I have found there to be two main approaches to tower building.

You can start with a main pillar and build out, like a tree, or you can have four corner pillars and build in, like a tower.

I prefer the latter, as it allows for really good stability (if you know you are going to have four cats running up and down it, for instance, you need stability) and it allows you to have larger platform at the highest elevation.

I plan the basic footprint I want, such as 2X3 feet, then plan out where the levels should be placed. Even though you have a kitten, you have to plan for a full size cat, so that he won’t grow out of it. Imagine floors with different spots (never above one another) cut out so that he can comfortably move from level to level, usually space at least a foot apart, if not 16-18 inches. I have found that they really like to run at the tower and climb/run all the way to the top really quickly when playing or being hyper. If you can plan the levels and cut outs to allow for him to easily do this, he will be even happier.

Then you can also plan for various, uh, porches (?), where a floor will extend past the support pillars. This can vary depending on where you are putting the tower, and how high it goes. The one I build in our bedroom has a massive top floor that extends out for maximum perches, but it’s above our heads, so it isn’t in the way.

The main pillars can be 2X4’s, or you can go high class and have 4X4’s. Or mix the two. Floors are supported by cross beams attached to the pillars, which can be 2X2’s or 1X2’s. The floors are plywood, I can’t remember if I used 1/2 inch or not, but 3/4 inch is unnecessarily thick. Make sure the wood isn’t treated with anything. Left over wood from porches is usually treated with chemicals and such is no good.

I like to put a little trim around the outside edges of the floors, just a little ridge of something, like a 1X1 or something even smaller, as they seem to enjoy leaning against it when lounging, and I think it allows them to know where the edge is when they are sleeping and rolling about.

So you have levels, cut to various sizes, pillars and supports all planned out. I carpet the individual levels after cutting them out and attaching the trim, before I assemble the whole thing. Carpeting you are going to just have to try. It can be pretty tough. It seemed as though I took a different approach every time, and it always looked pretty good. You can carpet the pillars, or wrap with sisal, or leave them bare, depending on the look you want. The carpet will be the most expensive part of the whole thing. Don’t bother getting padding, it’s unnecessary, and if it’s already attached to the carpet, it will make doing corners really tough. I attach the carpet with a staple gun. Use an electric one, it’s alot of stapling.

Keep the extra carpet, so you can replace as necessary due to wear and tear.

I would go to the local pet store and look at the $350 models and take structural ideas from them. Then plan out what you think you want and price all the individual parts, the wood, the square footing of carpet, etc. I don’t know if it would be really worth the time and effort unless you are doing a very individual design. The one in our bedroom (in the picture)uses alot of space over a radiator that is never turned on.

I figure if you are going to do it yourself, invest the time and money, you might as well go crazy.