Flanged & Proud Window

This window detail uses a two stage seal to insure no water or air can infiltrate into the building. The exterior seal is installed by applying WRB tape over the head window flange. No tape should be applied over the sill window flange to allow the window to drain. The interior seal is added by installing a full perimeter backer rod & sealant joint. Expanding foam or special tapes can be used instead of sealant, however a backer rod should still be installed to prevent the foam from completely filling up the cavity and preventing the system to drain. Plastic shims should be used to level out the window in the rough opening. These shims elevate the window slightly, which creates a space for water the drain.

To create a continuous air barrier, the pre-assembled plywood extension box needs to be sealed to the wall's fully adhered air barrier and the window with sealant joints.

* Whether or not you need a Class II or III Vapor Barrier depends on your climate zone, location and amount of exterior insulation. Refer to Wall Barriers Notes section below for more info.