In this video, This Old House general contractor Tom Silva explains how to install a waterproof window.
Steps on How to Waterproof Your Window:
- Staple 15-pound builder's felt along bottom of window opening.
- Apply adhesive-backed waterproof membrane over the felt; cut the corners and fold the excess membrane over the rough sill.
- Cut small pieces of waterproof membrane and cover voids in corners of opening.
- Apply a wide strip of waterproof membrane to each side of the opening; run the flashing past the header and overlap the bottom flashing.
- Set the window in the opening.
- From inside, slip shims under the window.
- Center window in the opening, then check the bottom of the window for level.
- Drive a single nail through the nailing flange on the window's high side.
- Raise the low side of the window to level, then nail through the flange.
- Check vertical edge of the window for plumb; shim if necessary.
- Measure the opposing diagonals of the window to ensure that it's square.
- Finish nailing the window to the wall.
- Apply a wide strip of waterproof membrane across the top of the window.