Project Guide

How to Install a Sliding Door

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Choose the Right Size Sliding Door
A sliding door inside a home

Before you begin the door installation, you’ll want to choose the right size exterior doors to ensure they fit in your space. Many homeowners choose to replace sliding glass doors with newer models as a simple design update. Here’s how you can know what size door to get:

  • Remove the casing from the existing door frame to locate the studs. Set the casing aside somewhere safe.
  • Measure horizontally across the top and bottom sides of the opening, starting from the studs. Take measurements vertically on both sides.
  • Use the smallest measurements to fit your new door. For example, if you get 80” at the top and 81” at the bottom, use 80” as the measurement for the best possible fit.

Once you have these measurements you can begin shopping for new patio doors that fit the look of your home.

Prepare the Opening
A frame opening to the outside patio of a home
  • Take a minute to test fit your prehung sliding door to the opening. Make any adjustments from the inside and use shims as needed to ensure a secure fit.
  • Create a piece of drip edge the size of the opening. Apply silicone caulk to your drip edge and put it along the top of the opening between your siding and house wrap.
Caulk the Opening
A man caulking the opening of a frame for sliding door installation
  • Create a sill pan to fit in the opening using roll flashing. Add caulk to the bottom edge of the opening and firmly press the sill pan into the caulk.
  • Put silicone caulk around the edges of your opening where your siding and house wrap meet. You’ll also want to put a few drops of silicone caulk at the bottom of the opening.
Position the New Door
Two people positioning a new sliding door in a frame opening
  • Begin positioning the door into the opening from your exterior area. 
  • Tilt the door into the opening with the bottom side going in first, using shims as necessary to create a secure fit. 
  • Use shims under screw holes to help keep your threshold in good shape.
  • Place shims around the edges and top of your door frame every 12 inches. Place your door hinges and secure them in place with screws.
Secure the Door
A man securing a sliding door in place
  • Check that the brick mould is flat against the frame on the outside. If it is, use 10d finishing nails to secure the brick mould and framing roughly every 12 inches or so. Countersink the nail heads.
  • Move inside the house and use 10d finishing nails, driving them outward through the shims and into the framing. Countersink the nail heads.
  • Use a utility knife to cut the excess shims. Break or cut them off so they’re flush with the door frame. 
Secure the Threshold
A man securing the threshold of a newly installed sliding door
  • Secure the threshold to the door with screws. Make sure the screws aren’t exposed.
  • Use expanding foam insulation to seal any gaps between the door frame and wall. Use a putty knife to remove the excess after it dries. 
  • Cover the foam insulation with trim and add a small amount of caulk to the visible joint between the trim and interior wall area.
  • Use paintable silicone caulk around the exterior door casing. Fill all nail holes to finish your door frame as desired. 

Installing a sliding door can help beautify your home and make any room a more enjoyable space. Seek the help of an experienced professional if you’re unsure of how to proceed with the door installation. Installing the door incorrectly can lead to issues down the road, so take your time and get each step right if you choose this DIY option.