Roof Flashing Types

Overview of Roof Flashing Types

Roof flashing is not a single product. It is a category of shaped metal or synthetic pieces, each engineered for a specific roof joint or penetration. The main types are step flashing, drip edge, valley flashing, counter flashing, base flashing, kickout flashing, pipe boot flashing, and continuous (apron) flashing. Choosing the right type for each location is as important as the material itself. A drip edge cannot do the job of step flashing, and a pipe boot cannot replace a chimney flashing assembly. Understanding each type, where it goes, and how it fails is foundational knowledge for roofers, adjusters, and estimators.

Transition Flashing Types

Step flashing consists of individual L-shaped metal pieces, typically 4 by 4 inches, woven into each shingle course where a roof plane meets a vertical sidewall. Each piece overlaps the one below it by at least 2 inches, creating a stair-step water path down to the gutter. Roof-to-wall junctions also use continuous (apron) flashing for headwall transitions, where a single bent piece runs along the top of the wall-to-roof connection. Kickout flashing sits at the very bottom of a roof-to-wall intersection, angling water into the gutter instead of letting it run behind the siding. Building codes in many jurisdictions now require kickout flashing because wall moisture damage from its absence is so common.

Edge and Valley Flashing Types

Drip edge is an angled metal strip installed along the eave and rake edges of a roof. At the eave, it sits on top of the underlayment and extends past the fascia board by roughly 0.5 to 0.75 inches, directing water runoff into the gutter. Valley flashing lines the channel where two sloping roof planes meet. It can be an open metal valley (W-shaped or flat with a crimped center ridge) or a closed valley where shingles are woven or cut across the valley line over an underlayment of ice and water shield. Open metal valleys are more durable and easier to inspect, which is why many roofing manufacturers recommend them.

Penetration Flashing Types

Chimney flashing is typically a two-part system: base flashing (L-shaped pieces lapped up the chimney face) and counter flashing (metal embedded into the mortar joint that folds down over the base flashing). This two-layer approach allows the roof and chimney to expand and contract independently without breaking the water seal. Pipe boot flashing is a cone-shaped rubber or lead collar with a flat metal base that slips over vent pipes. The base is secured under the upslope shingles and over the downslope shingles. Skylight flashing is typically a pre-fabricated kit from the skylight manufacturer, incorporating step, head, and sill flashing pieces integrated into one assembly.