Installing a Wood Window

Cut strips of roofing felt or building wrap and cover the bottom of the rough opening. Later (steps 7-9) you will install additional wrapping and/or flashing.

Set the window temporarily in place, check for level, and shim the bottom as needed. If your window calls for installing a thick flashing with a piece of plywood at the bottom install it first or raise the window by the same thickness.

Tap in shims at the sides, checking for plumb as you go. Don't wedge the shims too tightly, or the jambs will warp. Use the level as a straightedge to confirm that the jamb has not warped.

Make sure the window operates smoothly with the shims in place. Watch the alignment of the sash against the jambs as you move it. Adjust the shims as needed.

Tack (partially drive) nails or screws near the shims to hold the window temporarily in place.

On the outside, trace around the brick molding to mark the siding for cutting. Cut the siding.

Pry back the siding and install the felt, building wrap, or self-adhesive flashing. Cut pieces of felt or self-adhesive flashing to fit along the sides. Slip them in behind the siding, fold them over the studs, and staple. Cut a piece 6 inches longer than the width of the opening and install it the same way. Cut slits at the corners.

The slits cut on all four corners create V-shaped openings in the felt or flashing. Cover these with small pieces of felt or self-stick flashing.

If your window calls for it, use tin snips to cut a piece of metal drip cap flashing and slip it under the felt at the header.

Set the window back in place, with the brick molding tight against the felt or flashing. Inside, the front of the jambs should be flush with the finished wall. (Where you have not yet installed new drywall, the jambs should be 1/2 inch proud of the framing.)

Again shim the bottom and sides, check for level and square, and check that the window operates smoothly. Following manufacturer's directions (you may need to remove pieces of trim first), partially drive 6d finishing nails through the jambs to attach the window.

Outside, drive galvanized casing nails to attach the brick molding. Caulk between the trim and the window and between the trim and the siding.

Use a nail set to drive the finishing nails slightly below the surface of the wood. Where these nails are not covered with trim, apply wood putty to the resulting holes.

Use a handsaw to cut the shims flush with the studs, so you can install the drywall up against the jambs.

Gently stuff fiberglass insulation into the gaps around the jambs or fill the gaps with nonexpanding spray foam insulation. Expanding foam could warp the window frame.