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Wood flooring on concrete


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I've got a 3 story condo building, new, w/solid wood flooring installed on the concrete floor. It's all scalloped. I suspect no moisture barrier.

I know solid flooring is not approved for installation below grade on concrete. What about a 3rd story condo?

I'm reasonably sure there is no moisture barrier, because the builder has gone over their installation procedures & there's nothing that even suggests they used a moisture barrier. He's saying the scalloping is a "normal" response to the wood being installed over green concrete.

Of course, this has me flummoxed, and suspecting all manner of stuff.

Anyone got a good reference for installing wood flooring on concrete?

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Some of the newer glues have a moisture barrier built into them just for this appalication. I do alot of inspections on new condos and most have wood over concrete on the upper floor levels. Some of the problems i can imagine is pushing the job to quick and not giving adequate cure time. I even seen one job where the ongrade floor slab had wood installed, they laid sheet vinyl first for a moisture barrier.


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That's one of the issues I'm researching. No one seems to know how the wood is fastened to the concrete.

This is just one of the mysteries of this puppy. You wouldn't believe the list of stupid stuff. Topping the list is the balcony that drains back toward the building. I wish my customer would simply bail.

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Hi Kurt,

Don't know if any of these will help. The top link is the search string, the next three are selected from the results.

http://www.google.com/search?hl=en&q=in ... tnG=Search


http://www.hardwoodinstaller.com/hardwo ... ncrete.htm

http://www.woodfloorsonline.com/techtal ... tions.html

The builder needs to get a clue. Sure, expansion is a normal response to wood installed over concrete, but that doesn't mean that it's okay to install wood over green concrete. They should have waited at least two months before attempting it and even then they should have taped a sheet of plastic to the slab and waited 24 - 36 hours to see if the underside got wet. If so, and they absolutely had to put the floor down at that point because of scheduling, they should have coated the slab with a sealer such as Sila-Crete (http://www.permacrete.ca/products4.html) and used used Warm-Crete (http://www.permacrete.ca/warmcrete.html) or a similar product to absolutely ensure the floor would stay flat regardless of what the concrete did.

Now, when the moisture level in that concrete gradually drops and the floors start to dry out, they'll flatten out a little bit but the homeowner will start to see compression set gaps everywhere and that will upset the owner more than the scalloping. There's absolutely no way to correct compression set. The gaps will be too narrow to hold any wood fillers for very long and those floors are going to be pretty unsightly.



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I have seen hundreds of homes with wood floors glued to concrete. In MS and in other parts of the south it popular to use old heart pine for flooring. With concrete slabs they glue it directly to the slab. One installer out of Brandon, MS developed a method using Bostix brand glue. The key as others have said is that the concrete needs to be dry and not green.

With the scalloped or cupping, the wood is warping and is most likely trashed.

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I am installing two wooden floors right now, one is 3/4" x 5" Brazilian Cherry, nailed onto 3/4" plywood on 4x4"s. The other is a 3x8" "Pergo" type, "floating" floor.

The reason I questioned about expansion in the gluing technique is because I imagine that the concrete expands differenty than the wood and I wondered if that would cause a problem.

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