CSLB C-39 Roofing ContractorSteep-Slope RoofingMedium
A roofing contractor is installing a new asphalt shingle roof on a residential property. The roof has a 6:12 slope. According to standard practice, what is the minimum required headlap for these asphalt shingles?
- A2 inches
- B4 inches
- C1 inch
- D3 inches
Show answer & explanationAnswer & explanation
Correct answer: A. 2 inches
For asphalt shingles on roofs with slopes from 4:12 to 21:12, the minimum required headlap is 2 inches. This ensures proper water shedding and prevents leaks.
Why the other options are wrong
- B. 4 inches headlap is excessive for a 6:12 slope and not a standard minimum requirement for asphalt shingles.
- C. 1 inch headlap is insufficient for asphalt shingles on a 6:12 slope, risking leaks.
- D. 3 inches headlap is typically used for lower slopes (2:12 to 4:12) or specific shingle types, not standard for 6:12.
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 course immediately below it. It is crucial for preventing water penetration.
- Ensures proper water shedding.
- Varies based on roof slope and shingle type.
- Measured vertically on the shingle.
Memory trick: Headlap: How much shingle 'head' is covered, keeping water from 'lapping' under.