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Pet Doors: How (Not) to Install Them

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Making the hole in the wall for the dog (or cat) door.

Making the hole in the wall for the dog (or cat) door.

Dog or Cat Door Installation

Are you tired of letting your animal friend in and out of the house? If so, perhaps you've dreamed about one of those nifty pet doors but were deterred by the prospect of actually installing it.

Well then, be reassured! It's neither expensive nor difficult—even if, as was the case for my installation, not everything goes quite according to plan!

We knew we wanted a cat door for our new kitten and found that Petsafe makes a door suitable for a cat her size, available for less than $25. And we knew that we wanted to place that door in the wall. The package stated that the door was suitable for door and wall installation. Sold!

Cutting the Opening

The installation starts with locating and cutting the opening. I began with the inside, since wallboard is not critical for weatherproofing and is pretty easy to patch if necessary. I found the stud inside the wall, and carefully cut an opening of the size given in the door installation instructions. I was particularly careful to insure that I didn't cut into any electrical wires in the wall!

How I started cutting the opening for the pet door.

How I started cutting the opening for the pet door.

Consider What's On the Other Side

However, I should have been a little more careful yet. On the outside, as the above photo shows, my opening was crowded by an outlet box. Luckily, the box wasn't actually obstructing the opening, and could be freed from the wall by simply undoing a couple of screws, allowing me room to work. It could also be repositioned slightly when the door installation was complete.

But that was an error you don't need to make! Check inside and out before you cut.


Aligning Interior and Outer Openings

Here's view of the completed opening, with a bit of a view through into the room. Aligning the inner and outer openings is important, and not as easy as you might think when doing a wall installation. After all, the wallboard and siding are about four inches apart. I used a carpenter's square and got pretty close. The biggest problem I had came from the fact that the stud next to the opening was angled slightly, and I didn't notice that.

I had positioned the opening tight to the stud, and measured from there. The result was that when the door was installed, it was on a slight angle, too. That meant that it didn't want to sit neatly against the inner wall, as it should.

So, my recommendation would be to allow a little 'wiggle-room' if you are installing your door next to a stud or other obstruction inside the wall.

It's always nice to have the intended user check out the project while it's still in progress!

It's always nice to have the intended user check out the project while it's still in progress!

Don't forget to align the pet door properly.

Don't forget to align the pet door properly.

Avoiding Misalignment

Here's the inner portion of the door test-fitted into the opening. You can see the slight misalignment mentioned above.

You can also see the biggest problem with the installation—the door's built-in 'tunnel' is not long enough to reach the full width of the wall! Since the four-inch wall is a universal standard in North America, I have to disagree with Petsafe that this door is suitable for wall installation as is. It's a nice little door—affordable, yet well-designed and well-built. So far, it's held up fine and operated properly, opening and closing as it should without even creating a draft.

But for it to work in a wall, you need to add pieces not supplied. And that's what I did, as you can see below.

Ended up having to add something to my pet door to make it work!

Ended up having to add something to my pet door to make it work!

Spanning the Gap

I decided to span the inner width of the wall with roll aluminum. This is a product intended for roofing use. It's easy to work with, inexpensive, and not subject to corrosion problems. Best of all, I already had some on hand, left over from other projects. Below is a photo showing the measurement process. I've cut a length of the aluminum a bit longer than I'll need to run around the circumference of the opening. The rolled aluminum is then inserted into the opening to mark the depth of the wall, to which it must be cut in the other dimension. (If you look carefully, you can see a mark scribed into the metal, in line with my thumb.)

Inner portion of the door.

Inner portion of the door.

Here is the inner portion of the door, removed again in order for me to apply acrylic caulk around the outside of the 'tunnel.' My idea was to bond the aluminum to the plastic in this way, and to secure it temporarily from the outside with parcel tape.

You can also see that I've added caulking around the edges of the opening. This will need to be touched up with paint, of course.


With that done, I installed the door, with attached aluminum, and then added another 'U-shaped' piece of aluminum on the inside of the door.  This is the piece which the cat will actually be walking on.  This piece is secured to the siding temporarily with more package tape.


Weatherproofing the Pet Door

To complete the project the exterior needs to be weatherproofed. I chose to use a heavy-duty duct tape in white for this. Starting with the bottom, and taking great care to avoid wrinkles or bubbles in the tape, I applied overlapping layers of the tape.

It's a bit of a question mark for me how well this tape will hold up to weather and cat-traffic. But the tape is eminently replaceable if the answer turns out to be 'not so well.' I'll update this article to let you know when some time has passed.

In the meantime, though, we have a cat door that seems to be working well. The cat has discovered how to use it, with a little help and encouragement from us, and though we've had lots of rain since the installation, there does not appear to be a problem with leakage. So--and as usual for me--it seems that this project has been successfully 'muddled through.'

Hope it helps you and your furry friend!


Pet Door, Part Two

This arrangement worked well for us for about two months. I think it would have worked much longer, as it had not deteriorated in that period. But early in April of 2011, we had a disaster. I'll be writing about it specifically later, and so will not go into it here. But circuitously, events led to the presence of a stray beagle in our home. While we were away, said dog evidently panicked. The photo below shows the result.

A crazed beagle went through my pet door and made this mess!

A crazed beagle went through my pet door and made this mess!

Pet Door Options: Window vs. Wall

When the time came to replace the cat door, we decided to go with a window unit instead. They are considerably more expensive, but presumably are less susceptible to the particular 'failure mode' we had experienced. Online research led us to select an American-made unit from Ideal Pet Products, intended for use with sash windows. Ordering was simple, delivery was prompt, and installation—shown below—was fairly simple.


Which Side Goes Out?

First fitting of the unit into the window--and also my first mistake. Note the plain, unadorned surface on this inside view. Trouble is, there are locking knobs on this unit--it telescopes to adjust to the width of your window. I put them on the outside, where they would conveniently allow a burglar to unlock and remove the cat door, and so gain access to our home.

Oops. Note to self: knobs on the inside! That will also allow you to latch the flap from inside the room... (Yes, you can latch the flap. It's a 4-way adjustment: open both ways, locked, opening only inwards and opening only outwards.)


You can see in the picture above how the unit fits into the window. There are several sizes of these doors available to fit a range of window sizes, and useful measuring instructions are given on the Ideal website. I was a little apprehensive because our window was near the extreme of one size range, but as you can see, the fit was perfectly fine.


Weatherstripping the Window Unit

The cat door comes with ample weatherstripping to seal the gaps and eliminate drafts. Installation is a bit awkward, though I don't think that is the fault of the designers—it's just going to be a bit of a challenge to prop up the unit, and then to get the stripping cut to the correct length and pressed down straight, solidly, and without 'bubbles' along the entire length of the opening.

(As usual, the weatherstripping is a foam rubber strip with an adhesive back. You cut it to length, peel the paper off the adhesive, and press it down—or up, as in this case.)


Ah, success! Weatherstripping done, knobs and latch safely on the inside where they belong...

Wait, what's that cord coming from the outside?


Avoiding Drafts

Speaking of drafts, there's a source of them that you will have to deal with--the gap between window panes, as shown below. The cat door is in line with the inner pane, allowing cold air to infiltrate between inner and outer panes, into the room. There are instructions given for dealing with this situation, but since in our case the fit happened to allow a 'wood-to-wood' connection, I decided to use a solid strip to block this avenue. To do that I removed the latch hardware on top of the sash--a simple operation. This enabled the firm attachment of the various sliding bits with wood screws, increasing the security of the window.

You can see the strip in the picture below. It has been quite effective.


Partially (but not entirely) because of this change, I ended up with a few 'leftovers.'


How Long Did It Take?

All told, the installation of this unit probably took well under two hours, and could be done much faster. (I was very cautious at every step! Well, every step after putting the door in backwards initially, at least.) Installing this unit should be well within the capability of most readers.

We haven't subjected it to the 'crazed beagle' test--and will make strenuous efforts not to do so in the future. But this unit has performed well in all other respects. As you can see, the primary user is quite happy with it!

She's leaning toward the outdoors...

She's leaning toward the outdoors...

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.


Doc Snow (author) from Camden, South Carolina on April 27, 2019:

Love it, GadgetGirl! Simple, economical, effective. DIY at its best!

Too bad you didn't get pictures!

GadgetGirl on April 27, 2019:

We installed one of the first kind once. From the kitchen to the garage. My cats were not large. Very average, cat sized cats. That looked comically large pointing their toes to fit through the cat strainer we installed. So we removed it and went completely home made. Since it was not a security issue, we cut a nice rectangular hole they could get through without ballet. We closed the space between the walls with drywall, spackled and painted it so it looked just like the walls. We bought two small hinges, and two panes of plexiglass. The cats loved sitting in the garage and watching us in the kitchen. The longest part was waiting for the repainted drywall parts to dry.

Doc Snow (author) from Camden, South Carolina on August 07, 2018:

Thanks, 'Pet Door.'

Readers should be aware that the link given in the comment below is pretty clearly a commercial one. But it does offer useful tips even though it's all focused on one company's products, so I'm letting it stand.

mariebastian884 on January 30, 2013:

Thanks so much for this article! I have been searching for ideas on how to do my own and doors installation in Calgary and this is just what I needed! Thanks again!

Doc Snow (author) from Camden, South Carolina on September 10, 2011:

That's the idea, 'posh.'

What I should have measured--even once--was the door tunnel. Trust me, everything I *did* measure was done according to your advice!

Steve Mitchell from Cambridgeshire on September 10, 2011:

The rule is when fitting anything or cutting is 'measure twice and cut once' Looks like you could do to use this method when next fitting a cat door.Very informative though and will prevent other people making the same mistakes.

Doc Snow (author) from Camden, South Carolina on February 06, 2011:

Thanks, 'hello!" Yes, it would be good to find a unit that was better-designed for wall installation.

But I think that this will actually work well (and it is doing so now, as far as the cat is concerned!) It looks pretty good now, actually. (Which reminds me, it's beautiful today, so it should be a good day to get a better picture, so I can update that last image.)

The question I still have is, how will this hold up over time?

One last thing, which I found pretty funny.

The other day I was in the room and heard the cat door operate (the door is held closed by magnets, and there's a clicking noise when it opens or closes.) I looked around to see the cat. . . and instead found myself staring eye to eye with our 40-pound dog, Rambo! His entire head up to the eyebrows was inside the room.

He can't fit through the door, but apparently wanted to see what was going on inside. Good thing his head didn't get caught when he pulled it back outside!

Hello, hello, from London, UK on February 06, 2011:

That is certainly how it should not be done lol