How to Replace the Glass in Sliding Patio Doors

An open, sliding glass patio door with a screen where a dog looks out.
  • 3-6 hours
  • Intermediate
  • 500-1,200
What You'll Need
Putty knife
Pry bar
Tape measure
Straight edge
Glass cutter

Sliding patio doors offer good access to the outdoors and a wonderful source of natural light indoors. However, the location means that a stray ball or stone can easily break the glass, and if damaged, it needs to be replaced quickly. You can call a glazier, but it’s significantly cheaper to do the job yourself. It’s not as big of a project as you might imagine! It can actually be completed in a couple of hours, including all the clean up.

Step 1 - Trim

Replacing the glass on sliding patio doors doesn’t mean removing the entire door; it can be done with the door in place. The first thing you need to do is remove the trim around the glass, which is known as the mull. Slide a putty knife in between the trim and the door and then use a small pry bar and hammer to ease it off. Be careful not to bend or damage the trim as you work, and wear gloves and long-sleeved clothes to protect your hands during the job since broken glass is obviously a hazard.

Step 2 - Removing Glass

With those pieces gone, you can remove the remnants of the glass. Pick out as much as you can. There will inevitably be some pieces that remain stuck to the frame, so use the putty knife to remove these before you take off the caulk around the trim.

Step 3 - New Glass

You will need to use a tape measure to calculate the size of replacement glass for your doors. Measure both the height and width of the opening and then remove about a quarter of an inch from each measurement to obtain the size to buy. Any glass shop will be able to cut a panel to the size you specify. If possible, have them deliver the glass too, as it won’t fit in a car and they will know how best to pack it to protect it from damage.

Step 4 - Fitting the Glass

Inspect the glass after it arrives. If the edges aren’t completely straight you’ll need to trim them. Use a straight edge and gently scribe where needed with a glass cutter. Don’t try to make deep cuts, as these can break the new glass. Finally, check the measurements and the edges one more time to be certain that everything is straight and that the glass will fit the opening.

Put a bead of caulk around the inside of the frame. Gently ease the glass into place and then put another thin bead of caulk on top of the glass. This will hold it against the trim. If the glass is large and bulky, have a friend or two help you install it.

Step 5 - Replacing Trim

Take the trim you’ve removed and start pushing it back into place, beginning at one corner and moving around the edge a little at a time. When it’s properly positioned, you can make it secure with tacks down into the door.

To finish, you’ll need to remove any of the caulk that might have squeezed out. Gently scrape it up with a putty knife and then clean the glass of the sliding patio doors with glass cleaner. After completing the inside, go outside and repeat.