How to Fix a Basement Window

Remove the interior trim from the inside of the basement window you want to replace. Pry it off carefully with a pry bar so you can save it and use it later. Remove the exterior trim in the same manner. Slice away the old caulk with a utility knife.

Carefully remove the insulation that is packed around the window using a putty knife and needle-nose pliers. Save the insulation so you can use it with the new window.

Ask your helper to assist you in lifting out the old window. Clean away old mortar and debris from the window frame with the broom and putty knife.

Apply a line of caulk on the inside edge of the new window. Set the window inside the opening, and ask your assistant to hold it in place. Set a level against the new window to make sure it is sitting level. Place wooden shims under any low spots, and drive nails through the shims into the wooden window frame with the nail gun.

Put another layer of caulk around the outside of the window with the caulking gun. If there are any gaps between the window and the brick, spray some foam insulation in these spaces.

Put a bead of exterior caulk on the backside of the exterior trim you previously removed, and replace it around the window. Nail the trim to the wood frame with the nail gun.

Sink all exposed nail heads with the nail punch, placing the tip of the punch on the nail head and hitting it with the hammer. Apply wood putty to the nail holes with the putty knife. When dry, sand the putty smooth. Paint the trim with the exterior trim paint using the paintbrush.

Work on the inside of the window. Nail the wood shims to the wood window frame with the nail gun. Cut away any protruding pieces of wood shim with the utility knife.

Stuff the old insulation into the spaces between the wall and the window with the putty knife.

Install the interior trim on the inside of the window, just as you did with the exterior trim. Sink the nail heads with the nail punch as you did on the outside. Apply spackling to the nail heads on the trim with the putty knife. Sand the spackling with sandpaper, and paint the trim with interior paint and a paintbrush.