Framing a patio door means building the wooden structure that holds the door unit in place
A patio door frame is the rough opening — the hole in your wall where the door will sit. You build it with studs, a header, and a sill, then set the door unit inside and seal it. The frame has to be square, level, and the right size for your door, or the door will stick, leak, or not close properly. Most patio doors are 36 inches wide and 80 inches tall, but always check your door's specifications before you cut anything.
The work breaks into three parts: removing the old wall if one exists, building the frame itself, and installing the door unit. If you are replacing a door that is already there, you will remove the old frame first. If you are opening a new wall, you will cut through the drywall, insulation, and exterior sheathing to create the opening. Either way, the frame goes in before the door.
Key Takeaways
- Measure your patio door unit before you frame anything — the rough opening should be 1 to 1.5 inches wider and taller than the door itself to leave room for shimming and sealing.
- A header (a beam above the opening) must be sized for the weight it carries; a 36-inch opening usually needs a doubled 2x8 or 2x10 depending on what is above it.
- The frame must be square and level or the door will bind and leak — use a level and a framing square at every step.
- Patio doors are heavy and need solid support at the bottom; the sill must be properly sloped and sealed to shed water away from the house.
- After the frame is built, the door unit sits inside with shims under the sides and header, then is nailed or screwed through the flanges into the frame.
Measure the door and plan the rough opening
Before you cut into the wall, you need to know exactly how much space the door needs. Check the manufacturer's instructions for your specific door unit — they will list the rough opening width and height. Most patio doors need a rough opening that is 1 to 1.5 inches wider and 1 to 1.5 inches taller than the door itself. This gap is for shims, which are thin wedges you use to level and square the door after it goes in.
Mark the opening on the wall with a pencil. Use a level to draw vertical lines on both sides and a horizontal line at the top and bottom. If you are replacing an existing door, remove the old frame and door first. If you are opening a new wall, you will need to cut through drywall on the inside and exterior sheathing on the outside. Check for studs, electrical wiring, and plumbing before you cut — use a stud finder and look inside the wall if you can.
Measure the height from the floor to where the header (the beam above the opening) will sit. Most patio doors are 80 inches tall, so the rough opening is usually 81.5 inches. The header sits on top of the studs on either side of the opening, so the studs below it need to be cut to the right height.
Remove the existing wall section if needed
If you are replacing a door, remove the old frame and door unit first. Pry out the door with a flat bar, then remove the nails or screws holding the frame to the studs. Once the frame is out, you may need to remove studs that are in the way of the new opening. Use a reciprocating saw to cut studs in the middle, then pry them out. Leave the studs on either side of the opening — these become the king studs that support the header.
If you are opening a new wall, cut through the drywall with a drywall saw, then cut through the insulation and exterior sheathing with a reciprocating saw. Work carefully around any studs, wiring, or pipes. Once the opening is clear, you can see the studs and plan where the new frame will go.
Build the frame with studs, a header, and a sill
The frame consists of four main parts: two king studs on the sides, a header across the top, and a sill at the bottom. The king studs are the full-height studs that support the header. The header is a beam (usually two 2x8s or 2x10s nailed together) that spans the opening and carries the weight of the wall above. The sill is the bottom piece that the door sits on.
Start by installing the king studs. These are full-length studs that run from the floor to the top plate of the wall. They sit on either side of the opening. If studs are already there, use them. If not, cut new studs to length and nail them in place with 16-penny nails, three nails per connection. Use a level to make sure they are plumb (perfectly vertical).
Next, build the header. A header for a 36-inch opening usually needs to be two 2x8s or two 2x10s nailed together, depending on the load above. Check local building codes or ask at a building supply store — the size depends on how much weight the header has to carry. Nail the two boards together with 16-penny nails in a staggered pattern, then lift the header onto the king studs. Nail it down with 16-penny nails, at least three per side.
Install the sill at the bottom. The sill is usually a 2x6 or 2x8 that runs across the bottom of the opening. It must be level and sloped slightly toward the outside so water runs away from the house. Nail it to the floor framing with 16-penny nails. Use a level to check that it slopes about 1/4 inch per foot toward the outside.
Check that the frame is square and level before installing the door
Before you set the door in the frame, the frame itself must be square and level. Use a 4-foot level on the sill to make sure it is level side to side. Use a level on the king studs to make sure they are plumb. Measure diagonally from corner to corner inside the opening — if both diagonal measurements are the same, the opening is square. If they differ by more than 1/4 inch, adjust the frame by moving the king studs slightly until the diagonals match.
Shim behind the king studs if needed to make them plumb. Shims are thin wedges of wood. Drive them in behind the studs, then nail the studs to the wall framing through the shims. Check with a level after each shim to make sure the stud is plumb.
Set the door unit in the frame and find it
Once the frame is square and level, set the door unit in the opening. Most patio doors have a nailing flange — a strip of material around the edge that you nail or screw to the frame. Lift the door carefully and set it on the sill. It should sit flat without rocking.
Shim under the sill and up the sides of the door to level and square it. Start at the bottom corners and work your way up. Use a level on the door itself to check that it is level side to side and plumb front to back. The door should open and close smoothly without binding. Once the door is level and square, nail or screw through the flanges into the frame. Use the fasteners specified in the door's instructions — usually 1.5-inch nails or screws spaced 16 inches apart.
Seal the gap between the frame and the wall with caulk or expanding foam. This keeps air and water out. Once the caulk or foam is dry, you can install trim on the inside and outside to cover the gap and finish the installation.
Seal and insulate around the door frame
After the door is fastened in place, seal all the gaps between the frame and the wall. Use expanding foam on the sides and top, and caulk on the sill. Expanding foam fills large gaps and provides insulation. Caulk is better for the sill because it is flexible and sheds water. explore foam first, let it cure, then trim the excess with a utility knife. explore caulk over the foam and smooth it with a wet finger.
On the outside, seal the gap between the door frame and the exterior sheathing with caulk or foam as well. This is critical — water will find any gap and cause rot. Some doors come with a flashing kit that goes under the sill and up the sides to shed water. If yours does, install it before you caulk.
Frequently Asked Questions
What size header do I need for a patio door opening?
A 36-inch opening usually needs a doubled 2x8 or 2x10, depending on the load above. A single-story wall with a roof above typically needs a 2x10. Check your local building code or ask at a building supply store — the size depends on the span and the weight it carries.
Can I frame a patio door in an existing wall without removing studs?
Only if the studs are already positioned where you need them. If studs are in the way, you have to remove them and build a header to carry the load they were carrying. Never remove a stud without replacing its load with a header.
How much space should I leave between the door frame and the rough opening?
Leave 1 to 1.5 inches on all sides. This gap is for shims, which let you level and square the door. Too little space and you cannot shim; too much and you waste caulk and foam.
What happens if the frame is not level or square?
The door will bind, stick, or not close properly. Water will also leak in at the gaps. Always check with a level and measure diagonals before you install the door. It takes a few extra minutes and saves hours of trouble later.
Do I need a flashing kit for the sill?
Yes, or at least caulk the sill thoroughly. Water runs down the exterior and collects at the sill. A flashing kit or heavy caulk job directs that water away from the house. Without it, water will seep into the wall and cause rot.