Residential Building Inspector B1Roof-Ceiling ConstructionMedium
An inspector observes a newly installed asphalt shingle roof with a pitch of 3:12. What is the minimum headlap required for the asphalt shingles on this roof according to the IRC?
- A2 inches
- B5 inches
- C3 inches
- D4 inches
Show answer & explanationAnswer & explanation
Correct answer: C. 3 inches
For asphalt shingles installed on a roof with a pitch less than 4:12 but not less than 2:12, the minimum headlap required is 3 inches. This is specified in IRC Table R905.2.8.1(1) or R905.2.8.2.
Why the other options are wrong
- A. 2 inches is typically not sufficient headlap for asphalt shingles on any standard roof pitch.
- B. 5 inches is not a standard minimum headlap requirement for asphalt shingles.
- D. 4 inches is the minimum headlap for roof pitches 4:12 or greater.
Asphalt Shingle Headlap
The shortest distance from the lower edge of an overlapping shingle to the upper edge of the shingle in the second course below it, providing weather protection.
- Increases with shallower roof pitches.
- Critical for preventing water penetration.
- Measured vertically between courses.
Memory trick: Pitch dictates overlap; shallower means more headlap to stop leaks.