palm Wood.

Timber weatherboards can be used in the traditional horizontal planked method, in a vertical mode or on any other diagonal angle. They can be painted, stained or left natural (certain timber species only).

There are also natural timber shingles and shakes that can be used on walls and are particularly suited to walls that are sloped, as may be found on a mansard roof design.

OBs should take some care when using weatherboards, as some are still manufac­ tured from scarce rainforest and diminish­ ing native timbers. Where possible use only weatherboards sourced from plantation or environmentally managed forests.

COMMON WEATHER BOARD PROFILES '4_; _____':::,_...,.

I rusticated

rafter

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top pla

2 splayed-rebated

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r3 splayed For vertical use For horizontal use For diagonal use

Sarking to face of studs should be 'breating' type fire resistant and where applicable, reflective

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4 sh1plap

c:::::::::::::, 5 double log cabin

--------------� G board and batten

___4 5 6 1 234 5 1 45

CLADDING JOINTING TRIMS 123

39 • SHEET AND BOARD CLADDINGS Aluminium Aluminium is used to manufacture a range of profiled sheets and boards that general­ ly mimic weatherboards, with wood-grain texture on the board surface (fibrocement and hardboard planks also offer wood graining; only natural timber comes free of a deep embossed 'natural timber' look).

Aluminium is a very durable material, but the aluminium used in some aluminium claddings is of a light gauge and therefore likely to be damaged by stones thrown up by lawn mowers and the like.

The coloured finish is applied under fac­ tory-controlled conditions and this gives the finish a very long life, but it is not infi­ nite. At some point in the future an alumini­ um-clad house is going to need repainting; the techniques that are needed to prepare and apply the new finish are beyond the abilities of most OBs. Plastic Plastic-moulded, wood-grained, self­ coloured weatherboards are used exten­ sively in the United States. Some of the products are marketed in Australia but few have had extensive solar testing in the harsh Australian sun. As sun, or more par-

_

ticularly ultraviolet light, is a destroyer of many plastic compounds, take care if you choose a plastic cladding material that you are sure its life expectancy is sufficient under Australian conditions to justify its use.

Fixing methods Most board or sheet products are fixed to the timber frame by the use of nails; non-corro­ sive nails are generally the most acceptable.

Be careful that copper nails are not used with Western Red Cedar, for the natural esters in this timber attack the copper.

Modern power-driven, self-drilling screws can be used and are recommended for use with fibrocement products, as they cut down the danger of cracking, which is greater if driven nails are used.

Turning corners, whether internal or exter­ nal, is the area that needs the most care when fixing weatherboards or planks. In natural timber, either a stop mould running vertically up the corner can be used, or the boards can be mitred. The latter is a skilled job and care must be taken to seal the end grain of the boards carefully, or there is always a risk that water will get into the joint and into the timber, causing fungal rotting.

Almost all cladding systems have special­ ly developed corner mouldings that simpli­ fy the process significantly.

Some of the profiled horizontal sheeting products in fibrocement-and to some extent in aluminium-will require vertical joints along long wall runs. Take care if the products are not used sympathetically, as these joints can look terrible.

Building paper is normally fixed to the outside of the timber frame before the sheets or boards are fixed; this is consid­ ered an integral part of most modern cladding systems. The building paper can be reflective to improve the thermal effi­ ciency of the house, or it can be brown kraft paper. It should always be fire-resist­ ant and it is recommended that the paper be perforated to allow air circulation and to reduce the tendency for condensation between the paper and the cladding.

Flashings for all windows and doors are important and the choice of the moulds used to finish cladding to opening junctions can have a major bearing on the final appearance of the house.

fixing strip cover strip

Hard1plank/weathertex Formed metal corner moulds external corners

FIBRE CEMENT JOINTING 124

DETAILS-WEATHER BOARD CORNERS

SHEET AND BOARD CLADDINGS • 39 COMMON SHEET CLADDING SYSTEMS Diagonal boarding Diagonal boarding is generally built using rebated softwood weather boards, other profiles and materials can be used. Wall sarking is recommended and 450mm maximum stud spacing.

Vertical boarding Vertical boarding is generally built using rebated boards or boards and battens. Wall sarking is recommended and multiple rows of noggings are essential (keep nail holes in straight lines).

Composite weather boards Composite weather boards are those manufactured from wood fibre (hardboard) or cement and fibre cement. These boards are normally used horizontally. Boards are available in smooth or textured surfaces.

- Jointing strip

Smooth finish

Textured finish

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II 11 Jointing 11 strip � I ii II II Ill

IX<'c�;.-----,1-Expanded metal Vers1lux or villaboard

Sheet JOlnt

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I Horizontal

Composite flat sheets Composite flat sheets are generally manufactured from cement and fibre cement. They can be used as finished cladding or they can be covered with expanded metal lathe and cement rendered.

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Profile moulded composite sheets Profile moulded composite sheets are generally manufactured from cement and fibre (asbestos cement). There are a number of profiles to choose from for vertical or horizontal application.

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Vertical

NB. Shingle must be twice as long as v1s1ble length

Shingles Wall shingles can be split or sawn hardwood or softwood or a manufactured material. Wall sarking is recommended or sub­ wall cladding in marine plywood. Battens are generally required over the studs to fix the shingles.

NB Shingle must be twice as long as visible length.

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40 • SHEET AND BOARD PRODUCTS Blue Board For many years the building industry had an unfulfilled demand for a long-life of coloured coating on a simple sheeting product. Any options were either compro­ mises or expensive.

In the 1950s, the Housing Commission in Victoria used two experimental building systems: one was a system of manufac­ tured reinforced concrete walls often referred to as the Holmesglen system, the other was known as conite.

The Holmesglen system of cast reinforced concrete panels, produced multicoloured houses of modest dimensions with a tradi­ tional plan and a conventional tile or corru­ gated iron roof. The system was also used to produced horrid high-rise flats, much like the Stalinist flats of the USSR. The conite system was simpler and allowed building of solid-looking houses with tiled roofs after WWII, when building materials were in short supply. Conite used a conventional timber stud frame covered with kraft building paper, wrapped with chicken wire, cement rendered and colour coated. It was a good system but it never found general acceptance-probably due to its Housing Commission associations.

From time to time, lightweight framed houq­ es have been sheeted with fibrocement

----Joist

sheets or marine plywoods, covered with chicken wire or expanded metal lathing, and then cement-rendered to produce any num­ ber of stuccoed finishes. This had little impact on mainstream home building until the condominium developments of Port Douglas and Sanctuary Cove: neo Mediterranean classicism in coloured renders.

Designers and builders began to experi­ ment with internal grade, recessed edge, fibrocement products with flush joints cov­ ered with thick, textured paint finishes.

Initially the results were poor: the joints cracked, the coatings slipped on the sheet surface, colours faded rapidly and the details used were often fussy.

Then modern fibrocement sheets were specifically developed for outside use under textured coatings. They form a com­ plete system, from the high bracing resist­ ance of the sheets themselves through the specially developed board sealers, jointing tapes and fillers, to the various textured coatings and protective coloured skins.

It is now possible to have a light timber or steel-framed house with a coloured tex­ tured stucco finish that allows greater mod­ elling of the building's exterior appearance than brick or weatherboard could ever achieve. Even better, the original paint should remain in good condition for over ten years and last more than 15 years. On

Texture coating

many of these coatings a repaint with a sin­ gle coat of exterior acrylic paint is all that will ever be needed every dozen or so years. If the coating is not kept spruce with repainting, it will simply become weathered and mellow with the passage of time.

A few points should be considered by those setting out to use this system for the first time: • Try to keep the sheet joints vertical, as horizontal joints are more likely to show.

• Make sure the base wall frame is flat.

• Take care that there are expansion joints in large wall lengths, particularly near external corners.

• In two-storey buildings a horizontal joint at the shrinkage/flexure line is required.

• Remember that most of the textured coatings are rolled on and some are trow­ elled over, so try to avoid vertical planes greater than. 3 metres high between rib­ bon projections.

• The details between the texture coating and windows, doors and other openings are areas of critical detail and need care­ ful design.

• It is much easier and quicker if the whole exterior of the building is scaffolded prior to the commencement of the sealing, jointing and finishing.

• The average house may need more than a tonne of coatings.

Timber or metal stud wall

Concrete slab ----

Detail of wall to base

126

Detail of wall to concrete slab

SHEET AND BOARD PRODUCTS • 40

Detail of head

BASE SHEET

TEXTURE COATING ARCHITECTURAL PROFILE SECTION BONDED AND SEALED ALL ROUND

FOAM SEALING STRIP, 10mm WIDE X Gmm THICK OR SEALANT Internal Corner

ALUMINIUM WINDOW FRAME

FLASHING (BY BUILDER)

)

Detail of sill

'\

TAPE AND JOINTING SYSTEM

BY COATING APPLICATOR

/

Straight Joint

ARCHITECTURAL PROFILE SECTION BONDED AND SEALED ALL ROUND

TAPE AND JOINTING SYSTEM

BY COAT! NG APPLICATOR 2 TO 3mm GAP

- TEXTURE COATING /REINFORCING TAPE

External Corner

BEFORE FIXING EXTERNAL I - CORNER ANGLE IN POSITION ANY GAPS BETWEEN 11 FILL BASE SHEETS WITH SEALANT

Detail of jamb

CRITICAL THESE EDGES ARE FLUSH

ARCHITECTURAL PROFILE SECTION FIXED TO TOP SHEET ONLY Flooring

"'

BOTTOM PLATE

I

TEXTURE COATING DO NOT NAIL BELOW CENTRELINE OF JOIST

I 0mm gap DO NOT BOND ARCHITECTURAL PROFILE SECTION BELOW SHEET JOINT SHEET MOVEMENT JOINT 2 STOREY CONSTRUCTION

/

- BASE SHEET NAILED TO TOP PLATE ALTERNATIVE MOVEMENT JOINT 2 STOREY CONSTRUCTION

127