converting part of the garage into an office

[Von Bickley]

Unlikely that 18 years ago a vapor barrier would have been put under a garage floor. Typically they just pour the slab over whatever happens to be there without doing any smoothing even. In your progress picture, is the non PT wood off the floor and just nailed or screwed to the pieces of PT? Here in the Northwest, that construction would not fly.

I would have used all PT for the floor system. I don't think it would have cost much more.

[Stew Hagerty]

As a former General Contractor, this is how it should be done. If it even has one, the vapor barrier under the slab ALWAYS has holes so using a second one is not only perfectly fine, but I would not build without using one. You absolutely need to use PT lumber against the concrete. While you don't need to, I would place pieces of rigid foam between the sleepers. Roll out a continuous vapor barrier between the sleepers and the plywood. Use T&G Ply for the subfloor, add a piece of Luan on top if you are going to use tile of vinyl.

[Larry Browning]

Unlikely that 18 years ago a vapor barrier would have been put under a garage floor. Typically they just pour the slab over whatever happens to be there without doing any smoothing even. In your progress picture, is the non PT wood off the floor and just nailed or screwed to the pieces of PT? Here in the Northwest, that construction would not fly.

Yes the non PT is off the floor. Here in Arkansas we have mild winters and VERY hot summers.

[Larry Browning]

Yes the non PT is off the floor. Here in Arkansas we have mild winters and VERY hot summers.

Well, it's too late now. The floor is down.
No vapor barrier, but at least he used PT against the concrete. I am really not too worried about it. The concrete has never sweated or been wet in the past 18 years. Our winters are pretty mild here, I think I can count on one hand the number of times it has gotten below zero since we moved here 30 years ago. We didn't get any snow this year. Most years we might get 2 or 3 snows that are more than a dusting.