CSLB C-39 Roofing ContractorSteep-Slope RoofingEasy
A roofing contractor is preparing to install asphalt shingles on a roof with a 5:12 slope. What is the minimum recommended headlap for standard three-tab asphalt shingles on this roof?
- A4 inches
- B1 inch
- C3 inches
- D2 inches
Show answer & explanationAnswer & explanation
Correct answer: D. 2 inches
For standard asphalt shingles on slopes 4:12 and greater, the minimum headlap required is 2 inches. This ensures proper water shedding and prevents leaks.
Why the other options are wrong
- A. 4 inches of headlap is excessive for a 5:12 slope and would significantly reduce the exposure of the shingles.
- B. 1 inch headlap is insufficient for proper water shedding on a 5:12 slope.
- C. 3 inches of headlap is often used for lower slopes (e.g., 2:12 to less than 4:12) or in high-wind areas, but not strictly required for a 5:12 slope.
Asphalt Shingle Headlap
Headlap is the shortest distance from the butt edge of an overlapping shingle to the top edge of the shingle in the second course below it.
- Crucial for water shedding.
- Varies with roof slope.
- Ensures watertightness.
Memory trick: Headlap's 'H' keeps the 'H'2O out.