Leveling concrete floor for hardwood

[p8ntblr]

What do you guys recommend for leveling an uneven concrete floor to prepare it for hardwood flooring? I'm thinking about buying hardwood flooring cheap from someone ended up not using it at his house and is moving. Will any wood flooring work over concrete ? If not, how can I tell if the one I'm thinking about getting will work? Can I put glue a plywood sub floor if it's not a floating floor?

I'll post some pics of the flooring when I get home. Sorry for all the questions.

[jackellis]

I can't help you but I'm interested in the answer. At some point I'm gonna have a real shop and have been wondering myself whether and how to put wood over a concrete floor.

[crokett]

What does 'uneven' mean? Does that mean not level or cracked/high/low spots or both? If it is fairly smooth but not level you can add treated sleepers then shim your subfloor to level. If it is high/low spots you can get a self-leveling compound. I used a product called UltraTop from a company called Mapei. A little pricey but very easy to use and it gave me great results.

[p8ntblr]

What does 'uneven' mean? Does that mean not level or cracked/high/low spots or both? If it is fairly smooth but not level you can add treated sleepers then shim your subfloor to level.

If fairly smooth but there is a slow spot along the side of one wall. Here's a pic of the wood floor. I decided to get it and if I can't use it I figure I can give it to my brother. Besides it only costs $50. Do will I need to put a layer of plywood under it as a sub floor. Or can I float it over the concrete? First pic is the bottom part of floor 2nd is top.

[crokett]

Depends on how low the low spot is. Mfgr will spec the tolerance and whether you can float over concrete. From the pic it looks like the edges are quick-lock and not nail down? I've not seen a tolerance more than 1/8" for low/high spots. If that is the only problem area you can get a self-leveling compound in there and feather it out to fill the low spots. What I posted earlier is more a resurfacer for fixing an entire floor. Something that I know will work is to put in a ply subfloor on treated firring strips. Then you can always nail your flooring to that or float over it. Don't forget a vapor barrier test. Take a few square feet of plastic and tape it to the concrete. Leave for 24hrs or so and take it up. If it is damp under the plastic you need a vapor barrier. The mfgr will have that info too as to what you need.

[Cheeky]

if it's not close to being perfectly level, your floor will bounce. it's up to you if that's ok or not. i just spent a week leveling my bathroom floor, taking up the sub, and sistering a couple joist, blocking, planing a couple down, and now it's level as can be (it was really off to start).

you can either use a self-leveling compound, skim it, use furring strips and then lay down that dry-core (looks like osb with a plastic bottom with round risers to keep it off the ground). it's in your best interest to lay down a vapor barrier like david said.

[drumpriest]

As all the above have said, make sure that you lay down a vapour barrier, you should test your slab for moisture. (just duct tape down a 12"x12" piece of plastic for a couple of days, and see if condensation occurs.

One easy trick to take out the larger gaps is to use shingles. If the dip over a span is large enough to slide a shingle under, do so. glue in place, and done.

[Pappy]

Looks like a laminated wood over an MDF core. Most of that type can be floated over concrete.