How to Install a Dog Door

When life gets busy, it’s easy to miss the signals that a dog needs to go outside right now. And when the message doesn’t get through, the result can be a nasty mess. That isn’t a worry with a dog door, fitted into either a human-sized door or a wall like the one at right, because it gives your dog the freedom to come and go at will.

Providing a pet with its own portal can also save on heating and cooling bills—a small door, when opened, allows less interior air to escape than a big one does—as long as it is weatherstripped and closes tightly on its own. The DIY pet door above has two saloon-style doors that close quickly and don’t need much pressure to open. When the family is away, a metal plate inside deters intruders.

This Old House general contractor Tom Silva and host Kevin O’Connor will show you how to install a dog door in a wall using a PlexiDor dog-door kit for Soleil, the Newfoundland at the Arlington Arts and Crafts TV project. These kits are available in a range of sizes for breeds big and small—even cats. Whichever size you choose, the door takes only a few hours to put in. Before you know it, your pet will be enjoying the ability to go freely in and out whenever it pleases.

Shown: When coming inside, Soleil pushes the saloon doors inward and enters the laundry room. Inset: Soleil now goes outdoors anytime she wants through the dog door at the Arlington Arts and Crafts TV project.

PlexiDor Wall Series, from $332

Steps for Installing a Dog Door

Step 1

Day-to-Day Timeline

SATURDAY Install the dog door (Steps 2-20).

SUNDAY Install exterior trim and siding (Steps 18-20).

Step 2

Find the Best Location

Cut an inspection hole in the drywall near the center of where you want the door to go. Stick in a straightened coat hanger to locate any studs. Here, an outlet box cutout showed where one stud was. Rest the door template’s bottom edge on the floor, check it for level, and tape the template to the wall in a stud-free spot, if possible. Drill a horizontal 3⁄8-inch hole completely through the wall at each template corner, as shown.

Step 3

Cut Out the Drywall

Guide a reciprocating saw blade into the holes and make straight cuts between them, as shown. Remove and save any insulation. If no studs are in the opening, go to Step 7. Stuff or spray insulation in any voids behind the drywall and put 2x blocking behind all unsupported edges around the opening. Toe-screw each 2x to the sheathing, then screw the drywall to the 2xs.

Step 4

Remove any Studs

If studs are in the way of the dog door, make room for a header by cutting out a 5 ½-inch-wide strip of drywall above the opening. Extend this cutout past both sides of the opening to the nearest stud. In this case, Tom cut through the stud under the window, and saved the cutout piece of drywall. Then, using a reciprocating saw, he cut out the exposed studs, as shown, and used a pry bar to lever them off the sheathing.

Step 5

Build in a New Header

To support the cut studs, build a header in place by screwing 2x6s to the sheathing and to each other, as shown. Here, Tom used three 2x6s, plus an additional filler strip made of 1-inch foam insulation, to make the header flush with the framing. Rest one end of each board on the cut stud under the window.

Step 6

Add Support

Both ends of a header require support, so Tom cut a short 2×6 jack stud to fit tightly between the other end of the header and the bottom plate. After hammering the jack into place against the face of a full-length king stud, he fastened them together with 2 ½-inch deck screws, as shown. Then he added leftover insulation from Step 1 and filled any voids with spray foam. A second jack stud, set in line with the drywall’s cut edge and toe-screwed to the header and bottom plate, ensures that the dog door’s inner frame has solid backing on all four sides. Screw the saved strip of drywall onto the header.

Step 7

Cut the Sheathing

Remove the siding and house wrap within the area bounded by the holes made in Step 2, and 8 inches beyond. Next, cut through the sheathing on the top and sides of the opening with a reciprocating saw; use the framing alongside the opening to guide the blade. Draw a horizontal line 1 ½ inches below the lowest holes on either side, and cut along it with a circular saw. Push out the scrap sheathing, as shown.

Step 8

Rough-in the Sill

Trim the bottom of the opening so it’s flat and slopes to the outside, as shown. Let the bottom edges of the sheathing and drywall guide the blade.

Step 9

Patch the Drywall

Using a taping knife, fill the screw holes and any cracks around the opening with joint compound.

Step 10

Attach the Interior Panel

Fasten the door to the blocking with the screws included in the kit.

Tip: The door’s height above the floor should be 2 inches greater than the height of the dog’s shoulder. For door-sizing guidelines, see the Size Chart.

Step 11

Weatherproof the Opening

Using a utility knife, cut a piece of builder’s felt wide enough to reach from the bottom edge of the interior door panel, across the sill, and 8 inches below it. Staple the felt to the sheathing only, not to the sill. Cut two strips of felt 8 inches wide and long enough to reach from 3 inches above the top of the opening to 8 inches below the sill. Slip the top 3 inches of each strip under the existing house wrap, align their long edges with the edges of the opening, and staple them to the sheathing, as shown.

Step 12

Flash the Sill

Cut the bottom piece of felt where it meets the face of the stud on each side of the opening. Press the resulting flap down flat against the sill so its top edge touches the door panel, as shown. Protect the exposed wood in the opening by stapling a strip of builder’s felt to each stud face and to the underside of the header. In this installation, Kevin also stapled the siding’s yellow rainscreen mesh up to the edges of the opening.

Step 13

Install the Outside Frame

To prevent water from getting behind this frame, squirt a bead of spray foam into the frame’s inside corner around its entire perimeter, as shown. Immediately press it into place in the opening.

Step 14

Fasten the Frame

As soon as the frame is set, screw it to the studs on the sides of the opening, as shown.

Step 15

Cut the Metal to Fit

The aluminum liner provided in the kit is bent in the factory to fit the door width, but it has to be cut in the field to fit the tunnel between the inside door panel and the outside frame. Mark the cutline, then make the cut using a jigsaw or an angle grinder fitted with a metal cut-off wheel, as shown. Here, Tom uses the edge of a piece of scrap trim to guide the cut.

Step 16

Apply Spray Foam

Squirt a bead of foam over the sill flashing and partway up the sides, as shown. The foam acts as an adhesive, eliminating the need for fasteners in this vulnerable location.

Step 17

Set the Sill Liner

Squeeze a bead of silicone sealant, supplied in the kit, along the outside edge of the liner’s bottom face. Now remove the metal’s protective film and fit the liner under the bottom edge of the inside frame, as shown. Press down firmly on the liner to ensure that it’s securely attached and that there aren’t any gaps in the sealant.

Step 18

Attach the Head Liner

Following the same procedure used in Step 16 and 17, install the head liner piece, as shown. Because it’s protected from rain, it’s okay to screw this liner to the top of the outer frame.

Step 19

Fit the Side Liners

Using a jigsaw or an angle grinder, cut each side liner to fit the depth of the tunnel, and trim the lower ends to match the angle of the sill. Cut the upper ends to overlap the ends of the head liner. Apply beads of silicone and spray foam, remove the protective film, and slip the liner in place, as shown.

Step 20

Fasten the Sides and the Exterior Trim

Screw the lower and upper ends of each side liner to the outer frame, as shown. Now, nail up the exterior trim that surrounds the dog door so it overlaps the face of the outer frame (see opener). Reinstall the siding up to the trim.

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