CSLB C-39 Roofing ContractorSteep-Slope RoofingEasy
A roofing contractor is installing a new asphalt shingle roof on a residential property. The roof has a 6:12 slope. To ensure proper drainage and weather resistance, what is the minimum required headlap for standard asphalt shingles?
- A3 inches
- B4 inches
- C2 inches
- D1 inch
Show answer & explanationAnswer & explanation
Correct answer: C. 2 inches
For standard asphalt shingles on slopes 4:12 and greater, the minimum required headlap is 2 inches. This ensures that water is shed effectively over the underlying shingle.
Why the other options are wrong
- A. 3 inches of headlap is often used for lower slopes (e.g., 2:12 to 4:12) or specific shingle types, but is not the minimum for 6:12.
- B. 4 inches of headlap is excessive for a 6:12 slope and would reduce the shingle exposure unnecessarily.
- D. 1 inch headlap is typically insufficient for standard asphalt shingles on a 6:12 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.
- Ensures water sheds over the underlying shingle.
- Varies by roof slope and shingle type.
- Critical for weather resistance.
Memory trick: Headlap's height keeps the roof just right.