This article is from the Ballet and Modern Dance FAQ, by Tom Parsons firstname.lastname@example.org with numerous contributions by others.
First, the reason for this question: A hard, unyielding surface
like concrete is a killer. To avoid injuries, you need a resilient floor.
These floors are termed "sprung floors," because the construction makes
the floor springy.
My own opinion is that this is a job best left to professionals.
But for a discussion of ways to make a sprung floor, look at
which is a collection of e-mail messages discussing various aspects of
making, finishing, and maintaining dance floors.