This story shows how to install a patio door.
A sliding or swinging patio door installs using many of the same steps as for a standard entry door. However, because it is so large, requirements are more exacting. The frame must be straight and square all along its length; it is particularly important that the sill be straight and level. Some patio doors are sold with the frame knocked down, so you will need to assemble it. It may be easier to purchase a door with the frame already assembled.
The steps that follow show a sliding patio door. If you are replacing a patio door that operates smoothly, you may not need to alter the rough opening. However, if the old door was difficult to operate, check the rough opening carefully.
After the rough opening is prepared, about 4 hours
Tape measure, drill, hammer, level, tin snips, chisel, circular saw, flat pry bar, stapler, caulk gun, screwdriver, nail set, handsaw
Measuring, sawing, fastening, leveling
Assemble the door frame if needed. Enlist a helper.
Patio door, metal drip edge, roofing felt or building paper, mason's line, exterior brick molding, interior casing, casing nails, finishing nails, composite shims, exterior caulk, wood filler, insulation
Remove the old patio door. If you make a new opening, install a temporary support. Measure the diagonals to check the opening for square (they should be exactly equal). Use a long straight board or a string line to check for high spots in the sill and low spots on the header. When measuring for a new door, use the shortest measurements. Use shims to level the sill.
On a wide opening like this, also check that the sides are in the same plane. If one side leans away from the house and the other does not, the opening is "cross-legged" and the door will not slide smoothly. Stretch two lines diagonally across the opening; they should just touch where they cross. If they don't, try using a small sledgehammer to move one or both sides a bit. Otherwise you may need to remove siding or drywall on one side and adjust the framing.
Unpack the door and assemble as necessary. If the sliding panel is in place, remove it by lifting up and tilting the bottom out. It's usually best to leave the fixed panel in place; it makes the door heavy, but it helps keep the frame square. Some packing blocks should be removed; others should be left in place until you're ready to install the molding. Refer to the manufacturer's instructions.
Check the door frame for level, square, and plumb; continually recheck as you shim. Tap in pairs of shims every 12 inches on the sides and the header, and every 8 inches on the floor. Tack (partially drive) nails or screws to temporarily hold the door in place. Reinstall the sliding panel and check for smooth operation. If your patio door has brick molding already attached, mark the siding for cutting now. Back out the fasteners and remove the door.
Just before you finally install the door, apply three beads of exterior caulk on the sill. Apply extra-thick caulk near shims to be sure the bottom of the threshold seals against the sill. Tilt the door back in place. Check that the threshold is straight and even. Shim the sides and the header.
If the door's jambs are the right width, the front of the jambs will be flush with the wall surface. Often, however, the jambs fall short of the wall surface. If so, make sure the distance between the jamb face and the wall surface is consistent all around, so you can fill in later with trim ripped to fit. If the jamb stands slightly proud of the wall surface, you will need to plane the jamb.
Install the sliding door and test for smooth operation. The gap between the door panel and the frame should be consistent at all points. Drive screws or nails to attach the threshold. If you see the threshold flex slightly when you slide the door, install additional shims as needed.
Use a handsaw to cut the shims flush with the framing or the wall surface. If the jamb does not come flush with the wall surface, cut the shims flush with the jamb edges. If the sill does not stick out as far as the brick molding, rip-cut a piece of siding or pressure-treated lumber to fit and nail or screw it in place. You can install a kick board below the sill.
Mark a 1/4-inch reveal around the exterior edge of the jamb. Hold trim against the door for marking. Apply the trim using 10d galvanized casing nails when nailing into framing and 6d if nailing into the jamb. Use 10d galvanized casing nails for attaching integral brick molding. For flanged units drive screws.
Rip-cut the jamb extender. To ease final installation, glue the extenders to the interior casing in advance. (In this case the old casing could be reused because the replacement door was slightly smaller than the original door.) Be sure to clamp each piece even with the casing.