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Install a Prehung Patio Door

Elevate your space with a new patio door that fits your style. Learn how to measure your rough opening and install your new unit.

Patio Door.

Tools & Materials

Product costs, availability and item numbers may vary online or by market.

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Measure for Your Patio Door

If you are installing a patio door in an existing opening, determine your door's rough opening dimensions before purchasing your new door. In some cases, it may be necessary to order a unit based upon the size of the rough opening.

To access the studs and measure for the rough opening, carefully remove the casing from the inside of the existing door opening. Take the measurement from the inside surface of the studs.

Measure horizontally across both the top and bottom of the rough opening, as well as vertically on each side. You may find that the rough opening is not square. When determining what size door you will need, use the smaller of each of your vertical and horizontal measurements. For example, if the left vertical measurement is 83 inches and the right vertical measurement is 82 3/4-in, use 82 3/4-in for the vertical measurement when determining your rough opening size.

Save the door casing to be reinstalled after the new door is installed.

Good to Know

Installing a patio door in a wall where no opening exists requires modifying a load-bearing wall as well as plumbing and electrical wiring rerouting. You should hire a professional.

Choosing Your Door

Several patio door options are available. Choose the door that appeals to you, depending on your situation and preference.

Hinged patio doors open like conventional doors, but feature large glass panes for a view of the outside. They may be installed as single or double doors, depending on the size of your door opening, but double door units are most prevalent.

Sliding patio doors are space-saving alternatives to swinging doors. Unlike swinging doors, which require that objects be set well away from the doorway, sliding doors require no room to swing. Sliding patio doors usually have one door that is fixed and another that slides. They often have aluminum frames, although they may be vinyl, steel or wood.

Folding patio doors are great if a wide, open space is what you’re after. These doors are designed to fold away neatly and help to fill your space with natural light. They may be installed as double or multi doors, the more panels you have, the more natural light. These panels can even fold around 90 degree corners to maximize the width of the patio opening.

Any type of door may be characterized as having "right-hand" or "left-hand" operation, as viewed from outside, so you must know which side you would like to operate. Purchase your patio doors with the door panels already installed in preassembled frames. This will greatly simplify your project.


Use our Patio Doors Checklist to learn about more options and help you select the right door.

Install a Prehung Patio Door

There are some basic principles involved in the installation of preassembled patio doors. Detailed installation instructions will be included with the particular door you choose.


Need help? Professional installation available through Lowe’s.

Good to Know

These are general instructions, but always follow the manufacturer's installation instructions and safety precautions.

Step 1

Test fit the patio door in the rough opening. From inside, make any required adjustments and shim as necessary so the door frame is plumb and square.

Step 2

Cut a piece of drip edge, sometimes known as drip cap, to the width of the rough opening. Apply silicone caulk to the drip edge and insert it along the top of the rough opening, between the siding and the existing house wrap.

Step 3

Prepare a sill pan to fit in the rough opening using either step or roll flashing. Apply caulk to the bottom of the rough opening and press the sill pan into place.

Step 4

caulk applied to rough opening of door.

Apply silicone caulk around the edges of the rough opening where the siding meets the house wrap. Also apply several liberal beads along the bottom of the opening where the threshold will sit. For tips on applying caulk, take a look at our DIY Basics video: How Do I Use Caulk?

Step 5

two men tilting a patio door into place.

With a helper, tilt the door up into the rough opening. Shim the door from inside as necessary to allow the door and frame to sit square and plumb. If there are gaps under the threshold, add additional shims under the door every 6 inches or so for support. Install shims under any screw holes for the threshold to avoid having the screws pull the threshold out of shape.

Good to Know

Make the shims snug, but don't force them in place. Forcing the shims could distort the frame and cause a bow along the threshold.

Step 6

Installing shims

Install shims around the edges and top of the door frame. Space them approximately every 12 inches. If you are installing a swing-style door, use additional shims to support the strike plate area of the door frame. Make sure everything is level and plumb. Check out our DIY Basics video: What Do Level and Plumb Mean?

Step 7

driving screws into the hinge.

Secure the door by driving screws into each hinge.

Step 8

Ensuring that the brick mould is flat against the framing lumber from outside, drive 10d finishing nails through the brick mould into the framing every 12 inches or so and in the corners. Countersink the heads to facilitate applying the finish later.

Step 9

From inside the house, drive 10d finishing nails outward through the shims and into the framing. Again, countersink the nail heads.

Step 10

scoring the excess shims.

Score the excess shims with a utility knife and snap them off so they're flush with or below the door frame.

Step 11

Screw the threshold to the floor.

Step 12

Apply a minimal-expanding foam insulation to seal the gaps between the doorframe and the wall. After it sets, trim the excess with a putty knife. Cover the insulation with trim and apply a bead of caulk to the joint between the trim and the interior wall.

Good to Know

Avoid direct contact with your skin. Wear appropriate protective clothing and equipment when working with insulation. Watch our DIY Basics video, How Do I Use Spray Foam? for tips.

Step 13

caulk around the exterior door casing.

Caulk completely around the exterior door casing. Use a premium quality, paintable silicone caulk.

Step 14

Fill all nail holes and finish the door and frame as soon as possible after it is installed.

Watch DIY Guy tackle How to Replace a Door.