CSLB C-39 Roofing ContractorSteep-Slope RoofingMedium
A roofing contractor is preparing to install a new open metal valley on an asphalt shingle roof. To ensure adequate water flow and prevent debris accumulation, what is the minimum recommended width for the metal valley at its narrowest point (e.g., at the top of the valley)?
- A6 inches
- B10 inches
- C4 inches
- D8 inches
Show answer & explanationAnswer & explanation
Correct answer: A. 6 inches
For an open metal valley on an asphalt shingle roof, the minimum recommended width at the narrowest point (top) is typically 6 inches. This width allows for proper water flow and minimizes the risk of debris buildup, ensuring effective drainage.
Why the other options are wrong
- B. 10 inches is a very wide valley, often used for large roof areas or low slopes, but not a minimum requirement at the narrowest point.
- C. 4 inches is generally too narrow for an open valley, increasing the risk of water overflow and debris clogging.
- D. 8 inches is a common width for valleys, especially as they widen towards the eaves, but 6 inches is the minimum at the top.
Open Metal Valley Width
The horizontal distance between the edges of the roofing material where it meets the metal flashing in an open valley.
- Crucial for effective water drainage.
- Varies with roof slope and design.
- Minimum width prevents clogging and overflow.
Memory trick: Six inches wide, for water to glide.