CSLB C-39 Roofing ContractorSteep-Slope RoofingHard
A roofer is installing an open metal valley on an asphalt shingle roof. Per standard practice, what should be done regarding the shingles adjacent to the valley?
- AShingles should be nailed directly through the center of the valley metal for maximum hold
- BShingles should be installed with a 1-inch gap on only one side of the valley
- CShingles should be trimmed to expose a clear metal channel, with edges clipped and sealed with roofing cement
- DShingles should overlap completely across the valley with no exposed metal visible
Show answer & explanationAnswer & explanation
Correct answer: C. Shingles should be trimmed to expose a clear metal channel, with edges clipped and sealed with roofing cement
In an open valley, shingles on both sides are trimmed back to expose a clear metal channel (typically widening from about 3 inches at the ridge to wider at the eave), with the upper corner of each shingle clipped and embedded in roofing cement to direct water flow without trapping debris.
Why the other options are wrong
- A. Nailing through the valley metal center penetrates the water channel and causes leaks.
- B. A one-sided gap does not meet open valley standards and would cause water intrusion.
- D. Full overlap with no exposed metal describes a closed-cut valley, not an open valley.
Open Valley Flashing
A valley design where metal flashing is exposed and shingles are trimmed back on both sides to create a clear water channel.
- Metal channel widens toward the eave
- Shingle corners clipped and sealed with cement
- No nails placed within the exposed metal area
Memory trick: Open channel, no nails in the middle.