A roofer is installing a new slate roof. The slate tiles are 18 inches long, and the roof has a 6:12 slope. Per good roofing practice and building codes, what is the minimum required headlap for these slate tiles?
- A2 inches
- B3 inches
- C4 inches
- D5 inches
Show answer & explanationAnswer & explanation
Correct answer: B. 3 inches
For most slate roofing installations, the minimum headlap is 3 inches. However, for longer slates (over 16 inches) or steeper slopes, a 4-inch headlap is often preferred for added security. Given the 18-inch slate and 6:12 slope, 3 inches is the absolute minimum, but 4 inches would be better practice. Since the question asks for MINIMUM, 3 inches is the correct answer. The formula for exposure (E) is (L - H) / 2, where L is the length of the slate and H is the headlap. With an 18-inch slate and a 3-inch headlap, the exposure would be (18 - 3) / 2 = 7.5 inches.
Why the other options are wrong
- A. 2 inches of headlap is generally insufficient for slate, especially for 18-inch tiles, and would not meet code for typical slopes.
- C. 4 inches is a commonly recommended headlap for slate, especially for longer tiles or steeper slopes, but 3 inches is the minimum.
- D. 5 inches of headlap would significantly reduce the exposure and aesthetic appeal of the slate without a proportional increase in protection for this slope.
Slate Headlap
The headlap for slate roofing is the distance an overlapping slate extends over the top of the second slate below it.
- Crucial for water shedding and wind resistance.
- Typically 3 inches minimum, but can be more.
- Influences slate exposure and roof aesthetics.
Memory trick: Slate's minimum headlap, a triple shield against the drip.