A qualified roofing contractor will be able to advise on this but here are some of the main guidelines.
Minimum flat roof pitch building regulations.
Built up roofs require a minimum roof pitch of 1 4 12 or greater.
Wood shingles require a minimum roof pitch of 3 12 or greater.
The below drawing shows the u value requirements set out for new properties in the building regulations for each element walls floors and roofs.
Pitch roof this is where tiles or slates are used and a void is usually created underneath.
Roof slope equivalents as rise.
When installing or repairing a flat roof you must adhere to building regulations.
Flat roof this usually consists of felting which has a slight fall to allow rain water to drain off.
Roof pitch multiplier table.
Notes to table 9 26 3 1.
With regards to the pitch the building standard code bs 5534 recommends a minimum pitch of 20 0 for slate roofs.
But since there is still a wide variety of slate roofing systems there are occasions when the minimum pitch can go down to as low as 15 0 depending on the uniqueness of the roof.
Building codes and roofs.
Part h of the building regulations regarding drainage state that water should drain to one or two edges.
There must be a slope of 1 80.
Complete list of roofing types.
3 profiled metal roof cladding systems specifically designed for low slope applications are.
It is a requirement of building regulation part h that adequate provision is made for rainwater to be carried from the roof of the building.
According to bs 6229 bs 8217 flat roofs should be designed with minimum falls of 1 40 to ensure a finished fall of 1 80 can be achieved allowing for any inaccuracies in the construction.
This is the basis for calculating the angle which is approximately a 1 19 degree slope.
A correctly build flat roof will drain the rainwater quickly and effectively into the gutters without allowing water to collect in depressions and pond on the surface of the roof leading to the build up of silt deposits on the roof and stresses in the membrane when the water freezes a small amount of ponding is inevitable and it should not reduce the.
To enable compliance with the requirements of the building regulations to be demonstrated full details of the new roof will be needed including.
1 see sentence 9 26 3 1 2.
Flat roof drainage.
Mineral surfaced roll roofing requires a minimum roof pitch of 1 12 or greater.
2 see sentence 9 26 3 1 3.
Slate and slate type shingles require a minimum roof pitch of 4 12 or greater.
According to the international building code the typical built up flat roof that uses tar or asphalt goes by the guideline that for every foot 12 inches of a flat roof a minimum of inch must step up or down.
The actual specification required for a compliant building and necessary building fabric u value targets may vary depending on the actual overall proposed specification and the outcome of the energy.
Run in degrees and as percentage the minimum roof slope allowed by code for any type of roof is in 12 applicable only to coal tar pitch roof systems.
