Removing a pet door is the easy part, patching the hole is the tough part. Most people look at a small dog door hole and think it will be a fast job. Consider this: you will need to install insulation in the wall, sheathing, and whatever material your house has on the exterior (stucco, etc) and exterior paint. For the inside, you will have drywall, tape, texture and a second color of paint. Somehow this isn’t going to be a one hour job.
There is a sequence to follow for this type of job. Obviously, you first should remove the dog door. Depending on the type of door you have , you may need to remove some screws that hold the ends of the door together (they sandwich the wall), and then cut through the caulking at each surface. If you have a homemade dog door, you will probably have to remove any molding around the opening and then pry out any pieces that form the opening. What you will have left is a square opening.
You will need to install some pieces of 2”x4” or other strips to act as nailing surfaces. Cut your sheathing to fit the opening, nail it to the strips and add the exterior surface materials (its always a good idea to close in the exterior first).
Add insulation in the opened wall, and then drywall the opening. Then you can texture and paint the patch.
Since a dog door cut through your wall is an opening into your house, it should be as weatherproof as you can make it. For this reason, I like the store-bought dog doors that have 2 flaps on them. These have a flap on the interior of the wall and the exterior of the wall.
Cutting a hole in your wall is a big deal, and so you want to make sure that the outside actually stays outside. I’ve seen people make their own dog doors, and they really look like they are homemade (remember too that this is a potential entrance point for a burglar).
Store-bought dog doors get assembled in halves. There is a wall kit that you can buy (usually sold as an addition to the dog door) that bridges the gap between the two halves. This kit keeps all of the wall insulation in the wall and makes for a flawless installation. The two halves mate with the wall kit and then you install long screws in each of the corners to hold it all together.
I would suggest running a bead of caulking on the exterior of the dog door where it meets the wall. For a smooth surface wall, like siding, you can get away with a lesser amount of caulking. For rough surfaces, like stucco, use a thick bead of caulking and then wet your finger and push it into the crevices to fill the gaps.
If you have the need to install a dog door you don’t always have to cut a hole through your wall. You may be able to cut a hole through a side door. Some homeowners will install the door in a garage door and then out the side door. Just be aware that cutting a hole in your garage door compromises the fire rating of it. Some people don’t care, but when you go to sell the house, it will likely be caught by an inspection and you will have some choices to make.
If you plan on installing a dog door through the door anyway, it should take you about 30 minutes. The pet doors come with a template and you can trace the pattern on the door. I would drill a hole in each corner of the pattern so that the saw blade has some relief in the cut. Use a jigsaw with the correct blade. It’s a good idea to cover the shoe of the jigsaw with something that will prevent the shoe from scratching the door as you make the cut. Blue painter’s tape seems to work pretty well.
Start in one corner and just connect the holes that you have drilled. When the hole is made, you can install the door halves and just screw it together.
If you are installing a dog door, once you get over the fear of cutting a hole through your wall, you will need to make sure the installation is weather tight. I prefer to use a store-bought dog door rather than a home made door, but with either one, you will need to make sure that it will keep out the elements.
I like dog doors that have two flaps, one on the exterior side of the door and one on the interior side of the door. These are held together with an extension kit that keeps the wall insulation in place and makes for a clean installation. As for being weatherproof, look at the exterior side of the dog door.
The well made doors have a means to hold the flaps in position, such as a small magnet. When the dog passes through the door, the flap will move once or twice and then come to rest just above the magnet. It is crucial to use caulking around the perimeter of the exterior side of the dog door. As rain water hits the unit, or hits the wall above the unit, the water will run down and seep into the wall opening. This is why caulking is so important. It will prevent the water from entering the wall.