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Alex Dibble /

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Arc 401

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Student Name: Alex Dibble

Student Number : Q10807098

Faculty: Maritime and Technology Level of study: Undergraduate Course title: Architectural Technology Unit title: Principles of Construction Technology Assignment title: Arc 401 Assignment 1314 Assignment tutor: Verity Bird Word count: Learner request for feedback:

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Alex Dibble /

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Arc 401

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Arc 401

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Arc 401

Arc 401 Assignment Question D. As the ground conditions described at the start of the question are firm clay then it could still be susceptible to volume change potential, so you would still have to account for minor volume change when the ground swells and shrinks. However unlike soft clays, when a piled foundation would need to be used as the ground cannot support a trench filled foundation. However because it is a firm clay type then the ground can support the much easier and cheaper trench fill method of foundations. This is possible because firstly the trench for the foundations can be dug out without the sides falling in and secondly the clay is firm enough to hold the buildings weight without moving around. (Bird, 2013C, slide 19) But to account for the minor swelling in the clay due to seasonal weather I would still use a suspended block and beam concrete floor, as the void underneath it will allow for any minor change in the ground. Whereas a ground bearing concrete slab may be able to do the job but in harsh winters or long summers the amount of ground change could become too great and either break through the floor or leave a gap under the floor big enough to weaken the structure and eventually fall in on itself. As stiff clays are still subject to seasonal volume change the strip foundations have to be lowered to a depth of at least 0.9m, to a point where the clay is not affected by the seasonal change. Although the clay at the base of the structure will not be subject to the movement of the clay the section at ground level will be, this is why you would fill the gap in the cavity wall with a 50mm thick compressible material to prevent lateral movement. (Emmitt and Gorse, 2010, p54) As I am using a beam and block suspended floor to support a rear wall and I do not know the type of floor in use and I would have loads from the floors and roof then the load category for the structure would be a load C according to the Good Building guide. And as I am building on Firm clay my minimum foundation width would be 450mm. And as the thickness of the foundation cannot be less than the amount that the foundation projects from the wall with a minimum requirement of 150mm. So as a normal cavity wall is about 325mm wide then 450-328=122mm so the thickness would have to be a minimum of 150mm deep. (BRE Good Building Guide)

Question E. A ‘Cold Roof’ is a roof structure where the insulation is laid just above the ceiling, leaving the entire roof void above un-insulated. (Bird, 2013, slide 4) This means that in its current state the roof space would be uninhabitable as there would be no way of heating the entire roof void.

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Arc 401

The insulation in a cold roof is usually Rockwool or another type of quilt insulation that is laid directly on top of the ceiling, between the roof joists and along the top of the ceiling joists so that it complies with modern building regulations. (Bird, 2013, slides 5,8) The main problem with a cold roof is that the likelihood of condensation inside the roof space is very high, and if it were to occur it would be on the ceiling as that is the part of the build where the cold air would meet the warm air. This would weaken the structure of the roof if water was allowed to sit on the ceiling and slowly seep through. To help prevent the build up of condensation and any vapour build up in the roof the roof space would be very well cross ventilated, so that any water that accessed the roof would simply be caught in the cross ventilation flow and be carried out of the other side of the roof. And as the roof void is already cold then the problem of heat loss due to ventilation is very minimal, the only problem being that as the roof void would become so cold over the winter you would have to incorporate a method of frost protection on any pipes or tanks that were installed up in the roof space. (Bird, 2013, slide 11)

The simplest way to make the roof space habitable and useable as accommodation would be to change it from a cold roof to a warm roof construction. As you can see the main difference between a warm roof and a cold roof is the positioning of the insulation, where a cold roof create a seal around the first 2 floors by having the insulation above the ceiling a warm roof has the insulation placed on the outside of the rafters and in between the rafters to create a full thermal seal around the entirety of the body of the structure to allow the roof space to be at the same temperature as the rest of the house. (Bird, 2013, slide 4) Another main difference between cold and warm roofing is the use of board insulation such as Kingspan or Celotex which must be cut to shape and fitted snugly into all the gaps between rafters to ensure no gaps are left that may become a cold bridge in the building. A cold bridge is a spot in the buildings inner leaf that has no insulation where cold air can get in and warm air can escape. These are usually found at the eaves, as it is very difficult to ensure that the cavity is completely filled with insulation, at balcony structures, as they have to go a certain depth into the wall to ensure that it is safe and at an opening in a wall for windows and doors and such as they cannot be insulated so you have to ensure that whatever is fitted into that gap had a good airtight seal on it. (Bird, 2013, slide 8) And if there are cold spots in very warm buildings then the risk of condensation is very high.

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And the ventilation in a warm roof is also different as you cannot simply cross ventilate through the roof space as that would let all of the heat out, so some systems use a 50mm ventilation gap to allow the vapour out but the main systems are a breathable membrane to allow vapour to escape but not enter and to reduce the risk of interstitial condensation vapour barriers are used. (Bird, 2013, slide 12)

Question F. Part E of the Building Regulations stipulates that all “dwelling-houses, flats and rooms designed for residential purposes must be constructed in such a way that they provide reasonable resistance to sound from other parts of the same building or adjoining buildings�. (NBS,2010) As such you cannot simply use a boarded timber floor with rigid plasterboard ceilings, as they do not prevent the transmission of sound well at all. So there are certain construction methods used to help reduce the transmission of sounds. (Emmitt and Gorse, 2010, p125) The wall construction that i will be using will be Type 4 on Part E of the Building Regulations, otherwise known as framed walls and timber floating floors with absorbent materials. A. With the framed walls construction that I have chosen, and as you can see in the drawing the floor is made from 2 separate sections, meaning that there are no slid sections through the wall that will allow sound to travel through them, there is instead a completely hollow void where the sound will have to travel through. This will greatly reduce Impact sounds caused by people moving around and moving objects around in their house or flat, but will not do much to prevent airborne sound. (Bird, 2013B, slide 9) To help prevent airborne sound transmission through the floor a material is added into the void to help dissipate the sound vibrations, this material is normally mineral wool, which is draped between the rafters as you can see in the picture. (Emmitt and Gorse, 2010, p126) The mineral wool acts as an absorbent layer for the sound waves to help reduce them greatly. The other option to be used that could be used as well as or instead of the mineral wool would be pugging, a method whereby you place a layer of sand or plaster on top of the bottom section of the floor, as you can see in the picture. This, like the mineral wool or carpet acts as an absorbent layer for the sound waves, to help greatly reduce the amount of sound that can get to the next floor. (Emmitt and Gorse, 2010, p126)

B. The main reason that the junction between a first floor and an external wall cannot be simple is because of the problem of Page 6 of 6


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flanking sound transmission. As sound travels in waves and is formed by vibrations it can easily escape and travel around corners so you need to take extra precaution and work in extra construction detail to prevent this. The main way to do this as you can see in the picture is to use a cavity stop, which is a cavity barrier made from insulation that can simply be fit into the gaps to create a barrier to help prevent the sound waves from passing through

C.

One of the main problems for a timber floating floor when it meets an interior wall is preventing the sound from simply reverberating through the wall and getting into the room on the other side of the wall. To overcome this problem is simple, as you can see from the picture you simply leave another void between the wall and the next room, this void will help to dissipate the sound. Any pipes in this void will need to be coated in mineral wool insulation to prevent them from simply carrying the sound vibrations around the building.

Question G. As the structure is for industrial use, and I will be using it as a warehouse/workshop, I will make it from a simple steel frame with a truss and gurder roof, as they are simple to erect and can span widths of up to 12m. (Bird, 2013D, slide 3) But first, the foundations that the construction will sit on will be raft foundations, as they allow the load of the structure to be spread evenly across the ground. As the ground conditions are still variable and the only option for industrial flooring is a ground bearing slab then allowing for the problem of minor ground movement changes would have to be addressed by the foundations. This is why I have used a raft foundation, as it will allow the ground to shrink and expand whilst still spreading the weight evenly so that there is not one specific point that is under particular strain, if one point in the ground changes shrinks a noticeable amount then the raft foundation allows that load to be spread over the rest of the foundation, instead of pushing that point to fail. (Emmitt and Gorse, 2010, p61)

The floor build up was an easy decision, as the only possible option for an industrial building is ground bearing slab. This is very similar to the ground bearing slab used in domestic housing, but because it is on such a large scale there are just a couple of differences. The first of which being that there is no screed on an industrial ground bearing slab although there might be a Page 7 of 6

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Alex Dibble /

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Arc 401

hard wearing top on it depending on its use. As my unit will be used as a workshop then it will have a hard wearing stop on it as it will contain a lot of heavy machinery and will have a lot of things being moved around inside, so a hard wearing top will be needed to keep the floor safe as any holes that may cause people to trip over would be a health and safety hazard. (Bird, 2013E, slide 7) The other main difference is that the insulation is never laid on top of the concrete, making the slab much better protected as in a normal house it would be laid on top of the concrete and below the layer of screed. But as there is no screed then there cannot be any insulation above the concrete. And if the floor is large enough then you can simply only insulate the edges of the floor to complete the continuity and link it up with the insulation in the walls. This can be done by laying the insulation horizontally under the edge of the slab or vertically. (Bird, 2013E, slide 8) The last part of the build up will be the cladding, which is laid on the secondary structure of the steel framed industrial unit. The Primary structure is used to transfer the loads of the build down into the foundations and into the ground and then the secondary structure is designed onto the primary structure as a means of fixing the outer cladding to the structure. The secondary structure on a simple steel framed industrial unit is made up of small, light steel sections as they only need to carry the load of the cladding. (Bird, 2013D, slide 7 and 8) As you can see from the drawing I decided to use low level masonry to improve the aesthetics of the structure and help increase its lifespan. Masonry at low levels helps to strengthen the building by giving it a very sturdy base and it can take low level impact well without any visible problems, whereas profiled sheeting will dent. It is also much better for fire resistance which is key at the low levels where the workers would be working. And the cladding that I have decided to use on this build is composite panels, which have all 3 key parts of the cladding, the lining tray the insulation and the profiled sheeting, constructed together and delivered to site in one sheet. This means that they are much easier to install as they can simply be delivered to site and fixed onto the z section purlins from the secondary structure. This also greatly reduces any human error in the cladding as there is just the one section to fit on as opposed to the 3 independent layers of the sandwich construction. It also comes with a vapour barrier built into it, to help reduce the risk of condensation. (Bird, 2013D, slides 31-33)

Bibliography Bird V, 2013; CTS Roof Tut 2 accessed at http://mycourse.solent.ac.uk/course/view.php?id=7091, 06/12/2013 Bird V, 2013B; CTS Floors Tut Acoustics 12 accessed at http://mycourse.solent.ac.uk/course/view.php?id=7091, 07/12/2013 Bird V, 2013C; CTS Founds 1 Spread founds 12 accessed at http://mycourse.solent.ac.uk/course/view.php?id=7091, 07/12/2013 Bird V, 2013D; CTS Walls 3 Ind systems 1213 accessed at http://mycourse.solent.ac.uk/course/view.php?id=7091, 10/12/2013 Bird V, 2013E; CTS Floors 3 Ind floors accessed at http://mycourse.solent.ac.uk/course/view.php? id=7091, 10/12/2013

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BRE Good Building Guide, accessed at http://mycourse.solent.ac.uk/course/view.php?id=7091, 10/12/2013 Building Regulations Part E 2010; NBS; accessed at http://www.planningportal.gov.uk/uploads/br/BR_PDF_AD_E_2010.pdf, 07/12/2013 Emmitt S and Gorse C, 2010; Barry’s Introduction to Construction of Buildings; Wiley-Blackwell

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