Okay, first of all, true confessions: I love my cat, but I don't like the fact that the kitty litter box is hard to locate in a place where we don't have to experience it. As often as it gets cleaned, even using good kitty litter, it still smells and doesn't look that great. Also, I concede that either 1. I don't have the patience or skill in behavior modification or 2. my cat's will is simply stronger than my own to train her to use the "people" toilet. That said, I love my cat "Moosette" aka Moose or just "fuzzball", as a member of my family, and wanted to give her a private area of the house to take care of her contemplative moments and relieve herself in a quiet, and dignified manner. Since I'm committed to keeping my cat indoors, for her health and the well being of wildlife nearby, this was my solution. So, I put a Pet Access door in the wall between my entry-way and the garage, and enclosed the litter box in a screened enclosure. Any cat owner will agree that most cats appreciate this considerate treatment to permit them to concentrate on more important cat duties, like sleeping all day.

I made this simple kitty privy a few years ago, and feel sort of embarrassed even posting it as an instructable - like maybe it should go in as a "Hints From Heloise", but a couple of people have said that it might be helpful to others, so here you go!

Step 1: Tools and Materials

The tools you'll need:

Tape measure
Utility knife
Sheetrock saw
Stud finder

Materials:

Pet door (available from any pet store)
Thin sheet metal flashing to make a tube for a passageway through the wall
Wood for framing the enclosure in the garage
the particular enclosure you make will dictate your needs
Screen for the enclosure
Hinges and a catch to allow opening of the enclosure for cleaning

Step 2: Planning Your Construction

This is obviously a step that will require you to think through where the appropriate hole needs to be made. In my case, I drew a sketch of the wall into the garage from above, a "plan" view, and also an "elevation" view to show where I might build an enclosure for the kitty litter box. Since it's important to have the enclosure ventilated, I wanted to surround it with wire. Also, my cat is very attached to me, and likes to keep an eye on me when I'm out in my garage shop, so I made it big enough that she can sit and watch me when I'm working on projects.

You'll want to follow the instructions for your particular pet door, and use the template that's provided with it to mark the layout for cutting through your sheetrock. Typically, the wall going through to a garage is framed with 2" X 4" (or possibly 2" X 6" ) studs, 16" on center, leaving a 14 1/2" opening between them. Use the stud finder to locate these studs and then drill a small hole to verify that you've located the hole with enough clearance to fit the pet door. I then used a long drill bit to go through to the other side to verify where it would hit the wall in the garage. Keep in mind that if you have any electrical outlets on a wall, that the wiring is likely to be fished through holes in the studs not too far above the floor level and you will want to be very careful not to hit a live wire!

Once you've verified that you have a good place to build the garage enclosure, make a sketch of what will be needed for materials to support it with a framework and a plywood floor. In my case, I made the enclosure 20" deep (from the wall into the garage) and 36" wide. The platform is about 16" from the garage floor to accommodate the opening in the house at the level of the floor. You will of course want to plan for a means to open the enclosure for getting to the litter box for cleaning.

Step 3: Construction

Now it's time to make your cuts in the sheet rock. Depending on the way your particular wall framing was built, it's most likely that you will be able to cut down to about 1 1/2" above the floor to the "bottom plate" of the framing. Using the template for the pet door, I raised it about 3" to allow my kitty to get through more easily.

Verify your layout once more to make sure you haven't made any errors, and then make the cut in the sheet rock. Remember the old adage, "measure twice, and cut once"!

I inserted a piece of metal flashing that I got from the hardware store into the opening, and curved this into a tube shape to make a clean passageway through the wall between the openings.

Construct the enclosure as needed for your particular layout in your garage.

Step 4: Put It to Use!

The pet door that I got has a swinging plastic door with a magnet that secures it in a closed position. It took a little bit of coaxing to get my cat to go through it, but to make her feel safe, we taped the door open for a while so she wouldn't feel threatened by it. Once she got used to it, we let the door close and she realized that she could just push against it to get through whenever she wanted.