This past spring I found I needed to install a dog door. I was going to be away on a short trip, and although my neighbor was willing to come over to feed my dog, the weather was still too cold for her to stay outside. A dog door which would allow her to come and go on her own (she freaks when shut inside with no human for company, even for a few minutes) seemed the right answer.

However, cutting a hole in the front door (well, a bigger hole in this case; I already had a blocked-up cat door there from very long ago) is a serious commitment. It affects both the security and weatherproofing of your house. Standard commercial dog doors are a) expensive and b) while they are reasonable at keeping the cold out on still days, they leak around the edges in a stiff wind, which we get a lot of here. I'd seen a two-flap design years ago, and even made a small one that worked okay out of car floor mats, so I decided to scale that up, using a cheap vinyl set of mats from Big Lots.

Long story short, I found that even when reinforced, the mats didn't hold up very long, though they got me and my dog through that weekend trip. However, I had already cut the big hole in the door, so it seemed a shame not to build something that would work over the long term. I slapped a piece of plywood over the opening to keep the weather out and went back to the drawing board.

First of all, the theory. A dog door that overlaps the main (human) door around its edges when closed is inherently more weather-resistant than one that just fills the opening. Only problem is that—unless you have a very clever and agile dog—this only works one way. With the two-flap solution there are in fact two dog doors: (1) the larger one which overlaps the outer surface of your main door, and which can be pushed open from the inside, and (2) a slightly smaller one that fits inside the other and can be pushed open from the outside. Both have magnetic catches that keep them in place when not in use.

Step 1: Materials & Tools

Plywood (14” x 17” x ~1/4”)
Multiwalled plastic sheet (10” x 13”)
Magnets (2) (I used 3/8” x 3/8” x 1 7/8” magnets I found at Home Depot)
Butt hinges (2) with 12 ½” or 5/8” screws
¼” x 10” oak dowel
Fine wire
Eyebolts (2)
Scrap wood
~5” strip of galvanized sheet metal  & 4 - 3/4” screws
Wood glue
Finishing nails (optional)
Silicone sealant
Duck tape
Isopropyl alcohol

Utility knife
Rulers & squares
Clamps (optional)
Chisels and mallet (optional)
Thanks for idea I still have a few finishing touches to add great idea , a found a piece of plastic the day after I had read your article must have been a sign cheers Rob and Spud ?
<p>AHHH this picture is the one that made the design click and make sense to me. THANKS!</p>
Great write up, and descriptions of construction. <br> <br>I've got a custom dog door for mine and am always looking to improve it. <br> <br>But, I had to read this three times looking for the 'second flap' - since I only saw the single flap of material.. I see now that there's only one flap, mounted inside the outgoing frame. <br> <br>In essence, the ingress flap is mounted inside the egress door, correct? <br> <br>Looks great, think I'll build one similar for mine for the wintertime, thanks for the idea.
Yes. The egress door is basically a framework for the ingress door, rather than a solid flap. <br> <br>Even though I'd seen doors of this design before and even built a small one, I found working out the particulars a mind-bending exercise. It's very easy to get turned around: the magnetic catch is supposed to face which direction? And then once you've built it, it's all very simple.
<p>Hi there, I love this very much! Is it possible you could take some video of the door in operation, both going out and coming back in?<br><br>How cold does it get where you are? Is this door drafty at all?</p>
<p>I'm sorry to say I don't have video capability. </p><p>Temperatures get down to below zero occasionally. My build of the door isn't drafty as long as it closes properly. As it gets older, it occasionally doesn't completely close. I think a little adjustment and cleaning would take care of that.</p>
<p>The Dog flap only swings one way correct. I don't see how it could swing both ways.</p>
<p>The assembly is one door inside the other. When pushed one way, the outer door, which contains he inner door moves. When pushed the other way, the outer stays in place and the inner moves. Great idea.</p>
<p>This is awesome! I was just lamenting at the price of dog doors from the store, and their inability to really seal well. My parents installed two store bought doors, one on the inside, and one on the outside, and that works well, but is a very expensive solution! <br>My wife and i just got a dog and moved into our first house, and I will definitely be building a door similar to this!</p>
<p>very good project and very good explained</p>
I am going to build one similar. I think I will use old projection t.v. protective plastic for the door. Way too much to buy a commercial door in my cheapskate opinion. Thanks for the inspiration.
great idea, gwylan... my dog wants to go out at least 50 times a day, literally (part wolf, i think). i have a sliding glass door in the kitchen, so during the summer i use one of those magnetic screen thingies... i love it! <br> <br>any chance that you might conjure up a plan for that second flap? i can't put it into my mind how it's built. <br> <br>i've got to do something for this winter.
I'm guessing you mean the inner flap? Unfortunately I didn't take any pictures before adding the duck tape. It is, essentially, just a rectangle of multiwalled plastic, with the rounded edge at the top. The notches in the top corners are to allow space for the eyebolts that hold the hinge pin (long dowel). The dowel runs through the top channel of the multiwalled plastic. <br> <br>If you don't have a handy piece of multiwalled plastic, a similarly sized piece of plywood or, say, Lexan would do, but you'd need to use regular hinges. <br> <br>Any clearer?
Very clever project :)

About This Instructable




Bio: I live on a small homestead in western New Mexico, in a small light-straw-clay house I built with much help from friends. My spare time ... More »
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