Commercial Building Inspector B2Building EnclosureHard
A commercial building inspector is reviewing the installation of a new roof covering on a low-slope roof with a slope of 1/4:12 (2%). The specification calls for a built-up roof (BUR) system. Which of the following is the minimum number of plies of roofing felt required for this type of roof covering?
- AFive plies
- BFour plies
- CTwo plies
- DThree plies
Show answer & explanationAnswer & explanation
Correct answer: D. Three plies
IBC Section 1507.5.3, for built-up roofs on slopes 1/4:12 (2%) or greater, requires a minimum of three plies of felt. This ensures adequate waterproofing and durability for low-slope applications.
Why the other options are wrong
- A. Five plies is excessive and not the minimum code requirement for this application.
- B. Four plies would provide greater protection but is not the minimum required.
- C. Two plies are insufficient for a typical built-up roof system on a low slope.
Built-Up Roof (BUR) Ply Count
The minimum number of layers of roofing felt and asphalt/bitumen required in a built-up roof system for waterproofing.
- Minimum of three plies for slopes 1/4:12 or greater.
- Each ply adds to the waterproofing and durability.
- Specific requirements vary based on felt type and asphalt/bitumen.
Memory trick: Three plies make a strong BUR, for a low-slope roof, that's for sure.