How to Convert a Window into a Door

beautiful backyard is only as good as the access to it. That’s the challenge a couple faced when they reached out to the Ask This Old House team. Their home had a lovely fenced-in backyard, but the only access was through the front of the house and a garden gate.

Carpenter Nathan Gilbert knew exactly how to help. He spotted a double window on the back of the house that was perfect for conversion into a door. With the homeowners’ assistance, Nathan removed the old windows, wall paneling, and framing to make way for a new sliding patio door. Here’s how the conversion process went.

Steps to Convert a Window Into a Door

1. Choose the Right Window
   Select a window (or windows) wide enough for an entry door, patio door, or French door. Check for any outlets beneath the window that might need relocating.
2. Remove the Window
   Use a utility knife to score the paint around the window stops. Pry off the stops with a pry bar and hammer. Then, remove the screws holding the window in place and pull the window out.
3. Remove the Trim and Paneling
   Score the paint where the window trim meets the wall and remove the trim with a pry bar. Do the same for any paneling or wainscoting below the window.
4. Remove the Window Frame (if applicable)
   For homes with replacement windows, cut the original window frame with a reciprocating saw and pry it out.
5. Check for a Header
   Ensure a header exists in the opening to support the load. If not, build one by cutting two 2x12s to the width of the opening, gluing them together, and securing with nails and screws.
6. Install Jack Studs
   Add jack studs beneath the header to support the weight. For balloon-framed homes, the jack studs should sit on the foundation. In platform-framed homes, the studs will rest on the bottom plate.
7. Repair Fire Blocking (Balloon Framed Homes)
   If removing the studs left a gap in fire blocking, install short studs and a 1×6 board to fill the gap. This acts as the new bottom plate.
8. Seal the Opening
   Cut a piece of rubberized membrane slightly wider than the opening. Adhere it carefully around the edges, ensuring it sticks firmly. Seal the corners with silicone caulk.
9. Install the Door
   Lift the door into the opening, placing the bottom in first. Use shims to ensure it’s snug and level. Secure the door with screws through the predrilled holes.
10. Apply Flashing
    Apply rubberized flashing around the door’s exterior to seal any gaps. Start with the sides and finish with the top, overlapping the flashing at the edges.
11. Seal the Interior
    Fill the gap around the inside of the door with expanding foam. Finish with new casing on the interior and install J-channel casing on the exterior before patching the siding.

And just like that, you’ve successfully transformed a window into a functional door!