Expert: Dan Griffin - 12/29/2007

Question
I am building a home theater in a basement  ...  want to build a platform to raise the floor in half of the room.  Any special requiremetns  ..  was planning on using presure treated 2X6's on the concrete and then putting 2X8's on top and then 5/8 underlayment.  Have had NO issues with water  ... although a basement it is effectively a walkout.

Answer
Raising the floor on a 2x framework would be quite normal.  It is a good idea to use treated lumber.  Hardwood floor sleepers are often installed on small resilient isolation pads  This is done for sound, squeaks, and to provide an air chamber that provides flex in the floor for running, dancing, or aerobics.

I don't know why you would cap the framework with 2x material.  Unless this is something quite unusual, a single layer of 3/4 ply glued with construction adhesive and nailed or screwed should be quite adequate.  If you want extra stiffness, you might look at 1 1/8 tongue and groove decking.  It is available in wafer board and in plywood and would be the typical product  used in new construction rather than multiple layers.  Again, I would use glue and thorns.