CSLB C-39 Roofing ContractorSteep-Slope RoofingHard
A contractor is installing a new 24-inch wood shake roof on a building with a 7:12 slope. The shakes are being installed with a single-course application. What is the maximum allowable exposure for these 24-inch wood shakes to ensure adequate weather protection and compliance with industry standards?
- A7.5 inches
- B10 inches
- C9.5 inches
- D8.5 inches
Show answer & explanationAnswer & explanation
Correct answer: B. 10 inches
For 24-inch wood shakes installed in a single-course application on a pitch of 7:12, the maximum allowable exposure is typically 10 inches. This provides a triple-layer coverage over the entire roof surface, as (24 - 10) / 2 = 7 inches of headlap, which is sufficient for a 7:12 slope.
Why the other options are wrong
- A. 7.5 inches is too conservative for a 7:12 slope and 24-inch shakes, commonly used for double-course applications.
- C. 9.5 inches is close but not the typical maximum for 24-inch shakes on a 7:12 slope in a single-course application.
- D. 8.5 inches is less than the maximum allowable and would provide more overlap than strictly necessary for this slope.
Wood Shake Exposure
Exposure for wood shakes is the portion of the shake that is left exposed to the weather after installation, determined by shake length, application method, and roof slope.
- Exposure affects the number of layers of coverage on the roof.
- Single-course applications typically have greater exposure than double-course.
- Steeper slopes allow for greater exposure due to better water shedding.
Memory trick: Shake's stretch: steep the pitch, wider the reach.