My cat Uli lost his hearing earlier this year. His eyes and nose remain sharp, though, and there’s plenty for a cat to see and smell from our front-porch windows. I made him a simple catio.
Catios are enclosures that give indoor cats safe access to the outdoors, usually via a window. They’re having a cultural moment, as The New York Times reported in September. Elaborate models could double as chicken coops; basic versions are no bigger than a window air-conditioner.
If you don’t have a cat, I hope you’ll still find the project useful. The catio I made is a just a box, and a box is one of the atomic units of carpentry. If you can make one well, you can make a lot of other useful things. Individually, the techniques lend themselves to many D.I.Y. projects.
This catio should only be installed on a ground floor. Catios on higher floors should be braced against the exterior wall or fully anchored to the window studs, and I don’t go into those methods here.
Tools and Materials
You’ll need a manual miter saw, drill, ¼-inch drill bit, tape measure, square, utility knife or pocketknife, polyurethane wood glue, and hammer. I used regular wood glue on my dowel joints, but the polyurethane glue is fine for them too. The other items in the photo are nice-to-haves but not required.
If you don’t own long carpenters’ clamps, you can use long elastic bands or temporarily screw the wood joints together when gluing.
I recommend buying a brad-point drill bit. The needle tip will help you precisely center it on your marks. Standard bits tend to wander.
As for materials, I used one-by-two pine boards for the catio frame, one-by-threes for the sills that catch the window frame, and half-inch plywood (technically, 15/32nds) for the floor and roof. Look for so-called project panels: These 2-foot by 4-foot sheets of plywood are a fourth the size and cost of standard sheets. If you can, have the store cut them to size for you.
Any quarter-inch hardwood dowels will work fine. I used 1 ¼-inch deck screws to mount the plywood to the frame, and covered the sides with stainless-steel window screen. If you don’t have a staple gun, you can use tacks to hold it on. Lastly, I used 1-inch steel corner braces to attach the catio to the windowsill.
Step 1: Measure and sketch.
A catio has to fit through the narrowest part of the window it goes in. When measuring, don’t overlook the exterior side of the window. Bug-screen rails, for example, may slightly protrude past the window frame.
Make your catio ¼ to ⅜ of an inch narrower than your measurement, to give a little wiggle room during installation. The height and depth of the catio are up to you, but ensure that your window can open far enough to admit it. Take the combined thickness of the plywood floor and roof into account.
Sketch your plan and mark down the dimensions of each frame piece. Be alert to the fact that most lumber in the United States is sold at nominal, not true dimensional, size. A standard one-by-two board is actually ¾ by 1 ½ inches. A standard one-by-three is three-quarters of an inch by 2 ½ inches.
Step 2: Make the frame pieces.
Mark and cut your frame pieces one by one, using the tape measure and square. Saws remove a strip of wood the width of their teeth — a dimension known as the kerf — so if you mark out all your pieces at once along a single board, they’ll wind up at slightly different lengths after you cut them.
Whether you use a Western or Japanese saw, your accuracy will improve if you use a sharp blade, rather than a pencil, to mark the cut lines. This creates a physical guide called a knife wall for the saw teeth to follow.
A common technique for sawing straight and square, and the one I use, is to begin at one corner of the board with your saw tilted at a 45-degree angle to it. In this way you can make a cut that simultaneously follows the knife wall across the top and down the side.
Step 3: Glue and dowel the frames.
Build the square end frames first. Before gluing, dry-fit them to make sure everything lines up. To put them together, you’ll first glue each joint, then drill through and dowel each joint for rigidity and strength.
After the glue dries, trim the dowels flush to the frames, then attach the side rails to the frames with polyurethane glue. These joints won’t get doweled; the plywood top and bottom will lock them in place.
We’re using glue and dowels for the side frames because we’re dealing with end grain. Were you to screw into the end of a board, the screw threads would sever the long fibers that give the wood its strength. A nail would simply push the long fibers aside, giving the nail little grip. The result in both cases would be a weak joint. Gluing and doweling locks end-grain joints tightly together.
Polyurethane glue expands as it cures, filling small gaps and penetrating the wood pores. I used wood glue for my dowels because it doesn’t expand, which can cause the wood to split. If you use polyurethane glue for your dowels, only apply a very thin coat.
It helps to add some grooves to your dowels, to give the liquid glue somewhere to go when the dowels are hammered in. Scraping them lengthwise with the teeth of a hacksaw blade does the trick.
Step 4: Finish and install.
The rest is straightforward. Screw your plywood pieces to the top and bottom of the catio, then screw lengths of two-by-three along the top and bottom rails so that they extend above and below the plywood surfaces by half an inch or so. These overhangs will brace the catio against the window frame.
Staple or tack the window screen around the sides and front of the catio, then place it in the window and attach it to the windowsill using the corner braces. For extra security, use a length of scrap wood as a window stop. Wedged into the window track, a stop prevents the window from accidentally opening and allowing the catio to tilt outward. (In order to close your window you will have to remove the entire catio setup, just as you would a window air- conditioner.)
Your work is done. Whether it pays off is entirely in your cat’s hands — plus ça change — though a few treats and a pinch of catnip were all it took for Uli to buy in.
About The Author
