What Is Roof Flashing?
Flashing is thin metal (galvanized steel, aluminum, or copper) installed wherever water must be redirected: roof-to-wall joints, chimneys, valleys, skylights, and pipe penetrations. Step flashing is installed piece-by-piece with each shingle course, overlapping the course below; counter flashing embeds in masonry and covers the step flashing above it. Most roof leaks originate at flashing details rather than in the shingle field, which is why chimneys, valleys, and pipe boots are the first places an inspector or insurance adjuster looks. Neoprene pipe-boot gaskets commonly fail in 10-15 years under Texas UV - often long before the shingles - and reusing old flashing during a replacement is a classic corner-cutting defect. Flashing condition frequently decides whether storm damage is repairable or whether a leak is excluded as wear-and-tear on an insurance claim.
Important Distinction
Note: Flashing is not caulk: sealant is a maintenance material with a service life measured in years, while properly lapped metal flashing sheds water mechanically for the life of the roof. A transition that depends on a bead of sealant to stay dry is a scheduled future leak, not a finished detail.
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Also Known As
These are the search terms and phrases that commonly refer to this topic, so you can find it however you describe it.
How Roof Flashing Relates to Other Topics
Failed or deteriorated flashing is one of the most common sources of roof leaks and is typically corrected through a targeted roof repair rather than a full replacement.
Most roof leaks start at flashing - the joints where the roof meets a wall, chimney, or pipe - not in the open field of shingles, so a leak hunt starts at the nearest penetration uphill of the stain.
Flashing is integrated into the shingle courses during installation rather than added afterward, because sealant-only flashing is a common failure origin.
Related To Roof Flashing
Skylight flashing kits apply the general flashing principle — shed water by overlapping geometry, never rely on sealant — to one specific roof penetration.
Roof-mount fan bases are a flashing detail: self-flashing models integrate the flashing base for low-profile roofs, while curb-mount models use a curb and flashing kit on tile, metal, and flat roofs.
Apron flashing at the downhill face of a chimney or dormer laps OVER the shingles below it, while flashing above laps under - reverse the lap and the roof is built to leak on day one.
Skylights leak at their flashing kit, rarely through the glass - and reusing an old skylight's flashing on a new roof pairs a 30-year surface with the one part already proven to be at end of life.
In the layered roof system, flashing is the exception layer - it handles every place the field layers get interrupted by a wall, chimney, or pipe, which is why flashing quality predicts leak history better than shingle brand does.
Questions about Roof Flashing?
Zilker Roofing inspects before recommending. Honest assessment, no pressure.