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I would like to install engineered hardwood flooring over a concrete slab which is on grade. It is the first floor of the house, there is no basement and the house was built in the 1990's. I have seen vapor barrier sheets, DRIcore vapor barrie/plywood tiles, as well as other methods used underneath the engineered hardwood. Would it make sense to seal the concrete slab and then place DRIcore as well as a foam underlayment down below the flooring? Or would DRIcore or a vapor barrier with an underlayment be enough? Would it be recommended to lay the floor floating or glued down? Or if using the DRIcore, could the flooring be stapled down? I would appreciate all advice! Thank you!

I am in NYC, not in a flood zone and the backyard and front driveway are all properly graded away from the house. There doesn't seem to be any evidence of flooding or water damage. The floor is currently tiled. But I think that was an aethetic thing, as the former owner tiled every room of the house including the second floor.

  • Where are you at? What current flooring do you have? Is the grade slab above all of the surrounding yard? – DMoore Feb 28 '15 at 0:12
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    Talk with the company selling the planks. They are likely to have sound advice based on experience with local conditions. National manufacturers have technical support staff as well. – ben rudgers Feb 28 '15 at 14:03
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I have had 3/4" hardwood floors placed on Dricore on 2 different jobs. One below grade with a foundation drain system the company I worked for installed. Top of the line, no holds barred water control system. The floor went down a is still performing beautifully. 1 1/2" staples were used so they did not go through the plywood so far to poke holes in the dimple mat. This was tested on a piece to insure this would not happen before the flooring was laid. The other floor was done with wide plank flooring, 5 years ago still working great to this day too. So you would not be going wrong if you went with Dricore. I placed this on the concrete without a vapor barrier in either case, but the floor was sealed.

You may need to check what the staples will do with your thinner engineered flooring. Also, you MAY be able to direct glue the flooring to the concrete slab since it is above grade. Since it is a newer home there should be a below slab vapor barrier. Two good conditions to have, so you don't get moisture rising through the slab.

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You don't need to seal the concrete, just be sure it has cured for the correct amount of time.

If you are floating the engineered hardwood you will need at least a basic underlay that offers moisture barrier and cushioning. This protects the floor in case the concrete sweats over time. You can also go with an underlay that offers some temperature insulation as some people find floors installed directly over concrete to be a little cold.

If you glue down you will just need to use an adhesive that has a vapor barrier built into the formula. Floating is the easiest method but gluing down will provide better sound and a more solid feeling underfoot.

If you want to staple you will need to lay a full 3/4" plywood sub floor on top of the concrete. Most warranties will only be valid if it is installed over the proper sub floor and DRICore will not be strong enough to hold the staples.

For more information you can take a look at the BuildDirect blog at the link below: https://www.builddirect.com/blog/how-do-i-install-engineered-hardwood-floors/

  • Hello, and welcome to Stack Exchange. Usually we're pretty sensitive to what might be "spam", but this does NOT qualify. My complements (seriously) on a well-crafted, well-disclosed post, and thanks for the contribution. – Daniel Griscom Mar 16 '17 at 12:22
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If your concrete slab already has poly sheeting under it (it probably does if it was poured in the 90s), you don't need to worry about adding a dedicated vapor barrier. So regardless, don't worry about "sealing" the concrete. Anyway, most closed-cell foam engineered flooring underlayments already constitute a vapor barrier, and that's probably okay even if there's poly under the slab. The problem with having a double vapor barrier situation is that if the thing between them ever gets wet, it doesn't have an easy drying path. But concrete is not moisture-sensitive, so there's no humongous problem with it having a lot of moisture in it and drying slowly the way we would freak out about encasing a sheet of OSB between two vapor barriers and letting it get wet.

So the foam-underlayment-with-a-floating-floor-engineered-hardwood system would be the most economical choice here. If you wanted to have a really bulletproof system, DRICore with real 3/4" hardwood over it is very nice. But it'll raise the floor 1 1/2 inches.

  • Thank you both for you answers- very helpful and informative! I was originally thinking of laying the floor floating. But I have been told that this method can lead to creaky floors and a hollow sound when you walk on them. Would your recommendations be to nail down the flooring using correct length staples that do not penetrate the dimple layer of the DRIcore with a foam underlayment? Or if ceiling height allows to put a real layer of plywood over the DRIcore then foam underlayment and then staple down the floor? Thanks! – Kate Mar 1 '15 at 14:26

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