Installing a Nail-Fin Window Over a Fluid-Applied WRB
As we add thicker insulation and more water-sensitive materials to the walls of our houses, it becomes increasingly important to detail our exterior walls to keep water out. Window flashing is one of the parts of a house where this matters most. Getting flashing details right for the common nail-fin-style window means making leakproof transitions between the water-resistive barrier (WRB) and the flanges that fasten the window to the wall.
In this Fine Homebuilding Shop Class video series, professional builder Jake Bruton demonstrates the crucial steps for getting the flashing details right when installing a flanged window in a wall with a fluid-applied WRB, where the entire wall is covered in a liquid sealant to keep air and moisture out. In the first episode, Jake prepares the opening in the wall by applying sealant onto the edges of the rough opening and the entire surface of the studs inside the opening before troweling it to create a flat, continuous moisture barrier. Next, he adds a bead of the same sealant around the sides and top of the opening before inserting, plumbing, squaring up, and fastening the window in place. The third episode outlines the methods for masking the window frame with painter’s tape and then covering the top and side window flanges with the liquid sealant to create the primary flashing details. Finally, he applies foam and quality caulk in the gaps between the window and the interior side of the rough opening to wrap up this airtight, energy-efficient installation.