Plywood Subflooring on Slab Foundation

I have a slab foundation levitt home. I pulled off 4 layers of flooring and got down to the bare slab. I want to put a subflooring of 1/4" plywood under vinyl tiles.what's the best way to do this without nailing and also having some kind of vapor barrier between the concrete and the plywood ???

You can use mastic to glue the plywood down. (It will never come up for the next time though) Check where you buy it, but I think you can put a coat down, put the plastic down, and put down another coat and lay the plywood on top of that.

The cost is more, but if you go with ceramic tile they will last much longer than vinyl and you don't need to put down the plywood, they will go right on the slab.>

Evening Slab Floor

I'm in the process of renovating my downstairs bathroom and the slab floor was uneven. I purchased some "self-leveling" compound (cement) and the product didn't perform as advertised. Now I'm still left with an uneven floor. I want to lay some ceramic tiles (12x12) and was wondering just how even the floor has to be. Can I add more mastic in order to fill in these gaps? The floor is not too bad (maybe 1/4" fluctuation at the most).

Yes you can buy a thick bed mortar which will allow for your 1/4 inch fluctuations. Even thin set mortar will allow for some unevenness.  Explain what you need when you buy the mortar and tile and they should recommend the correct mortar.

Adding Height to Room

I am looking into options for expanding a family room into a 25 x 25 garage. The framing for the garage walls rests on a concrete foundation approximately 6 to 8 inches above the concrete garage floor. The garage framing is of 2 x 8 construction.

If I use 2 X 10 or 2 X 12 floor joists and place them on top of the existing concrete foundation ledge my ceiling height will be about 7 to maybe 7 and a half feet high, with an underfloor crawl space of 6 to 8 inches for wires/piping etc. I am looking for other options so I can try and achieve as close as possible to an 8 foot ceiling.

Why don't you build the floor right on top of the concrete flooring? If you rest the floor joists right on the cement floor, you can save the height. The joists by no means need to be 2x12's or even 2x10's if they are resting on the cement across their span. In fact they could be 2x4's, just thick enough for you to nail into. Even if you insist on resting the floor the foundation's ledge, you can use 2x4's just support them every 2 feet from below.

Flooring Choices for Slab Foundation

I'm trying to evaluate flooring choices for a house I bought that has a slab foundation. The current carpet is moldy. I have been told a thermal barrier might help prevent mold in the future.  Can we put in hardwood floors? If we do carpet, what type of carpet and pad would be best to prevent future mold problems. Any other suggestions?

I would suggest ceramic tile for your floor and not just because I sell the stuff. If the is moisture coming up through the slab, hardwood would not be a wise choose unless some sort of vapor barrier were installed. Hardwood takes very little moisture from underneath. Prego may also be a good choice. But anything you choose, a vapor barrier is a good idea. Tile adhesive manufacturers make liquid paint on barriers. Check them out.