Butyl Window Flashing Installation

Measure the width of the window opening in the wall.

Measure a piece of butyl window flashing to the width of the window -- plus an additional amount equal to twice the width of the flashing tape. For example, if the window opening is 2 feet wide and the tape is 3 inches wide, the length of tape needed is 2 feet 6 inches. Cut the tape with utility shears.

Peel back a couple inches of the backing paper from one end of the strip.

Center the flashing lengthwise across the bottom of the window opening, and widthwise across the seam between the house wrap or foam-board insulation and the window opening.

Press the sticky side of the flashing against the wall, beginning at one side of the window and working across to the opposite side. Peel off the backing as you work across the flashing tape to gradually expose adhesive.

Install the window, following the manufacturer’s instructions.

Measure the height of the window. Cut two strips of flashing to that length plus twice the width of the tape.

Peel off a small amount of backing paper from one end of a cut strip.

Center the flashing lengthwise along the height of the window, and widthwise along the seam between the window and the house wrap or foam-board insulation. Press the tape in place, and repeat on the opposite side of the window.

Cut a strip to fit across the top of the window plus twice the width of the tape, and press it into place.