Folding Corner Flashing for a Seaside Dormer

Folded metal and construction tape team up for a bulletproof dormer flashing job in a tough exposure.

Multiple Planes

The dormer, shown here after flashing is applied, intersects two roof planes (a steeper roof at the dormer sides, and a lower-slope porch roof at the dormer front). The two roof planes also intersect in front of the dormer, adding to the geometric complexity.

Lapping Over

Pollard starts down-slope from the dormer's front wall, bending a piece of flashing to lap from the lower-slope roof in front of the dormer, up the short rake section and lapping onto the top of the steeper roof.

Pinning the Piece

Pollard pins the lowest flashing piece with a stainless steel nail (here, working on the left side of the dormer).

Inside Corner

Here, Pollard makes a piece of flashing for the inside corner where the dormer's front wall meets the side rake of the steeper upper roof. He folds a piece of flashing, cuts across one side, and then folds again to make a half cube, then tapes the seam from the back side.

Taped Corner Piece

A view of the underside and back of the inside corner flashing, with its seam sealed from the back with tape, ready to place.

Inside Corner Flashing

The front inside corner flashing piece, ready to install.

Placing an Inside Corner

Pollard sets the inside corner flashing in place. The window sill has already been protected with Grace Ice and Water Shield bitumen-backed plastic membrane.

Pinning the Corner Piece

Pollard pins the corner flashing piece to the roof with a stainless steel nail.

Roof Head Flashing

This long piece of flashing will extend across the front of the dormer where the dormer front wall meets the lower roof. It laps over the corner piece that has just been placed, and will ultimately be overlapped again by Henry membrane placed in the window sill. Here, Pollard cuts the flashing to fold down onto the window sill.

Folding Onto the Sill

Pollard bends the flashing down over the rough window sill with taps from a hammer.

Pinning the Flashing

Pollard pins the flashing to the window sill with a few stainless steel nails, over a previously applied bead of silicone caulking.

A Tape Seal

For a water-tight joint, Pollard applies Zip tape to the steeper roof edge, lapping down over the previously placed corner flashing.

Taped Roof Edge

Another view of the taped and flashed roof-to-rake transition.

Taping Flashing to the Wall

Pollard applies Zip tape to the top edge of the dormer front flashing, waterproofing the joint between the upper wall and the flashing. This location will also later be covered by Henry Blueskin.

Roof to Front Corner

Pollard begins constructing a two-piece flashing for the dormer's front corner roof intersection by crimping a bend in what will be the front edge of the lower flashing piece, resting on the roof.

Making a Cut

With the top of the flashing piece toward him, Pollard cuts down to the bend in the flashing piece. The part to his left will lie flat on the upper roof; the part to his right will lie against the front face of the dormer.

Cheek and Face Cut

Here, Pollard makes cuts on the flashing piece that will lie on the roof and fold up onto the dormer cheek, and bend around to the dormer face.

Cheek and Face Bend

Here, Pollard has bent the second piece for the two-piece flashing. The part toward Pollard will lie on the steep roof. The white part facing the camera will lie against the dormer cheek, and the short section away from Pollard will lie against the dormer face.

Fitting the Pieces in Place

Pollard slides the two flashing pieces into place around the dormer corner.

Joining the Pieces

With the two flashing pieces set in place, Pollard tapes them together to hold their position relative to each other.

Sealing From the Back

Now, Pollard pulls the two flashing pieces off the dormer and tapes the joints between them from the back side with Zip tape.

Taping the Seams

Pollard tapes a two-piece flashing from the back.

Taping the Seams

Another view of Pollard taping the seams on the back of the two-piece flashing.

Completed Piece

The two-piece flashing, sealed with tape, lying ready to install.

Ready to Install

A view of the two-piece flashing from the back, sealed with tape.

In Position

A view of the flashing in place (before sliding it under the shingles), showing how it fits against the dormer.


The flashing installed beneath the shingle, pinned in place with a nail through the front face. This location will later be covered, first with adhesively attached Henry Blueskin housewrap, then with preservative-treated corner trim.

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