You might not consider installing a patio door to be a DIY project. The prospect of opening up a hole (even temporarily) in the side of your house should incite some sense of caution. But in many situations, this is a project that a homeowner can confidently attempt and successfully complete in a weekend.
The key factor that separates an “entry-level” patio-door installation from one that requires more experience or a contractor to complete is the amount of structural or rough framing that must be modified. In general, the less framing that you have to change, the easier the installation. For example, the most manageable installation is simply replacing an old patio door with a new one. Typically, all you have to do is order one that is the same size, remove the old door and follow the manufacturer’s instructions.
Replacing a set of windows with a door is more challenging, but not much. As long as the windows are framed in a rough opening that is tall and wide enough to accommodate a door, the only added work is removing the framing under the window. The same installation techniques apply whether you are replacing a single window with a single swinging patio door, a pair of windows with a sliding patio door or a larger set of windows with a set of in-swing French doors that feature a third panel of fixed glass on one side.
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Determine the Rough Opening Size
The first step in replacing a window with a door is to determine whether a door will fit within the existing framing. Measure the window rough-opening width and the distance from the bottom of the window header to the subfloor. The headers for a home’s windows and doors often line up, so there’s a good chance that the header will be high enough for your new door.
Measuring and determining the correct door size is second nature for an experienced contractor, but for the rest of us, deciphering the size charts in most window and door catalogs can be like cracking a secret code. The best way to ensure that you get the right door is to take your measurements to the store and let the retailer help you determine the specific size that you need.
If the existing rough opening is more than an inch taller or wider than the recommended rough-opening dimensions for a standard door, you will have to modify the opening size or combine the door with other door components to fit the opening.
Extra height can be especially useful when you are installing an in-swing patio door. A sliding door is installed directly on the subfloor, but you may want to elevate an in-swing door on a 3/4- to 1-in.-thick sill board so the door can easily swing over a rug or entry mat.
Check inside the wall for obstructions
Fixtures and utilities such as electrical lines and ductwork that are located inside the wall under the window must be removed or relocated to make room for the door. You also don’t want a heating and cooling vent in the floor to be in the path of the new door.
Visible fixtures are easy to identify, but you must also know what’s inside the wall. If you’re not sure, cut small holes between the studs to investigate. You’ll have to decide whether moving each obstacle is an easy fix or a major challenge that is not worth undertaking.
TIP: Consider hiring a specialized contractor to relocate utilities. Once the space under the window is clear, you can complete the rest of the door installation yourself.
Prep the opening
Once you’ve determined how to deal with any mechanical obstructions, you’re ready to order the door and apply for a permit from your local building-code authority. The next step is to remove the old windows and wall under the window. To minimize the amount of dust that spreads into house, hang plastic from floor to ceiling around the window and leave the window in place until after you’ve cut the exterior siding; you’ll cut the interior wall after you’ve removed the window.
Many homes built in the past 30 years do not have exterior window casing, and the siding butts up against the window frame. In these cases you have two choices. You can remove the siding on the sides and under the window and then recut and install the siding after the installation is complete, or you can cut back a few inches of siding on the sides and above the window and install new casing boards to fill the gap after the installation. Removing the siding exposes some of the sheathing around the rough opening, making it easier to remove the old window (especially if it was secured with a nailing fin) and allowing you to fasten the new door’s nailing fin and properly seal around the door.
After you’re removed the window and wall, prepare the new rough opening. Install additional framing as necessary to modify the rough-opening size and make the opening plumb and square. Finish the opening by applying flashing to the sill and sides of the framing.
Install the door
Most door manufacturers include very specific, detailed instructions for a new-construction installation. The steps are very similar for a retrofit installation. In addition to the instructions, many manufacturers also feature additional support information on their Web sites. Carefully follow the manufacturer’s instructions for installing and sealing the door.
The final steps are to fill the interior gaps with insulation and attach the interior and exterior trim. Low-expansion spray-foam insulation works best to fill gaps without putting pressure on the door frame.
Looking back to the day my friend inspired me to replace two windows with a sliding patio door, I’m amazed at how this simple switch has improved the way we use our home. Now I can’t imagine the house without that door. And I can’t figure out why I didn’t think of the project myself.