Protecting the Sill

Redundant waterproof layers create airtight and watertight protection for the windowsill.

Ice and Water Shield

Mark Pollard and Tyler Stroud apply Grace Ice and Water Shield to the rough windowsill, lapping the sticking membrane onto the top course of roof shingles on the roof below the dormer, to protect the framing from the driving rain of ocean storms.

Attention to Corners

At the intersection of the sill and jack, Pollard applies cut pieces of ZIP flashing to seal corners.

Sill Flashing

Pollard applies a custom-bent piece of aluminum coil flashing to the window opening base. The flashing extends down the dormer face and onto the roofing shingles below.

Sloping the Sill

Stroud sets shingles onto the prepared opening to create a drainage slope under the window unit. He lays the shingles into a bead of silicone caulking for a better water and air seal.

Fastening the Shingles

Stroud fastens the shingles to the sill with stainless steel staples.

Priming the Shingles

Before applying Henry Blueskin WB25 window flashing to the shingles, Pollard primes the wood with Henry Spray Prep primer as recommended in the manufacturer's literature.

Applying Sill Membrane

Stroud (left) and Pollard apply the WB25 membrane to the sill. WB25 is vapor-closed, waterproof, and airtight.

Applying Sill Membrane

Pollard fits and smooths the WB25 membrane onto the sill, lapping down onto the site-bent aluminum flashing. WB25 is a peel-and-stick product, but Pollard has observed that it only adheres well when the company's recommended primer is sprayed on before the sticky membrane is placed.

"Bow Tie" Corner Piece

At corners, Pollard applies a carefully cut piece over the small gap.

"Bow Tie" Corner Piece

Pollard places a corner patch over the small gap in the membrane at the window rough opening corner. Note: when multiple layers of Henry WB25 sill flashing are lapped in this fashion, Henry primer should be sprayed onto the lower piece and allowed to dry before the upper patch piece is placed.

Rolling the Membrane

For a good adhesive bond, it's important to apply pressure to the WB25 window flashing with a rubber roller, as shown here.

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