[glennv]

I've installed hardwoods before but always on a wood sub-floor. Our family room is an addition which is a slab. I know I need to put a wood sub-floor and want to know the best way to secure it down. Also. I do with 3/4" plywood right?

[Willys2TJ]

I don't think you HAVE to put down a wood subfloor but you definitely should put down a vapor barrier first no matter what you put down.

I've seen the pre-finished T+G wood floors installed directly on the vapor barrier. Its a floating floor (not nailed down) but you can't tell when you walk on it, assuming the concrete is level.

If its an old slab with cracks or slightly un-level, you might want to use a plywood subfloor first over the vapor barrier.

You can also seal the concrete first to help prevent moisture problems.

[afran]

I am not even sure you need a vapor barrier. My house that we just sold had wood floors that were just glued "liquid nails type of stuff" to the concrete. The only reason I know this is when we were moving, the movers scraped a few planks and we had to replace them. I hired a sub to come out and he told me that was standard, at least here in central tx, to just glue to the slab. hope this helps.

[sitdwnandhngon]

Hopefully before they poured the slab they put down a vapor barrier. It's pretty standard on the inside of houses and basements to prevent moisture and radon and such.

If you never have problems with moisture you can probably just glue down a subfloor. Or like was said earlier you can seal it first for extra protection.

[NEVERSWEAT]

Originally Posted by glennv

I've installed hardwoods before but always on a wood sub-floor. Our family room is an addition which is a slab. I know I need to put a wood sub-floor and want to know the best way to secure it down. Also. I do with 3/4" plywood right?

Glenn,
I put down beveled edge Bruce toasted oak on a concrete floor. I had the advantage of cutting coving out and going over a lenolium flooring. If you do not have that ( which if I read here and you do not) get something like a light felt/paper product designed for that purpose. There are several reasons which I can quote from why you need the vapor barrier ,two off the top of my head, being a moister concern and the hollow sound coming from the lack of a secondary means of sound proofing the sub-surface.
Lime has a tendency to come up through the concrete in the form of a fine dust with plenty of moisture in it and it will damage your floor albiet no barrier. My advice based on the best minds in the business IMO..get a barrier.

[coldwater]

problem with concrete is, that while it cures, it never dries, even with a vapor barrier installed under the slab. Concrete will forever absorb moisture and then release it into the surrounding surfaces. I typically will not do an install over concrete because of callback problems. If you must do it, seal the floor with a proper sealer, followed by a vapor barrier, then lay out pt 2x4's as a base to lay your sub floor over before you begin laying the finished floor. As an added sound deadner, and small r value. you can add blue board foundation type ins board between the 2x4's before installing underlayment.

[vadslram]

Make sure you have a vapor barrier!
You can stick it down but why? I set mine as a floating floor. I glued the planks together but not down. It lets the floor breathe and move.

[Chris]

I have installed several in the mountains here in CA and I use plastic sheeting for a vapor barrier and then 3/4" Marine grade OSB T&G for the subfloor and hold that down with 2" concrete Screws predrilled. Then you can install the floor like you would on wood. I think with a floating wood floor that is a laminate you would not have to go through this trouble.