A kangaroo helped to build it.
And now, through the aid of a wonderful Feshin’ family who actually used this approach, we have pictures of the process!
The dance floor is constructed of plywood, lumber cross-braces and closed cell foam.
Top Layer: 1/2 inch plywood or particle board in 4x8 feet sheets.
Middle Layer: 1" x 2" cross braces (1" x 4" cross braces where plywood sheets overlap)
Bottom Layer: 1/2" closed cell foam strips (Use the foam bedding rolls available from camping or surplus stores)
The materials listed above are fairly light-weight and offer extraordinary stability and shock protection. In lieu of the foam, a full carpet or carpet padding offers some shock protection, but not to the same degree as the foam. In either case, a lattice system is still recommended for consistency and stability.
If multiple dancers or large kangaroos are using the floor, you may want to consider heavier grade lumber or plywood.
Additional Supplies:
- Screws and screwdriver (or better yet, a drill with a screwdriver chuck)
- Construction-style wood glue and plastic/foam glue tubes
- Caulking Gun
- Clamps, tape measure, and various and sundry other dance floor construction paraphernalia (use your imagination)
- Harp Lager (estimate two beers for each full plywood sheet if two adults are building the dance floor)
- Age-appropriate beverage of choice for younger assistants
Size:
Use full sheets of plywood in whatever geometrical pattern is appropriate for your basement size and daughter’s dancing dreams (two, three, four or more whole sheets.) It eliminates cutting and keeps the measurement math for the lattice and necessary supplies to a third or fourth grade level. Besides, a kangaroo with a power saw is not a pretty sight.
Create a support lattice with 16 inch by 16 inch squares using the 1" lumber. For the most part, you’ll use 1"x 2" lumber to make the lattices but on the edges, where you are joining two plywood sheets, overlap the sheets with the 1”x 4” lumber.
Attach the lattice to the bottom of the plywood using screws, standard lumber adhesive and caulking guns. I highly recommend the screw/glue combo as it makes for a very stable floor. In addition, after a few beers, glue-squirting caulking guns have immeasurable entertainment value.
Feis dad and daughter assembling the support lattice
Cut the foam pads into long, 1.5 inch strips and glue them to the bottom of the lattice using the same caulking gun with a different glue appropriate for plastic and foam. Build the floor in 4x8 foot sections and assemble them together all at once. Make sure you allow the glue to dry for at least 24 hours prior to using (you also want to let your dance area air out a bit too, or your dancer may be a little light on her feet from glue fumes).
4 x 8 sheet of particle board with lattice and foam (note areas of overlap) 
Pre-assembled sheets are laid down and overlapped 
Finished dance floor. Note the extra bonus of the mirror wall!
One more thing, don't ever, ever, let the kangaroo put a beer can in the caulking gun!
Trust me on that one!
