Benefits of High Aspect Ratio Pet Door Flaps

Low Aspect Ratios are Bad!

Low Aspect Ratio - A Pervasive Problem

Most pet owners are properly concerned that the pet door opening be an appropriate fit for the dog not only when he's a young, agile guy but when he's toward the end of his life and less agile, possibly arthritic or injured in some way. Understandably, this question can be a hard one to answer.

Many pet door manufacturers have no clue themselves!

They will commonly say something like "cats to 15 lbs" or "dogs to 150 lbs". This is nonsense and the worst kind of dis-service to the potential customer trying to make a good decision. It is self-evident, for example, that a standard poodle, tall and slim, will best use a very different pet door from the bulkier and much shorter lab. Every dimension matters: The height and width of the flap and also, just as importantly, the "step-over".dimension.

Here's a method that will lead you to a correct answer

Put the top of the flap opening at your dogs withers (top of his shoulders). Having the top of the flap an inch or so above the withers won't matter much to the dog but will extend the otherwise short life of the typical vinyl flap you're probably working with.

With the top of the flap in the proper position, the bottom should be as low to the floor as you can get it! No "step-over" dimension is too short. Lower is always better.

Any rise dimension taller than 30% of your pets height for most dogs, and less for particularly short-legged or deep-chested dogs, is going to be too high to start with and way too high when he's older, less agile and possibly arthritic or injured.

Then call him through an open doorway set at just the proper width in your judgement (it is somewhat subjective and it's your call) and measure that width. That is the absolute minimum with of the flap you should buy.

If you do this a few times with a few different dogs here's what you'll find

First, the minimum width will turn out to be much more narrow than your "guess-timate". This is an optical illusion that we're all prone to and which results in the sale of bigger than necessary dog doors all the time. The dog or cat just isn't as wide as you think he is (unless you're one of the very few I've met over the years that really can eye-ball an accurate width for a pet. Some people have perfect pitch also. But I don't and you, dear reader, probably don't either. Measure the doorway!)

Next you'll find that when you go shopping for a flap that's at least that width, the height of the flap is going to be much less than you'd like.

Why is this??

Most pet doors for sale today have a relatively low 'aspect ratio'. That is to say, they are not very tall for their width. For example, my 75 lb lab stands 22" at the withers and needs a minimum of a 9 1/2" width. The very commonly found 10:" x 15" sized flap is not very satisfactory because if I mount the top of the opening at 22" (her withers), then the bottom will be 7" off the floor (22"-15").

She's fine with that today at age 11, but she's nearing the end of her life and I want her to enjoy her dog door for as long as possible. The flap she actually has now is the Endura Flap at 10" wide by 19" tall and the rise dimension is 3". Much, much better!

The above example represents the situation most commonly found. Dogs are much more often tall and slim rather than short and wide. But most pet doors (not all) are more appropriate for the short-wide type.

Security Concerns

There's frequently another, less obvious problem with these low aspect ratio flaps and that is security. Especially for dogs around 20-60 lbs--which is a lot of dogs--there is a security issue. A great many dog owners will look a typical 8" x 11" flap and say "width is ok but I need more height". Then they look at a the next size up--frequently 10" x 15"--and see that the height is now ok but the additional width that they don't need has made the pet door large enough for a person to crawl through!!

The Endura Flap #8 is 8" wide by 15" tall. Not wide enough for most people to climb through but tall enough for many dogs that are too tall for the typical 'medium' size.

Pet Door Mounting Height

Aspect Ratio Problems Continued

When you mount a pet door, the top of the flap should be at least as high as the top of the dogs shoulder (the 'withers'). It doesn't do a lot to make it much taller than that (unless you have a typical vinyl flap where more height will prolong the life of the flap).

So a higher aspect ratio flap really means that the bottom of the pet door can be lower to the ground!

This height above the ground dimension is called "step-over" and lower is better other things being equal.

Of course, if you do need more width, you get it by getting a larger size. Chances are, though, if you need a wider door, you'll want an even taller one as well and that's what you get with the Endura Flap™.

Benefits of High Aspect Ratio