How to Build a Patio Pet Door

A patio pet door is an ideal solution for pet owners. Rather than cut into the wall to insert a doggie door or cat flap, a patio pet door can slip into your existing sliding glass frame, with the glass door pulling up to it to seal out the cold or heat of the outdoors. However, patio pet doors are expensive and most of them do not have a lock to keep out potential burglars. Worse still, if you have an old or custom patio door with unusual measurements, chances are you won’t find a patio pet door anywhere. By building a patio pet door, however, you can custom fit it to your needs, and install an internal locking device as well. It’s an easy project that will take you about 2 hours and save you 75% over the cost of buying a standard low-end patio pet door.

How to Build a Patio Pet Door: Step #1

Begin by purchasing a basic pet door (doggie door or cat flap) from your pet store. Typically these basic pet doors are inserted in a standard, wood door. They are inexpensive and made of a simple plastic frame with a weather-sealed pet flap.

How to Build a Patio Pet Door: Step #2

Measure the height of the inside frame of your patio glass door. Do not worry about the rails as the patio pet door will be slim enough to fit on one side of them. Next, see what the width measurement is for the pet door you bought (this should appear on the box). These two measurements will determine the width and length of your patio pet door; however be sure to add 10 inches to both of them (you’ll soon see why). In other words, your patio pet door length will be: Inside glass door frame + 10 inches. While the patio pet door width will be: standard pet door width + 10 inches. Buy plywood at your local lumber or home improvement store to fit these measurements. When they cut the plywood for you, be sure to ask them to cut another thin slice of plywood to fit the width measurement but with a length of 4 inches. This will be used as a supporting shelf in the final steps of this project.

How to Build a Patio Pet Door: Step #3

When you open the pet door box you will find a sheet of paper that you can place over the plywood to draw an outline of where the patio pet door will sit. Because you have added ten inches to the width, you should have 5 inches on either side of the pet door. With a saw, cut out the square opening. Then place the frame of the pet door on either side of the opening and screw them together with the hardware provided.

How to Build a Patio Pet Door: Step #4

In order to slip your patio pet door in and out of your existing patio glass door frame, you will need to cut the patio pet door into two pieces. This is why you added 10 inches to the length earlier. Begin by sawing your patio pet door into two pieces, with the top piece being far smaller, at around 15 inches long. Next, fit the two pieces of your patio pet door into place inside your glass door frame. Now with a pen, mark a line to indicate where the top portion of the patio pet door overlaps with the bottom.

How to Build a Patio Pet Door: Step #5

Over the line you have drawn, glue the supporting shelf you got at the lumber store. Once the shelf is dry it will hold the top pieces of the patio door in place when you fit them together. To increase the stability of the two pieces, screw a flat metal bracket into the shelf using a cheap door knob. Each time you fit to two pieces together, go ahead and slide the flat metal bracket up. When you want to remove the door, slide the bracket out of the way. When the bracket gets too loose, just tighten the door knob over it. And use the door knob to help you grab or hold the patio pet door.

How to Build a Patio Pet Door: Step #6

Paint the patio pet door to match the frame of your glass patio door. This will help the patio pet door blend into the original door and seem like a custom extension. Finally, cut a piece of molding or a broom stick to fit between the sliding glass door and its frame, creating a simple deadbolt. This will make it impossible for someone to slide the glass patio door open from the outside.