Ice & water shield (also called self-adhered membrane) is best known for snow climates—but it can be extremely useful in California when installed in the right locations.
In the Bay Area, the biggest benefits come from protecting details exposed to wind-driven rain and concentrated water flow.
What ice & water shield actually does
- Seals around fasteners to reduce leak paths
- Provides a waterproof layer under shingles in high-risk zones
- Helps prevent blow-back leaks where water is pushed upward by wind
Where it’s commonly worth using in California
Valleys
Valleys carry the most water. A membrane under the valley detail adds critical redundancy.
Skylights and roof penetrations
Membrane around skylights, pipes, and transitions adds protection if flashing gets stressed or debris backs up water.
Eaves and edges (especially with gutters)
At eaves, water can back up during heavy storms or when gutters overflow. Membrane helps protect the edge detail and decking.
Low-slope transitions
Where a steep roof meets a low-slope section, membrane can help manage water that slows down and spreads.
Where it can be overkill
- Full-coverage membrane on a steep, well-ventilated roof with low leak risk
- Applications that trap moisture if ventilation and air sealing are poor
Membrane is not a substitute for correct ventilation and detailing.
Installation details that matter
- Deck must be clean and dry before application
- Correct overlaps and tie-ins at valleys and penetrations
- Compatible products that match the roofing system warranty
- No “fishmouths” or wrinkles that create water channels
Next step
If you’re planning a reroof or you have recurring leaks at valleys, skylights, or edges, ask about membrane placement as part of the system detail—not as a random add-on. For help, start with roof repair or request an inspection.