Now I know that it is not ideally suppose to be done. I have a client that is willing to sign a waiver that states that she understands that this is not the norm and that we are in no way responsible for this. She wants plywood anchored to the concrete and the floor nailed on top. How do I go about anchoring the plywood? Do I use felt paper between the plywood and concrete and concrete and flooring? How thick of a layer on plywood will be needed for the cleats to go in all the way? Any help is greatly appreciated.

Howdy Rhodes, why anchor it? Lots of guys are floating two layers of 3/8 ply or one sheet of 3/4 ply. Myself I'd go with minimum one layer of cold roofing mastic and a sheet of 6 mil under it. I think NOFMA suggested if fastening 3 layers of cold roofing mastic and three 6 mil. Gotta have some sort of vapor retarder under it. Felt is simply not enough.

I also know a guy who uses Bostik MVP under his ply substrate (layed in wet) instead of roofing mastic.

Fastening using tapcom screws, some guys like shootin down. But thats seems like to much work for me. I reccomend gluing engineered

Securing, as well as floating, a wood subfloor over concrete , and nailing down 3/4" Hardwood has been an accepted installation practice for many years.

http://www.installingwoodfloors.com/ins ... ncrete.pdf

I use the Bostitch T-Nailer , makes fastening a breeze. Of coarse there's other ways to go.

Really Howard? Jeez you must have some really soft concrete up there. Those things can't even hold down carpet strip here. Course those were the old duofast ones that came out long ago

Some concrete softer than others ofcoarse, but I've been using the same M111 for well over 20 years, on some darn hard slabs. I do have to put some pretty good pressure down on it to sink nails into harder slabs, or it will bounce you on your butt. Other than that I can rattle off a sheet pretty quick, and I'm overkill on t-nails. I know they have come out with a bunch of guns since that are probably easier to use on the harder slabs, ( or just gain a little muscle or weight... or get a bigger helper ).

We use HILTI quikcon fasteners, its a breeze, although here in Canada you must be licenced to use the tool. The Feds think its a gun, lol.

Hilti Fasteners ! Hilti is excellent, but you guys must have money to burn up there