How Do I Replace an 8-Foot Sliding Glass Door?

Unscrew the screws in the brackets at the top and bottom of the fixed door (the non-sliding door). Slide the door to the center of the doorway and lift it out of the track.

Pry off the wooden retaining strip that runs along the top of the door frame, followed by the door casing on the inside of the house. Once you have removed the retaining strip and the casing, nothing is holding the door upright, so be prepared for it to fall into the house.

Pull out the nails in the exterior trim and remove the screws holding the threshold in place. Pull the frame out of the wall.

Examine the wooden frame for signs of rot. If you see rotten boards, pry them out or cut away the rotten pieces with a saw. Measure and cut pressure-treated 2-by-6 boards and nail them to the frame to replace any damaged sections you had to remove.

Cover the front edge and top of the threshold with flashing. Flashing is a strip of metal that protects the wood from exposure to water. Nail the flashing to the threshold with galvanized roofing nails.

Nail pressure-treated 1/2-inch-thick boards to the top and sides of the door frame if the new doors are smaller than the old ones. Replacement doors are often slightly smaller than the original doors.

Bend the nailing flange out around the top and sides of the new door frame. The nailing flange is a flap that you'll drive nails through to hold the door in place.

Apply a thick bead of silicone caulk along the middle of the nailing flange and on the threshold. When applying the caulk to the threshold, apply it around the perimeter of the threshold about an inch in from the sides. When finished, the caulk should be in a rectangular shape on the threshold.

Set the bottom of the replacement doors on top of the threshold and tilt the doors up into the frame, keeping the door centered in the frame. Drive a nail into the center of the nailing flange across the top of the frame to hold the door in place.

Hold a level against the sides of the frame to check the doors for plumb (vertically straight). If necessary, add shims between the wooden frame and the doors to achieve plumb. Once the doors are plumb, nail the doors to the frame by driving the nails through the nail flange, following the manufacturer's instructions regarding the spacing.

Re-install the door casings on the interior and exterior of the doors.