CSLB C-39 Roofing ContractorFlashing, Ventilation and InsulationMedium
A crew is fabricating open valley metal flashing for a composition shingle roof in an area requiring corrosion-resistant sheet metal per code. What is the minimum acceptable gauge for galvanized steel valley flashing under standard California building code provisions?
- A16 gauge
- B32 gauge
- C26 gauge
- D20 gauge
Show answer & explanationAnswer & explanation
Correct answer: C. 26 gauge
Building code tables for open valley flashing specify a minimum of 26 gauge corrosion-resistant sheet metal (such as galvanized steel) to provide adequate durability and water-shedding performance without being excessively heavy or costly.
Why the other options are wrong
- A. 16 gauge is far thicker than required and not the code-referenced minimum for this application.
- B. 32 gauge is thinner than code allows and would be inadequate.
- D. 20 gauge exceeds the standard minimum specified for valley flashing.
Valley Flashing Minimum Gauge
Open valley flashing using galvanized steel must meet a minimum thickness of 26 gauge per standard code provisions to ensure adequate corrosion resistance and durability.
- Minimum 26 gauge galvanized steel for valley flashing
- Applies to open valley composition shingle installations
- Thinner gauges fail to meet code durability standards
Memory trick: Twenty-six is the valley's magic number for steel.