A school roof renovation specifies an asphalt built-up roof, not a coal-tar system. Under 2021 IBC 1507.10.1, what is its minimum design slope for drainage?
- A1/8 inch per foot
- B1/16 inch per foot
- CZero slope
- 1/4 inch per foot
Where to look it up
https://core-docs.s3.amazonaws.com/documents/asset/uploaded_file/3836/Lennox/3042180/2021_International_Building_Code.pdf
Why D is correct
The built-up-roof minimum is 1/4 inch per foot. The 1/8-inch exception is for coal-tar roofs and does not apply here. Source: 2021 IBC 1507.10.1; https://core-docs.s3.amazonaws.com/documents/asset/uploaded_file/3836/Lennox/3042180/2021_International_Building_Code.pdf