How to Apply Flashing to Brick When Installing Vinyl Window

Measure the window opening's width at the top and bottom edges. Transfer both of these measurements to 1-by-4 boards. Cut the boards to length with a miter saw.

Lay the 1-by-4 meant for the bottom edge in place. Center the board over the window opening's bottom edge. Drill 1/8-inch pilot holes using a hammer drill and masonry bit, spaced approximately 12 to 14 inches apart, through the board and into the brick. Drive 3-inch masonry screws through each pilot hole. Repeat this step with the 1-by-4 meant for the window opening's top edge.

Measure the distance between the top and bottom 1-by-4 boards on the window opening's right and left side. Transfer these measurements to two new 1-by-4 boards. Cut the boards with a miter saw.

Push the boards into place; it should be a tight fit. If necessary, lay a scrap board over the 1-by-4 and hit it with a hammer to fit the board tightly into place. Secure both side boards to the brick wall the same way you secured the top and bottom boards.

Apply a bead of masonry sealant along the seams where the 1-by-4 boards meet the brick wall.

Dip a paintbrush into liquid flashing. Paint the flashing over the 1-by-4 boards as well as along the surrounding brick. Use a back and forth motion to apply the flashing. Extend the liquid flashing about 8 inches up both of the window opening's sides.

Wait two to three hours for the initial application to be dry to the touch. Apply a second coat of the liquid flashing the same way you applied the first coat. Wait 24 hours for the liquid flashing to cure before you install the window.