Earth Contact Built Homes
We received a question from a homeowner about installing our floors over a concrete slab in an earth contact built home. Although I am not familiar with this type of home, I am very familiar with installing our floors over slab as dipicted in the photo to the left.
Contrary to belief by many, you do not have to have a floating floor, or an engineered floor, if you are planning on installing wood floors over a concrete slab. What you do have to have is the best quality wood to start with, and the basic knowledge of how to do the installation, for your specific needs. So many of our floors are either glued directly to slabs, or installed over 3/4" subfloors on slab, especially in areas throughout the southeast. (Click here to see a video on the subject.)
Let's start with the wood itself. The best quality planks will come from the slowest growing trees, and from the center of those timbers. The more heartwood and the tighter the growth rings, the more stable the planks will be. A 4" red oak plank with 1/2" between the rings, will move more then a 12" plank with 1/6" between the rings. A plank with 10% heartwood will take on much more moisture then a plank with 70% heartwood. Then air drying these planks for a long period of time before kiln drying them will add tremendous stability.
Then the next decision is whether to glue directly to the slab or to use a 3/4" plywood or OSB sub floor which is then nailed and glued to the sub floor. The deciding factor here is what you have available for height. In other words, can I get away with 3/4" flooring and 3/4" sub floor, for a total of 1 1/2" height, or am I limited to 3/4". If you are limited, then you will want to glue directly to your slab. We can also mill your floor to less then 3/4" if you are really limited.
Checking for moisture in your slab is easily done by taking a sheet of newspaper and taping all of the edges down and then checking it a few hours later. If it is wet, your slab needs to be cured more.
To glue directly down to your slab, use a concrete sealer first. Bostik's MVP works great. Then the next day you can glue directly to the sealer with a full spread mastic.
Installing over a sub floor is always less expensive, and takes less installation experience. Seal your slab by covering it with a 6 ml poly, then cover it with a 15 lb. roofing felt, then nail your sub floor down using a concrete nail gun. Advantec makes a great OSB sub floor that is impregnated with a wax to help seal out moisture. Your floors can now be nailed and glued just like a typical installation.
If anyone has any questions regarding this process, please give me a call for further explanation.
Author's Name: Rick Menard
Posted Date: March 19, 2008 at 9:22 AM
Filed under: DIY - Do It Yourself, Rick Menard
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Tags: Carlisle Wide Plank Floors, concrete, earth homes, engineered, glue direct to slab, hardwood floors, heartwood, sealing concrete, slab, slow growing, stable wood floors, subfloors
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I live in California, four miles from the Pacific Ocean. I currently have an engineered hardwood floor that is floated over concrete. We recently had a slab leak, so our current floor is ruined and has to be replaced. I have been researching new wood floors and have been told to stay away from solid wood as I live so close to the ocean. They say that the wood floor will change/expand over time. I think your floors are beautiful, and see the pictures of the wood floor in the house right on the waterfront. It seems as though your product can be installed on a concrete slab in a house near the ocean.
Also, I would like to install myself...I have read about the process of installing over concrete. I have seen my floating floors installed and it did not seem so overwhelming. Is gluing the floor down much more difficult than floating a floor?
I don't think I have room to install a sub-floor first, but would you recommend a DIY installing over concrete or is it too complicated to risk?
Posted by L. Mroch on April 13, 2008 12:14 AM
Dear L.
Yes, we have plenty of experience with our floors both over slab and on the water. The key is the quality of the wood we start with, the way we dry our timbers, and using proper installation methods. Since you do not have the height allowance to use a sub floor, you will glue directly to the slab.
You sound like a person that is willing to learn, and you can install the floors yourself. I have taught a few DIY homeowners gluedown methods, with great success. I would not call it easy, but with some patience, your floor will come out beautifully.
Please let us know if you need any more information, and I look forward to hearing how your project came out.
Best regards,
Rick
Posted by Rick on May 9, 2008 2:11 PM