How to Turn a Window Into a Door

What good is a beautiful backyard if you don’t have a way to get into it? That’s what a pair of homeowners faced when they called the Ask This Old House team for help. Their beautiful home has a fenced-in backyard, but to gain access, the couple’s children would have to walk out the front of the home and through a garden gate.

Carpenter Nathan Gilbert Knew just how to help. He located a double window on the backside of the house that would be perfect for converting to a door. With the couple’s help, Nathan removed the old windows, wall paneling, and even some framing to make way so he could install a new sliding patio door. Here’s how he did it.

Steps To Convert a Window to a Door

The following steps will explain how to convert a window to a door. However, it’s important to choose the correct window for the project. Look for a window (or set of windows) that is wide enough to accommodate an entry door, patio door, or French door. Also, take note if there are any outlets underneath the window, as you’ll need to move them if there are. In most cases, a double window off of a dining room is a great choice.

1. Start by scoring the paint around the window stops with a utility knife, and then pry them off the window with a pry bar and hammer.
2. Remove the four screws holding the window into the opening. There should be two on either side of the window, a few inches from the corners. Pull the window out from the opening. If it’s difficult to remove, remove the window sashes first and then pull the frame out of the window.
3. Score the paint where the window trim meets the wall. Remove the trim with a pry bar and hammer, being careful not to damage the wall during the removal. Repeat the process if there is any paneling or wainscoting below the window, as well.
4. If you had replacement windows, the original window frames will still be installed in the window opening. Remove them by cutting each of the original jambs about halfway up with the reciprocating saw, and then prying them out with the pry bar.
5. Ensure that there is a header in the opening. If your home is platform framed, there will likely be a header stretching from one side of the opening to the other. If your home is balloon framed, you may only have standard 2x6s installed on the flat to create the top plate of the rough opening. In either case, you’ll need to ensure there is a header that can carry the load. Note: All exterior walls are load-bearing, so you may need to build a temporary support wall inside the home if a structural header is not present.
6. Remove any studs from the opening with the reciprocating saw, including the smaller studs and plates at the bottom of the window opening. Once cut, use a sledgehammer to knock them out of the home to remove them. Also, if you don’t have a structural header at the top of the opening, cut the plates at the top of the rough opening and remove them.
7. Build a header by cutting two 2x12s to the width of the rough opening and gluing them together with construction adhesive. Nail and screw the boards together.
8. Lift the header into the rough opening and screw it into place with a few toe-nailed screws. Then, install jack studs underneath the header. If the home is balloon framed, the jack studs should be long enough to sit on the foundation while also holding up the header. If the home is platform framed, the jack studs will sit on the bottom plate. In both scenarios, the studs must sit on the structure below to disburse the weight from above the door.
9. If the home is ballon framed, removing the studs will likely have left a hole where the old fire blocking (small lengths of 2×6 installed between the studs at the floor level) between the floors. Repair this gap by first installing two short studs on either side of the opening, cut to the same height as the original studs (¾-inch below floor level). Then, cut and install a 1×6 board over the gap securing it to the studs below with nails or screws. This board will act as the new bottom plate.
10. Cut a piece of rubberized membrane to be roughly 8 inches wider than the opening. Starting approximately 4 inches up from the bottom plate at the side of the opening, remove the backing slowly and lightly adhere the membrane in place. Once all of the back is removed, press down firmly and rub the membrane so that it adheres permanently.
11. Squeeze a bead of silicone caulk along each corner and along the interior side of the membrane to create a dam of sealant that the door can sit in and seal out water.
12. Carefully lift and place the door into the opening, bottom first. Use wood shims around the opening to snug it into the opening, and use the level to check for plumb. Adjust as necessary and secure the door by driving screws through the predrilled holes and into the framing behind. Cut the shims flush with the multi-tool.
13. Apply rubberized flashing on the outside of the door. Start with the sides of the doors, bridging the gap between the framing and the door jamb. Once both sides are covered, flash the top of the opening with the membrane, overlapping the flashing on either side of the door.
14. Apply expanding foam designed for windows and doors in the gap around the inside of the door. Finish the interior of the door with new casing, and install J-channel casing around the outside of the door before patching the siding.

Resources

To remove the windows, Nathan starts by scoring the paint around the window stops with a utility knife. Then he uses a pry bar and hammer to pull off the window stops.

After removing the stops, remove the window sashes and the frame. Score along the paint line of the window trim with a utility knife. Use a pry bar and hammer to remove the window trim and the wall paneling under the window.

To remove the jamb, use a combination of prying tools and a reciprocating saw.

Self-adhesive flashing tape provides an added layer of protection to the rough opening. Create a water-resistant seal by putting a layer of silicone sealant along the edge of the flashing tape.

After fitting the door in place, support, and level the door with shims. After checking that the door is level use screws to secure it. Add flashing tape around the exterior border of the door with a ¼” overhang. Add Self-adhesive flashing tape to the exterior header.

If you have questions about your DIY door and window projects, speak with a The Home Depot associate through the Home Depot’s Millwork Virtual Apron program for expert help and advice.

Products and Services provided by F.D. Sterritt Lumber Company and MP Doors.

Materials

• 2×6 lumber
• 2×8 lumber
• 1×6 lumber (for balloon-framed homes)
• Rubber membrane
• Silicone caulk
• New patio door
• Wood shims
• Wood screws
• Rubber flashing tape
• J-channel

Tools