Installing a Sliding Glass Door

The procedure works for rough openings up to 3 1/2 feet wide. For a broader opening, such as a sliding glass door (shown here) or a large bay window, you need larger headers: 2x8s for up to 5 feet of length, 2x10s for up to 6 1/2 feet, and 2x12s for up to 8 feet. Because an exterior wall bears the weight of an upper floor or the roof, you must devise a temporary support to carry the load while you modify the wall. Install braces, as shown below, and protect flooring with plywood or planks.

Replacing a window with sliding glass doors that open to an outdoor living area will entirely change a homes character. So before you settle on a location, consider privacy, light, ventilation, and the traffic pattern. Remember that glass loses heat rapidly at night and gains heat rapidly on sunny days. Minimize energy losses by choosing units with insulating glass and by locating them on walls away from prevailing winds.

Sliding glass door units are framed in aluminum, steel, wood, or wood clad with vinyl on the exterior. Standard sizes are 5, 6, and 8 feet wide by 80 inches high. Be sure you can count on good weather the day you cut through the exterior of the house. (Because it’s easier to remove framing from a wide opening if you first pull off the sheathing and siding, your home’s interior will be exposed throughout most of the project.) Also be sure to have help available to lift the header into position and install the door. If your sliding glass door will replace an existing window, you can remove the old unit intact, sash and all. Wait until the studs are exposed on both sides before prying them away from the window frame. Cutting a new opening in a brick-veneer wall calls for quite a bit more work—probably a job for a mason.

Tools: Hammer, chisel, pry bar, nail puller, carpenter’s square, reciprocating saw, nail set, level, drill, circular saw, caulking gun, and tools to repair broken plaster or drywall.

1. Remove the drywall or plaster. Mark cut lines for an opening 3 inches wider than the rough opening, running from floor to ceiling. If possible have at least one of the lines run alongside an existing stud. Cut away the drywall or plaster and remove or relocate any wiring, plumbing, or heating ducts. If necessary slip in and attach a stud on one or both sides.

2. Install temporary bracing. Set a piece of plywood on the floor to protect it. Build a stud wall and raise it into position, no more than 2 feet away from the rough opening. Use shims to make the temporary wall snug. Keep this bracing in place until you have finished framing the opening.

3. Cut the siding. With a reciprocating saw, cut the siding and sheathing at the top and the sides. Then cut through the toe plate and remove it. Cut through the siding at the bottom of the opening.

4. Install a header. Cut jack studs to the height of the rough opening and attach them to the king studs on each side. Check each side for plumb and see that the rough opening is the correct size. Build a header out of 2x lumber and plywood, set it on the jack studs, and attach it with angle-driven fasteners.

5. Mark and cut the siding. Place the door frame in the opening. Check for level, plumb, and square. Trace around the frame and cut through the siding (but not the sheathing). Cover all bare wood with roofing felt (tar paper) or building wrap and reinsert the door frame. Secure the frame loosely with screws.

6. Plumb the frame. From the inside use shims to make the door perfectly level at the top and bottom, plumb at the sides, and square at the corners. Make sure that you do not bend the frame as you tap in shims. Fasten the frame and set in the door panels. Insulate between the frame and the opening.

7. Add molding. Molding bridges the gap between the frame and the siding. Install exterior molding and caulk the joints. Inside, patch the wall and install molding.

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