Installing a Sash Window Cat Door with Vinyl WIndows

Posted by Jon Mortensen on Oct 11th 2016

Simple Cat and Dog Door Installations In Older Wood or Aluminum Sash Windows

Sash window pet doors are usually used for cats, but can also work for dogs if there is a vertical sliding window mounted close to the ground in your home. Doggy door or kitty window, the installation in older windows is usually very very easy.

Simply raise the window, set the pet door in, adjust the width then lock the adjusters in place. All that is left is to apply the peel and stick weather strips. There is one roll of foam weather strip that is to be used on the top of the pet door where the window closes down on it. The higher end pet doors include enough to use weather strips on the bottom as well. The other weather strip is a soft vinyl piece with double sided tape on on end. When your window is closed, the frames overlap in the center and there is a fuzzy seal in between. With the window open to accept the pet door, that seal is broken. The vinyl weather strip can be applied on top of the inside window facing out to hit the glass on the outside window, or on the bottom of the outside window with the seal facing in to hit the inside window. It should be installed so that the edge of the seal just barely touches the glass on the other side. It may look like a squeegee blade, but we don't want to try and clean the window on the other side, as that makes it very difficult to move the window.

Vinyl and Double Hung Window Kitty and Doggy Door Installations Can Be More Difficult

The other half of the time, they require a little more work. The issues seem to revolve around double hung vinyl windows. These windows can swing down so that the outside glass can be cleaned without going to the outside of the house. The problem with these windows is that the pet doors often times don't fit into the tracks. While the window frame itself may be 1" or 1 1/4" thick, the slot in the side of the window track can be anywhere from 3/8" to 3/4" wide, which won't be wide enough for any of the pet doors to install into.

How Do You Lock the Window With a Sash Pet Door Installed?

Before we address the narrow track issue, let's deal with the window lock. No pet door manufacturer provides a lock for the window with this kind of door. The reason for this is that there are many different kinds of window frames and tracks, and anything provided would likely not work for everyone, so they just leave it up to you to figure out. The basic idea here is that if you can't move the window, you can't get the pet door out. The pet door is effectively trapped, as it is plugged into the track on the sides and the bottom. A couple simple solutions for locking the window are: pin locks, a screw in the track right above the window frame, screwing both window frames together with an angle bracket, and clamp on track locks.

Pin Locks

There are various types of pin locks and you can find them at your local hardware store, all are very inexpensive, should be less than $10 at the time of this writing. The kind that I like best is usually 2 1/2" to 3" long, and it locks the two window frames together where they overlap. This means that you drill a hole all the way through the inside window frame, and into the outside window from, but not all the way through that side. The steel pin is inserted into the hole, and that locks everything together. The pin usually comes with a chain and there is also a little hanger that bolts to the window, so that when you unlock the pin you don't lose it, and you can set it on the hanger so that it isn't dangling from the chain.

Screw in the Track

Another solution is to put a screw into the track of the window, so that if someone tries to lift the window, the frame hits the head of the screw. This is really easy to do on older window frames, and can be done inside the track, so that if you take the screw out, the hole for it is unlikely to be seen. On the flip down vinyl windows this method usually doesn't work. Sometimes it is possible to put a screw into the face of the window track, although that leaves a (small) visible hole if the pet door is removed later on. A bit of caulk might suffice to hide the screw hole.

Angle Brackets

A third solution is to use an angle bracket to attach the window frames together. Again, this leaves visible holes in both frames, but is a very secure option, similar to the pin lock.

Clamp On Track Locks

Lastly, a simple clamp on lock that attaches to the track above the window will also suffice if it is not a double hung window where both panes of glass move.

Attaching a Sash Window Pet Door to a Frame With A Narrow Track

What we need is a way to attach the pet door to a track that is narrow, and we have two easy solutions: You can use angle brackets to attach the pet door to the window frame. Alternatively, a "bridge" piece that is narrow enough to fit into the window track can be attached to the pet door.

Angle Brackets - Again

If the pet door is too wide to fit into the narrow slot in a vinyl window frame, the pet door can be attached with angle brackets. I went to Home Depot and found them listed as "corner braces" near the door and shelf hardware. This is simply a flat piece of metal bent at a 90 degree angle with a hole in each side. One side gets screwed to the pet door, the other end gets screwed to the window track. Install one at each corner of the pet door frame, and screw to the window frame on the other side. This is a really simple way to anchor the pet door in place.

Bridging The Gap

The spring loaded end of the Fast Sash and Thermo Sash pet doors have an H shape at the end, where one half of the H overlaps the pet door, and the other half is intended to slide into the track. The inside of that H shape is about 3/4" wide. If your track is only 1/2" wide, you can use a 1/2" x 2" piece of wood or metal and plug it into the end of the pet door on one side, and the window track on the other. This piece can be screwed in if you like, but it probably isn't necessary.

Bridging a Thermo Sash 3e

The Thermo Sash 3e has one spring loaded end, and the other is just flat frame. There is a way to install it without using angle brackets, even if it won't plug into the narrow track on the flat end. The solution here is to use the bridge piece solution, but to screw the bridge into the end of the pet door. You'll want a short bridge in this case, so that the pet door frame butts up to the window frame and the bridge doesn't show. Using a suitable piece of wood or metal, drill holes into the end of the pet door and screw the bridge piece to the end. On the spring loaded end, you can use the bridge piece as previously described.

Spring Loaded Knob Doesn't Fit Inside the Track

Occasionally the lock down knob on a spring loaded cat door won't physically fit inside the track at the bottom, because the track wall is too tall, or the knob sticks out too far, depending on whose side you're on. ;) The solution here is to remove the knob. The knobs cannot just be pulled straight out of the frame; there is a trick to it. The spring load post has to be compressed to just the right spot so that a groove on the post lines up correctly. When you get this right, the knob will pull out very easily. If you're pulling hard, stop. It should come out with very little force. In order to compress the spring load to the correct position, we need to first remove the H shaped adjuster. This is held on with two phillips head screws which you can access from the end of the door. Simply remove the two screws and pull the end off. Now you will have 2 chrome posts sticking out of the end of the pet door. Put the screw back into the bottom post just a few threads, and then push on the screw to compress to the right position to pull the knob off. Why use the screw? In some cases the post has to be pushed in past flush in order to line up the notch in the post with the knob, so simply pushing down in the post with your finger won't compress it far enough.