# Hardwood floor on concrete slab



## westend (Jul 11, 2012)

My potential builder and I got into a great conversation about slab vs traditional foundation with crawlspace and the merits of a slab from an efficiency standpoint. From there we talked radiant heat systems etc, then the trickiness of installing wood floors in this sort of configuration.

Anyone have experience with installing (and living with) a hardwood floor over a slab foundation? Or slab+radiant heat+hardwood?

I won't use laminate or composites... So it will be wood and stone/tile at the entries and around the wood stove.


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## dirtman (Sep 15, 2011)

I have installed several hardwood floors over slabs but always on treated two by fours anchored into the slab and above a vapor barrier. I have always covered the two by fours with 3/4 plywood or OSB. You would not be able to use a radiant floor installed in the concrete though and we never thought that pex stapled directly to the wood was very effective. When we install hardwood in this manner we leave a space every couple of rows the width of a penny because the floor will want to expand. Any moisture coming up from the curing slab will ruin the floor so it is better not to install it over a freshly poured slab. Several months curing time would be best.


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## Darren (May 10, 2002)

You're facing the same problem they have with gym sub floors poured on grade when the flooring is installed later. There's a very heavy plastic material that's designed for those cases. That is laid down before the concrete is placed. There's a special tape that is used to seal the seams. Any cuts also have to be sealed with the tape. 

The contractor later runs a test to determine if moisture is present. Once the test results are OK, the hardwood can be installed. You still have to allow enough time for the moisture in the curing concrete to escape.


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## tallpines (Apr 9, 2003)

Our floor has radiant (pex) heating --- covered with 2 inches of cement --- which is covered with hardwood in the two bedrooms, wide pine boards in the great room/kitchen and tile in the bathroom/utility room.

Underneath this whole flooring set up is a full sized basement.


The joists in the basement ceiling were placed closer together than normal to accommadate the extra weight of the 2 inches of cement that was to come.

Next the floor plywood was put down.

Then we added 2 X 2's on top of where the joist lines were ---- leaving spaces at each end for the Pex tubing to lay.

I (an old Gramma) stapled lots and lots of Pex tubing in place.

I put one line of Pex tubing in between all the joists except in the Great room/ kitchen area where I laid 2 lines inbetween each joist because those areas have 22 foot high vaulted ceilings and LOTS of windows.
I figured it would need more heat than other areas of the house.

To help control the heat in separate area's of the house, I installed the Pex in 5 separate units so at any time we can shut down any one of the areas.

After the Pex was in place, the cement was brought in and poured 2 inches thick, between the 2 X 2's, completely covering the Pex.

(Make a MAP of where your PEX lays before covering it, so if any drilling needs to be done for electric wire or plumbing, you'll know where it's safe to drill without hitting any of the Pex.)

Then the hardwood and wide pine board were installed making use of the 2 X 2's for anchoring it.

We've used this system for 10 years now and it works very well.


In the cold of winter, it's wonderful to have WARM floors.

The hot water the creates the heat is warmed by an outdoor wood burning boiler.

Because radiant heating is slow, the gas fireplace we added helps take the chill off in the early mornings, and on those days of -20 to -40 degrees when we need a little extra warmth.


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## Darren (May 10, 2002)

Did you use light weight concrete?


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## tallpines (Apr 9, 2003)

I'm not too familar with varieties of cement.

I drew up the floor plan for our house, and told out builder what we wanted.

He in turn talked to out local cement provider and it all got done.

I'm guessing it is a lite weight cement but can't be sure.


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## Darren (May 10, 2002)

Light weight cement is used for multiple story buildings. Rather than use the normal aggregate it uses a heat treated shale. It weighs over 20% less than normal concrete.


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## gimpy (Sep 18, 2007)

I'm also working with a basement floor and wondering what to do. I don't want to spend the money involved in adding a floor on top of the concrete. In one corner of the basement the moisture test looked positive (leave a 1 square foot scrap of plywood there for twenty four hours and look uner it and it looks but doesn't feel damp where the wood had been) There's a tree near the foundation there that I guess we'll have to get rid of.

Anyone have tips about acid etching? Is it expensive?
I was thinking leaving the concrete and using some area rugs but not carpet.
Another thought was simply painting the concrete. Any tips?


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## dirtman (Sep 15, 2011)

If you paint it use the two part epoxy paint. it will last much much longer.


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## jwal10 (Jun 5, 2010)

This cottage was an old carriagehouse. It had a concrete floor on grade. I Layed down tar paper over the concrete, shimmed the treated 2"x4"s (layed flat) to level, then added 3/4" plywood on top, glued and screwed down. Recycled oak flooring on top of the plywood. Never have had a problem in 30+ years....James


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