Here are a couple of house plans that were designed with sports courts in them. One of the main things to consider when buildig a sports court is to make sure that the perimeter walls are insulated well. It may be wise to use soundboard as well so that the noises of the gymn don't go throughout the rest of the home. I beleive both of these had a ceiling height of around 18'. the first basically had a two story basement on one half of the home because the lot it was designed for had a ton of slope side to side. The second house plan had a suspended slab in the garage and the court was beneath the garage - more expensive I think, no windows and it echoed pretty bad because it was all concrete inside there. Basically a great big cave.