How to unsqueak my basement subfloor

[singerdancer]

I am having my basement renovated after a flood. We had the basement waterproofed with drainage tile and 2 sumps with a backup system. On top of the concrete floor we have a layer of Karnak mastic, a layer of tar paper, another layer of mastic and plastic sheeting. On top of that are 2 x 4 sleepers that are not screwed to the concrete. My husband feared that would compromise the waterproofing of the floor so he asked the contractor to just lay down the sleepers and attach the 3/4" exterior plywood to that, which they did with nails. The floor has some major squeaking problems. The contractor was going to use a foam sealant manufactured by Hilti which he was going to spray under the subflooring. When I called the manufacturer they said it was not designed for that purpose and would not work. They described it as a kind of styrofoam when dry that would compress. The product expert said he would have used construction plywood adhesive between the sleepers and plywood. We are trying to find a solution to the problem that does not involve screwing the plywood to the concrete floor.

Any ideas?

[TJ1962]

This is difficult to advise after the fact. I would have suggested a mold resistant foam cushioning under the flooring. With a floating floor liquid nails and spacing could dictate noise. A spray foam may work after the fact.