Roofs Flashcards
What requirements might you consider when designing a roof?
Ventilation
Insulation
Structural integrity
Resistance to moisture
Wind loading
What are key considerations when designing flat roofs?
Dead and imposed loads
Prevention of water penetration
Heat retention but also interstitial condensation
What is a cold roof?
A roof where the insulation on the underside of the structural deck.
What is a warm roof?
A roof where the insulation is on top of the structural deck, sandwiched between the vapour control layer and waterproof covering.
What is an inverted roof?
A roof where the insulation sits on top of both the structural deck and waterproof covering and it typically held down by ballast.
What is the typically frequency of wall straps?
2M centres
When is a vapour control layer required?
Where no ventilation is allowed within the roof then a VCL is needed.
What is the purpose of a vapour control layer?
To prevent warm damp meeting the dew point in the roof and causing interstitial condensation.
Under part L, what U-value does a falt roof need to reach as a minimum?
0.18
What are different types of flat roof covering you might specify?
Asphalt
GRP
Built up felt
Single ply such as EPDM
Lead
Zink
Why might your specify Asphalt and what are some of the disadvantages?
Cost-effective and has a 25 year life expectancy
Heat applied in bays and then covered in a layer of UV paint
Pros: seamless
Cons: prone to embrittlement and slumping at upstands.
Why might your specify GRP and what are some of the disadvantages?
Cold applied and can therefore be installed without hot works permits. It is suitable for use an an overlay system.
Pros: jointless and lightweight
Cons: weather dependent install and relatively costly.
Why might your specify a felt system and what are some of the disadvantages?
layers of felt laid a right angles with cap sheet for UV protection - 25 year life expectancy
Typically torched on
Pros: straightforward installation
Cons: trapped moisture can result in blistering requiring careful detailing.
Why might your specify a single ply system and what are some of the disadvantages?
EPDM - life expectancy of 25 years
Pros: lightweight
Cons: due to complex detailing required it is more likely to fail due to poor workmanship. The detailing can also therefore be time consuming.
What solar protection options are there for flat roof systems?
stone chippings
paving slabs
solar reflective paint
