Awhile ago I had decided I needed a cat house so my 2 cats would stop jumping up on the counter and had somewhere to play. I bought a cheap one off of eBay for about $35 and set it up. A few months later it was really showing it's quality (or rather a lack thereof). I tossed it out as it was pretty much unusable and started looking in to a higher quality option. All that I could find that was a decent size and quality were setups that cost a few hundred dollars. I thought to myself "I can make something much better for much cheaper" and so I began this project.
Step 1: What You Need
Old entertainment center (I found one on craigslist for free but others can be found really cheap)
Pack of eye screws
Pack of key rings
A couple of cheap cat toys
Dremel (or other rotary tool)
Hole cutout attachment for rotary tool
Router bit for rotary tool
Tape and a Marker
Step 2: Planning
I started by arranging the shelves where I thought they should go to make it easy for the cats to get to the top. I then measured how "large" the bigger of my to cats was and then added a couple inches to that to figure out how big the holes should be. A 9 inch diameter hole was the perfect size for them to be able to travel through easily.
Next, I measured where the holes would go and marked the center with a marker and some blue masking tape. I had to rearrange some of the shelves to make things fit properly.
I then removed all of the shelves form the outer sections and unscrewed the door shelves from the inside section. I drilled a hole in the center of one of the top holes (with a drill bit in the dremel) Set the hole cutting attachment to cut a 9 inch diameter hole, set the bit depth and cut out a test hole. I sanded the edges and then sat one of my cats on the shelf next to the hole and coerced him through with a treat on the other side. No issues.
Step 3: Cut Out the Holes
Start by putting on your safety glasses, high speed rotary bits + Dense press board = lots of flying dust.
I loaded a drill bit into my dremel and drilled the center holes for all of the remaining cutouts on the entertainment center/cat house. I believe a 1/8" drill bit fit the center point of the cutout tool.
I loaded a wood cutting router bit into the Dremel and set the proper cut depth, set the hole cutout attachment to cut a 9 inch diameter circle, and then set the tool to a pretty high speed. I turned the Dremel on, pressed the tool center into the hole I drilled previously and slowly plunged the router bit into the wood. Going slowly I went clockwise around the circumference of the hole. Go slowly here as attempting to go fast can burn up your router bits and even break them. Sand the edge of the hole to prevent possibly injuring your cats. Repeat this process for the remaining holes.
Step 4: Reassemble and Add Toys
Put all of the shelves back into place. I left the closed in section shelves out to give my cats somewhere to hibernate.
Now decide where you want the dangling toys to go. Drill pilots holes into the wood and screw in the eye screws. Make the toys hangable but tying one end of a piece of paracord to the toys (some toys have loops on them, some require some creativity to hang). Tie the other end of the paracord to one of the key rings and attach one of the clips in the key ring kit to the key ring. Clip the dangling toy to the eye screw loop. Repeat for as many toys as you need.
The clip in the key ring kit makes removing/changing the toys out easier and gives a break point if your cat accidentally gets caught on a toy.
Step 5: Get Approval
Now let your cats play with it. Some may take a little motivation to try it out, some will just go to it on their own.
You can add other accessories to it as you see fit. Beds, small toys and tunnels really help.
Step 6: Think About the Future
This was just a very basic build to get a good cat house made. You can add whatever you want to it.
I have plans to add lighting, cover the front of more shelves (with peep holes so the cats can poke their heads out), put in some heating pads and possibly add an Arduino to control it all.