Re: building home dojo, need advice
Zebra mats are good stuff. You might look around on eBay or check with Zebra themselves about used mats. Zebra will often cut a good deal on mats they use as display models or in shows and seminars. That could save you some money.
A built-up subfloor in a basement dojo is probably overkill, and in a basement, I would imagine that ceiling height is already at a minimum. No point in making it even less by building up the floor. You probably won't get much jo or bokken work done with the low ceiling either way.
The 12' x 24' area should be OK for 2 people. Just like any other time, you should be aware of your surroundings, to avoid rolling into the walls.