With the help of my wife, sister, and brother-in-law, yesterday I started my sprung floor.
We put in a solid 6 hours or so, and the result looks pretty nice so far. The first layer of OSB is glued to the foam so technically I have 4.5 independent 4’x8′ sprung floors. Since the saw kept dying on us we weren’t able to cut the frame or the top layer of OSB, but once those are cut we’ll be on to just screwing the top layer on to make it one floor and framing it in.
I’m pretty excited. My wife was a bit shocked when we put the first layer together about how big 12’x12′ (3.66m x 3.66m) really is. 144 ft^2 (13.378 m^2) is just about one and a half times bigger than the base Gracie Garage requirement. It’s about one fourth of the space we use in judo for 20+ people. It’s just about the minimum space for me and one other person to have a healthy roll, but still too small to safely consider judo practice. I’m glad I chose smooth over tatami for that reason – it’s a sprung floor so if we do throws it’s super nice, but it’s not big enough to do anything active except ground work.