Concrete – float a tongue-and-grooved 1×12 pine floor over a concrete slab on grade

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I have bare concrete floor that was, until recently, covered with carpet. After recently seeing a friend of mine purchase raw pine, shape the tongue-and-groove himself, and seal it to achieve a wonderful result, I wanted to do the same. The difference is that he was nailing directly to an existing wood floor, and I'm going over a concrete slab on grade.

I'm leaning toward a floating installation because I'm doing it myself, so it's less cost and less effort. Almost everything I've seen is suggesting that the strata should look like so (From bottom to top):

  1. concrete slab
  2. moisture barrier
  3. 3/4" plywood (fastened to concrete)
  4. moisture barrier
  5. hardwood nailed to plywood

However, I'm thinking that I'm going to run into issues with door clearances using this approach. Can I use thinner plywood in layer 2? Or my alternative thinking:

  1. concrete slab
  2. moisture barrier
  3. hardwood glued at t&g joints

Does this approach make sense? What are the potential issues? Does gluing the joints help or hurt?

Best Answer

You can float wood flooring installs over concrete. Moisture is your primary enemy here, and uneven concrete will also be evident in the finished result.

I would consider painting on a moisture barrier, and then using a moisture/sound/mold/mildew/pad atop that.

You should absolutely glue the joints. Set the first three courses straight and true and let the glue dry overnight. Afterwards, glue each joint and use blue painter's tape every few courses to hold them together.

An uneven floor will show up more if your wood isn't beveled, and you'll notice dips with "springiness" in the finished wood floor.

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