Construction Tech - Flash Cards - L2
Flat roof, Lavant - Why did you specify a warm deck roof?
The existing roof was a warm deck, it is economically and practically advantageous to keep to a warm deck.
Flat roof, Lavant - What are the benefits of a warm deck roof?
Good thermal performance, no requirement for ventilation preventing the risk of condensation build up.
Flat roof, Lavant - What is the differences between a warm deck, cold deck and inverted roof?
Warm deck - insulation above the deck.
Cold deck - insulation between the rafters with ventilation.
Inverted - Insulation on top of the waterproof covering. (pro: waterpprofing is protectcted form mechanical / UV damage. Con: Themal briging can be a concern)
Flat roof, Lavant - Why did the existing insulation level need to be increased?
To meet the Building regulations U-value requirement within part L (0.18 w/m2k).
Flat roof, Lavant - What are the Part L requirements for flat, pitched roofs and roof lights?
Vol 2 table 4.1:
Flat roofs - 0.18
Pitched Roofs - 0.16
Rooflights - 2.2
Windows 1.6
Flat roof, Lavant - What did you need to consider in relation to the flashings of the first floor windows?
That the windows would require replacement, reduction in size to ensure that the 150mm upstand requirement is achieved.
Flat roof, Lavant - Why is a 150mm upstand required? Where is this standard from?
Protects the covering and surrounding construction. Detailed in BS 6229 (Flat roofs).
Flat roof, Lavant - What did you specify to ensure that the flashing requirements were met?
Ensure a minimum of 150mm upstand was provided in accordance with BS 6229.
Flat roof, Lavant - What type of flat roof replacement was installed and why?
Bauder 2 layer RMB warm roof. Existing was warm deck, tapered system required due to insufficient falls, client requirements (design guide / guarantee).
Flat roof, Lavant - How was the existing build up of the warm deck roof constructed?
Timber deck, bitumen vapour control, cork insulation, flet covering.
Flat roof, Lavant - What was specified for the roof replacement?
Bauder 2 layer warm deck, strip existing waterproofing / cork, retain existing VCL, apply primer to VCL, apply VCL, insulation, underlayer and capping sheet.
Flat roof, Lavant - Why was Bauder the chosen option?
Manufacture undertook survey and specification inc conjunction with client requirements, allowed for tapered insulation. Allowed for Safe2Torch application.
Flat roof, Lavant - What is Safe2Torch?
National federation of roofing contractors campaign to reduce the fire risk in installation using gas torches.
Flat roof, Lavant - How much insulation was required? What is the U value?
The manufacture undertook a thermal analysis to confirm that an average of 130mm would achieve the 0.18w/m2K u-value as required in Part L (vol 2).
Flat roof, Lavant - What regulation is adhered to for creating flat roof falls?
BS6229:2018, all flat roofs should be designed with a fall of 1:40 to ensure a finished drainage fall of 1:80 is achieved as required by the building regulations.
Flat roof, Lavant - What Approved documents did you need to refer to for this project?
Part A - Structure, For consideration of additional loading.
Part B (vol 2) - Fire, Resisting fire spread over roof coverings.
Part C - Site preparation and resistance to contaminants and moisture.
Part H - Drainage & waste disposal, Drainage of rainfall to the flat roof.
Part K - Protection from falling, collision & impact, Fall protection (if required)
Part L - Conservation of fuel and power, U-values