Some parts of roofs and exterior walls are particularly prone to leaks and water damage. These include roof valleys, the intersection between a dormer wall and the roof surface, and chimney and skylight perimeters—nearly anywhere runoff is heavy or where two different opposing surfaces meet. These areas require the extra protection that flashing provides.

You can find flashing made of plastic, roofing felt, and rubber, but your best bet is rust-resistant metal, either galvanized steel, aluminum, or copper. Most flashing is made of galvanized sheet metal.

Aluminum flashing is made for use with aluminum siding and roofing materials and, because it is easy to bend, for do-it-yourself installation.

Copper flashing is custom fabricated for use with copper roofs and some specialty applications.

Continuous flashing protects the joint between a vertical wall and a sloped roof.

Vent-pipe flashings fit over flues and pipes that protrude through the roof. Made of sheet metal, they’re cone-shaped with a flange at the base; this flange is worked into the shingles as roofing is applied.

Z-flashing seals the horizontal seams between plywood or hardboard siding panels.

Valley flashing protects the valleys between two meeting roof planes. On most roofs, this W-shaped channel is placed on top of building felt before the finished roof is installed.

Drip caps are L- or Z-shaped metal flashings that flash frames above windows and doors.

Drip edges prevent water from seeping under roofing along the edges of rakes and eaves. They’re applied under roofing felt along eaves and over roofing felt along rakes.

Step flashing is a type of flashing that steps up a roof to protect where the roof meets side walls of chimneys, dormers, and some skylights. It actually consists of a series of right-angled metal pieces; each section is worked into a course of shingles so that it overlaps the section beneath it.
The flashing’s vertical edge is usually tucked under siding or capped with a second counter flashing that is mortared into the chimney or caulked along a skylight so water can’t sneak in behind it.

Chimney flashing is applied around the base of a chimney in several parts: continuous flashing along the bottom, step flashing up the sides, and saddle flashing at the top. Cap flashing, mortared or caulked into the chimney, laps over the top edges of the other flashings to prevent water from running behind them.

Skylights often have their own integral flashing. Otherwise, their curbs are flashed with continuous flashing along the base, step flashing up the sides, and saddle flashing across the top.

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