How To Install a Cat/Dog Door on an Exterior Door


If you are anything like me, you have some pets that you keep inside that need to go outside every once in awhile.

Our dogs go outside a few times a day and our cats are out even more.

Unfortunately we do not have a cat or dog door for our animals to go through.

And all of our exterior doors are metal doors.

So, can you install a cat or dog door on an exterior door.

The answer is yes. You will just need to pay attention to the size of a cat or dog door you purchased and make sure you have all the appropriate tools.

Follow the below steps and you’ll find how easy it is to install a cat/dog door.

Make sure your pet door is the correct size

There are a few things to consider when purchase a pet door.

First, measure how thick your exterior door is.

Most pet doors will be wide enough to fit your door, but you can never be too careful before you start cutting.

Second, make sure the pet door is going to fit the size of your pet.

Not all animals are the same size, so make sure you get a dog door for your dog and a cat door for your cat.

Otherwise, you might end up with a door far too big for your cat or way too small for your dog.

Amazon is pretty good at giving you the information you need.

For example, Amazon lets me know the cat door found here can fit in doors 1/2 – 2 inches thick. It is also meant for cats up to 15 lbs.

Consider what kind of entry you want for your pet

There are generally two types of entries of cat doors: 2-way and 4-way.

The 2-way lock is the normal locked or unlocked.

The 4-way allows you to lock a particular entry way.

For example, let’s say you only want your cat to be able to come inside. Once the cat is inside, you no longer want the cat to go out.

The 4-way lock allows you to let the cat come in, but not go out.

It is the same way for going out: you can let the cat go out, but not come back in.

This can be a handy feature if you have a cat like our Dandelion, who likes to go out at night and come back in at her own timing.

You have another option which is the microchip doorway, which only lets your own pet in or out of the door because they have the microchip embedded in them.

This might be a great option if you live in an area where cats run wild.

The microchip option is a little more on the expensive side, costing $80 or above, depending on how fancy you want to get.

The 2-way and 4-way cat doors are typically between $10-$20.

Dog doors are not as fancy, which typically come with just a flap.

But you want find pet doors that are both for cats and dogs, if you need to accommodate both.

Tools you may need for the install

  • Marker

Your pet door should come with a template.

The template gives you the shape and size of what the pet door is going to be.

You will need the marker to outline the template on your door.

  • A tool to cut through the metal door.

Different options for cutting through the door include: jigsaw, reciprocating saw, or grinder.

  • Gloves
  • Protective eye wear

Because you will be cutting into metal, there will be sparks and hot metal.

So, make sure to have gloves and protective eyewear handy to protect you when you are cutting. You will not want to touch hot metal with your bare hands when done cutting.

  • Drill

When you’ve got the template cut out from the door, you will want a drill to make some holes on the other side of the door.

  • Two sawhorses (optional)

When you go to cut the door, you have two options: you can either cut the door while it is still hanging or you can take the door down and place it on two saw horses to do your cutting.

If you are not completely confident in your cutting skills, like me, you might want to take your door down and then cut.

If you feel perfectly capable of cutting while your door is still standing, no need for the sawhorses.

  • Hammer and flat head screwdriver (optional)

If you are taking the door off, then you will need a hammer and flat head screwdriver to take the door off of its hinges

  • Metal file

You will need something to remove the inside of your door once you have cut it.

The metal file will help you remove the insides of the door.

Installing the pet door

Once you’ve reviewed the above and have all your tools ready, it is time to install the pet door.

  1. If you’ve chosen to take the door off, do that first and place it on the sawhorses. You will take the door off by using a hammer and flat head screwdriver to remove the door pins from the hinges. Then place the door on the sawhorses. If you are leaving the door in place, move on to number 2.
  2. Place the pet door template on the exterior door based on the instructions given with the pet door. You will typically have the pet door at least 3 inches from the bottom of the door, but make sure to follow the instructions that came with the pet door.
  3. Once the template is in place, outline the template using your marker.
  4. Drill holes in each corner of your outline. Make sure the holes are made all the way to the other side of the door. This will give you the corners on the other side where the template should go.
  5. Use your jigsaw, reciprocating saw, or grinder to cut the outline made in point 3 on one side of the door.
  6. Go to the other side of the door (flip over on the sawhorses if you removed the door from its hinges) and place your template with the four drilled holes on the four corners, outline with your marker, and cut again.
  7. Steel doors are typically a steel frame with a paper honeycomb, fiberglass, or foam insulation on the inside. If the door was steel right through, it would be too heavy for residential applications. Once you have both sides of the door cut, you then need to cut out whatever is on the inside of the door. This would be the time to pull out your metal file and use the metal file to slowly cut away the insides of the door.
  8. Place your pet door into the holes you just cut to make sure it fits appropriately. If it does, move onto the next step. If not, cut to have the pet door fit.
  9. Follow instructions provided with the pet door to keep it in place. Most will provide screws to screw the pet door into the human door, but review instructions to make sure.
  10. If you removed the door from its hinges, place it back on the hinges and put the pins back in place.
  11. Last, teach your pet to use the new pet door. This typically means using a treat to coax your pet to go through the door multiple times until they learn the door is for their use.

And that is it. Your pet will love you now that they have free access to these areas they didn’t before.

And you won’t have to let your pet outside a few times a day.

Other resources

5 minute step by step video to install a cat door

Bill Lantz

Bill Lantz is a database analyst by day and a weekend warrior by... weekend. He's currently building up his own miniature homestead in Central Utah with his wife and six kids. Some of his interests include knowing random trivia about films, reading history books, and playing video games with the boys.

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