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FLAT ROOF
Robert 17/12/2025 - 11.46 AM
I have put planning in for a flat roof. However the height is only 2.8m height max from the outside floor. 150mm to DBC then floor to ceiling height is 2350 so only leaves me with 300mm left. The flat roof is going to be 8.3m long x 5.9 wide. Please can someone tell me what height it needs to be please. Will 3m total height be enough so say 500mm for a flat roof.
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3 Answers
LEBELLE HERITAGE & RESTORATION LTD
Rating: 5 out of 5
With a maximum external height of 2.8m and a 2350mm internal ceiling height, this leaves around 450mm for both the floor build-up and roof structure, which is very tight. A flat roof on a span of 8.3m x 5.9m will typically require more depth once joists, insulation, and falls are allowed for. Increasing the overall height to around 3.0m would be more practical and should allow a compliant flat roof build-up of around 500mm, subject to structural design and Building Control approval.
Answered17 December 2025
1
Anonymous user
A total building height of 3m, providing 500mm for the roof assembly, is a more suitable and achievable height. Due to the large span, you will need detailed structural calculations from a qualified engineer to confirm the exact specifications of the joists or beams (likely engineered timber or steel).
We hope this helps!
Answered17 December 2025
1
Edenbridge Property
Rating: 5 out of 5
Very tight as Warm Roof spec is now so high to meet Building Regs. It would need to be surveyed but guessing at 8" x 2" rafters with 180-200mm celotex above + choice of roof covering.
Answered17 December 2025
1