Subfloor on Concrete

Above or below grade? In general, wood is not recommended on concrete unless there is a vapor barrier, insulation, then the wood. You can use engineered wood floors with just a special vapor barrier.

It's above grade and I thought of a poly sheet as a vapor barrier (Vapor Lock).

I'm trying to minimize increasing the height too much, and I was thinking about 1/4" or 3/8" thick. Are such thicknesses feasible?

TIA

What are you putting on top of the subfloor? 3/8" is not much to nail into for a real hardwood floor. For floating floors, then yes.

I'm stapling 5/16" hardwood floor using 1" staples. I just measured how deep the staple goes at 45=B0 and it requires a subfloor 1/2" thick.

My motivations is that after stapling the hardwood strips upstairs on wood underlayment, I'm concerned that gluing them on concrete is going to be not only more laborious as would increase the waste.

I've found several strips which were a little bent up or sideways and I'm afraid that the glue would allow for such strips, unlike when stapling.

Thoughts?

TIA

You said your staples need 1/2"... I'd want 3/4 to fasten to. You can get T&G 3/4 ply made for the purpose, no sleepers needed but you should use a vapor barrier.

I'd think that 3/4" would be better too. However, the floor would be about 1" higher than the slab, creating a step when it meets other floors, even tiles... I'm split over this, do you have any advice?

Thanks for your help.

I would partially bevel a strip of the wood floor where it meets the tile.

Most of my house is Saltillo tile but my wife wanted 3/4 maple in her office. Tile on slab, wood over 3/4" ply subfloor on slab. The maple is about 3/4" higher than the finished tile surface and I did the beveled strip thing. I *also* placed it so that it overhangs the subfloor by maybe an inch; I then slid tile edges into that void. One doesn't notice the height difference when going from wood to/from tile areas and there is nothing to trip on.