DIY How to Change a Doorway Into a Window

Use a rubber mallet to knock out the hinge pins on the door from underneath then grab them with a pair of pliers at the top and pull them out the rest of the way from the hinges. Remove the door.

Detach the trim and door frame from the door opening. Remove the trim by wedging a pry bar between the wall and the trim then pushing against the pry bar. Repeat this at every nail location until the trim pulls away from the wall easily. Remove the door frame by placing the pry bar at a nail location in the frame, between the door frame and the edge of the stud. Lightly hammer the pry bar into place. Push against the pry bar gently to avoid breaking the door frame. Repeat for each nail in the frame until the frame sits away from the wall. Pull the door frame from the opening. Remove the exterior trim in the same fashion to access the door's two main studs.

Measure the door opening between the studs across its width. This is the width needed for the window. If the door opening is 36 inches, this will be an easy job as you can purchase off-the-shelf windows at any home improvement store in this size. If it is an uncommon width, the window will have to be special-ordered. Note that the height of the window must allow for at least 12 inches or more beneath the window for the sill and cripple stud supports.

Measure the height of the window. Transfer this measurement to each stud in the door opening. This is where you will place the bottom sill for the window. Then measure the width of the stud. If it is a 2-by-4 inch stud, purchase a 2-by-4 inch board the width of the door measurement. If it is a 2-by-6 inch stud, purchase the corresponding board.

Cut the sill board to fit the window's width with a skill saw. Line the top of the sill up with the bottom mark on the door's studs and toe-nail it into place with 3-inch galvanized framing nails, two on each end approximately 1/2-inch in from the ends of the board. Toe-nailing involves nailing at approximately a 45-degree angle through the sill into the stud frame. Repeat for the other side of the sill.

Use the skill saw to cut a board to fit across the bottom of the opening between the studs. Nail this into the floor. This is the bottom plate.

Use a tape measure to determine the distance from the top of the bottom plate to underneath the windowsill. Cut cripple studs to fit this measurement. These studs should be set 16 inches on center in the opening. Measure 16 inches from the opening's side stud, make a mark and measure from that mark 16 inches. Repeat across the opening.

Toe-nail two framing nails through the cripple studs to the bottom plate in the same manner as for the sill. Nail two framing nails through the sill into the cripple stud after ensuring the cripple stud is plumb. Use a level placed against the side of the cripple stud to check for plumb.

Install the window into the opening. Nail it into place from the outside with 1 1/2-inch nails along the bottom and sides of the window. Do not nail the top of the window to allow for contraction and expansion. If you nail the top of the window, it will be hard to open and close.

Place insulation between the cripple studs below the window.

Use masking tape to mark the location of the cripple studs on the floor. Measure and cut a piece of sheetrock into place across the bottom of the window, matching it up to the sheetrock on either side. Secure the sheetrock to the cripple studs with a power drill equipped with a Phillips head bit and screws. Place screws every 12 inches along the studs.

Measure and cut sheetrock to fit as needed then apply drywall tape on the sheetrock seams, centering the tape over each seam.

Apply joint compound over the drywall tape with a putty knife. Allow the compound to dry then sand the area with medium-grit sandpaper. Apply texture to the sheetrock, duplicating the pattern on the walls of the room. Sand again once it's dry. Add paint to match the room color.

Apply sheetrock trim around the inside of the window, installing it in the same manner as for underneath the window. Place tape where the corner of the window sheetrock trim meets the wall edge, placing the center line over the seam and folding each side down, one on the trim, one on the wall. Cover the tape with compound, let it dry then sand it. Paint or stain the trim, as desired.

Install a piece of oriented strand board over the area of the cripple studs on the exterior of the house. Add a waterproof vapor barrier by stapling it into place on the OSB board, then cut and fit a piece of external sheathing or siding to match the house's siding. Nail it into place following the same pattern used for the exterior of the house. Add trim to the exterior of the window to match the trim around the house's other windows.

Paint or stain the exterior sheathing or siding and trim to match the house's exterior and window treatment areas.