drywall underlayment?

Hi all, I'm building a rehearsal room on the second floor of my garage. Right now the subfloor consists of 3/4" T&G plywood. I was thinking about adding a layer of 1/2" sheetrock on top of the plywood for a bit of extra mass, followed by foam and laminate flooring. Is it unwise to use drywall on the floor as an underlayment? Is the drywall durable enough to withstand the kind of abuse that it would encounter over time? I'm looking for an alternative to cutting and securing strips of drywall between the 14" I-beams underneath the plywood. Any ideas? Thanks, C

Not sure, but I would think drywall would break up and cause problems for you later. I'd go with another layer of plywood. Of course, I defer to someone with real knowledge about such things... Anyone? - Andy

I have done some renovation to a 25 year old studio. There were two layers of 5/8" in the floor sandwich. They had definately started to break down. In one high traffic area it was basicly just chunks of gypsum. John Katsafanas

Use cement board. Its as dense if not more so than gypsum and is meant for foot traffic under tile. 2 layers should work. Check your weight requirements on those floors first. Hope this helps I edited the large part for emphasis - Steve