CSLB C-39 Roofing ContractorSteep-Slope RoofingHard
A roofing inspector is examining a newly installed slate roof. The slates are 24 inches long, and the roof slope is 8:12. To conform to best practices and code, what should be the exposure of these slates?
- A10.5 inches
- B10 inches
- C8 inches
- D9 inches
Show answer & explanationAnswer & explanation
Correct answer: A. 10.5 inches
The formula for calculating slate exposure (E) is (L - H) / 2, where L is the length of the slate and H is the headlap. For a typical 8:12 slope and 24-inch slate, a 3-inch headlap is standard. Therefore, the exposure is (24 - 3) / 2 = 21 / 2 = 10.5 inches.
Why the other options are wrong
- B. 10 inches exposure would result in a headlap of 4 inches (24 - 2*10 = 4), a common and good practice, but not the exact calculation for a 3-inch headlap.
- C. 8 inches exposure would result in an excessive headlap of 8 inches (24 - 2*8 = 8), which is unnecessary and inefficient.
- D. 9 inches exposure would result in a headlap of 6 inches (24 - 2*9 = 6), which is more than typically required.
Slate Exposure Calculation
Slate exposure is calculated by subtracting the headlap from the slate's length and dividing by two.
- E = (L - H) / 2.
- Headlap often 3 inches.
- Determines roof aesthetics and water shedding.
Memory trick: Length minus headlap, then split in half, for slate's true path.