Roofing
Flashing
Sheet metal (typically aluminum, galvanized steel, or copper) installed at roof transitions, penetrations, and joints to prevent water from entering the building.
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In the Field
Most roof leaks occur at flashing failures, not shingle failure. Step flashing at walls, chimney flashing, pipe boot flashings, and valley metal are the most critical details. Never use roofing caulk as a substitute for proper flashing — it will fail within a few years.
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Rule of Thumb
Step flashing at walls should be one piece per shingle course — not a single bent piece running the length of the wall. Interlocked step flashing sheds water; a continuous piece traps it.