# ?? About installing hardwood over concrete above grade??



## maleko (Jun 6, 2007)

A customer wants to install a pre finished 3/4 hard wood floor over concrete.
its from bella wood. Their catalog says it can be done but you must use a adhesive mat ?? I have never heard or seen this. It almost looks like that water and ice shield you see on roofs.
Is there any tricks or options i have?

I have installed many pre finished floors but they have been on wood sub floors . This will be my first over concrete.

i am a finish carpenter by trade, and i know i can do it.

just looking for some thoughts and options..

Thanks in advance


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## jamestrd (Oct 26, 2008)

I dont know what you mean by "adhesive mat" and have no idea what they refer to..
i wouldnt trust LL as a legitimate source for anything.

however, they may be talking of Seka system..

it is a slotted foam underlay in which you strip glue in the slots and lay the wood into this..

picture a grill...its sort of like that..

I personally dont care for it..

Bostik and Seka are not guaranteeing their adhesive for solids over Concrete..
im kinda old fashioned with some things.


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## rusty baker (Jun 14, 2008)

Solids on concrete have a bad history of failure. LL products do not have a good reputation.


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## nymasterfloors (Jan 28, 2011)

I definitely would not recommend hardwood on concrete though I have done it if HO is persistent on it make them sign a waiver also I have done it glue down with vapor barrier underneath as customer requested.


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## WNYcarpenter (Mar 2, 2007)

nymasterfloors said:


> I definitely would not recommend hardwood on concrete though I have done it if HO is persistent on it make them sign a waiver also I have done it glue down with vapor barrier underneath as customer requested.


How do you glue down with a vapor barrier?


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## CadetC (Aug 21, 2009)

Is finished floor height critical? How about to pin 1/2 inch plywood to concrete and then install hardwood


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## pinwheel (Dec 7, 2009)

WNYcarpenter said:


> How do you glue down with a vapor barrier?



MVP. Elasomeric coating over the concrete then bostiks best. I've installed a few solid wood floors over concrete with no problems. Put it in my own home last summer, above grade slab, random width, 5,7,9 & 11" No issues to this point. Floor laying flat, with no hollow areas.


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## Repairman615 (Jan 10, 2011)

I have done this using bruce hardwood glued directly to the concrete per the direction of the GC. I suggested 3/4 ply ramset to the slab but he did not think that would be needed (refused).

The adhesive was a trowel type, pretty messy and about $100 / bucket (3gal maybe??). Came in a metal grey can and a lid that was also metal with small metal tabs around the rim bent over to seal it on. Can't remember the brand.

I used straps made by pergo...like a ratchet cargo strap with flat end plate type hooks to pull it togather. I had plenty of gaps from bows that nails would have pulled tight. The clamps made that part better but still I was not happy. I also used weights to help set the wood.

To sum it up, in my opinion it can be done without furing strips or ply as a low to mid quality.
For quality and above, use a substrate like Marine Ply with 30#. :thumbsup:


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## 3bar (Jan 14, 2011)

CadetC said:


> Is finished floor height critical? How about to pin 1/2 inch plywood to concrete and then install hardwood


that does nothing. fastening the floor to the concrete is not the problem. the problem is to prevent moisture from the ground/slab...to get to the flooring.

i havent used that adhesive mat you mentioned, but i'm guessing you glue the mat down first and then glue the floor to the mat?? that sounds like the best way to do it. the mat will prevent moisture from getting to the floor boards.

next best is to put complete coverage of adhesive. like bostik urethane floor adhesive. bostik also makes a vapor-lock wood flooring adhesive. the glue when dry acts like a vapor barrier.

also keep in mind, engineered floors(plywood core with real wood finish layer) are more stable when exposed to humidity/moisture. may want to go that route if you think the floor has excess moisture.


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## opiethetileman (Apr 7, 2005)

i have glued down 3/4 solid to slabs. I have donea complete house with brazillian cherry and its about 3 blocks from the ocean .NO PROBLEMS that floor was put down in 07. I used bostiks best and filled all my bird baths for hollow spots with thinset. In florida alot of floors are over concrete . We have have height issues here with exterior door opening in. I try and suggest a eng hardwood floor for height. I installed a floor in 05 that was solid bamboo and its on the ocean. no problems with that one either. Glues down with bostiks best.


Bostiks is by far the best glue out. i had to do repair years ago from a skylight leak. the glue was strong enough to pull up the concrete with the wood floor.


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## nymasterfloors (Jan 28, 2011)

WNY I used adhesive as per gc instructions to put down vapor barrier then glued on to barrier. IMO glue down to concrete is best way


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## WNYcarpenter (Mar 2, 2007)

Is That adhesive moisture barrier the same stuff you brush on cement backer board?

I just did my first glue down plank flooring on concrete two weeks ago. New floor we poured...6mil, rigid foam, radiant heat (not up and running yet)...the works.

FWIW....I'll share our first time struggles......

We started in the center of the floor like you would if you were splining for layout. We were being careful, but after about 3' everything was shifting even with the lightest traffic. We were struggling....

finally I got a few pipe clamps out, a couple 2x4s and pulled it all together, and added weight here and there. We let it set up for a couple hours. After that it was pretty smooth sailing.

When we ran into bedrooms we braced the first course against the wall.... We had a pretty good system. One guy troweled, the other installed 2 courses at a time, then went back with a rag soaked in adhesive cleaner. Wiped down the planks making sure there were no gaps.

We went through a lot more glue than anticipated...


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## nymasterfloors (Jan 28, 2011)

you def end up using alot of glue even if you trowel it thin gets VERY costly


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## lawndart (Dec 3, 2006)

My company does installations for the Lumber Liquidators here in NYC. The "adhesive mat" the original poster mentioned is a new product called Elastilon. It is sold directly through the local stores, and costs about $2 a sq. ft.

I've done a few installations on above grade concrete without any problems using it. Just make sure you follow these steps before installation. 

1. Perform a Calcium Chloride moisture test of the concrete allowing no mre than 3lbs per 1,000 sq. ft.
2. Make sure the substrate is level within 1/8" over an 8' span
3. Use 6 mil poly moisture barrier installed underneath the Elastilon.
4. The home should be heated 2-3 days prior to installation at a temperature between 60-85 degrees, with a relative humidity between 40-65%
5. Allow the solid wood flooring product to acclimate for atleast 7 days in the area of installation.
6. Watch the videos below. Installation can be tricky without any prior knowledge.

Check out the Elastilon website below for instructions

ELASTILON WEBSITE

Elastilon instruction videos:

INSTRUCTION VIDEO

DEMONSTRATION VIDEO

Overall, I think it is a great product, and very easy to install once you get the hang of it. Good Luck!


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## lawndart (Dec 3, 2006)

nymasterfloors said:


> WNY I used adhesive as per gc instructions to put down vapor barrier then glued on to barrier. IMO glue down to concrete is best way


Around here, we call it a "double stick application". It's very common in New York City, with all the regulations these managment companies enforce.


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## lawndart (Dec 3, 2006)

WNYcarpenter said:


> Is That adhesive moisture barrier the same stuff you brush on cement backer board?
> 
> I just did my first glue down plank flooring on concrete two weeks ago. *New floor we poured*...6mil, rigid foam, *radiant heat (not up and running yet)*...the works.
> 
> ...


A couple of things you mentioned above should be of concern to you. I hope the newly poured concrete was atleast 3 months old, and you should have run the radiant heat system on low setting for 3 days prior to installation.

I hope you did a calcium chloride test on the concrete before (especially over radiant heat), and allowed the product to acclimate for atleast 7 days before in a sealed house (windows, doors installed) with a steady temperature between 60-85 degrees.

Was this product solid 3/4 material you installed?
Was it an exotic species? Exotic species tend to dry out, and check/crack on the ends/butt joints when installed over a radiant heating system.

Make sure you tell the customer, when initially turning the radiant heating system on at the begining of every season to set it to low slowly bringing the temperature up over a period, of a few days, so that they will not shock the floor, causing checking, and extreme contraction/gapping.


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## WNYcarpenter (Mar 2, 2007)

lawndart said:


> A couple of things you mentioned above should be of concern to you. I hope the newly poured concrete was atleast 3 months old, and you should have run the radiant heat system on low setting for 3 days prior to installation.
> 
> I hope you did a calcium chloride test on the concrete before (especially over radiant heat), and allowed the product to acclimate for atleast 7 days before in a sealed house (windows, doors installed) with a steady temperature between 60-85 degrees.
> 
> ...


The poured floor has been in place for 3 months steady room temp at or atleast 60*....1/2x5 engineered flooring......home is sealed. Radiant heat has not been running, and no tests have been taken.....

I completely understand the concerns, and I wish the situation had been different. It's tough to put an entire project on hold to meet optimal conditions. If I were working for myself I wouldn't warranty the work and have the GC sign off.....fortunately, my company can absorb the costs to some extent (otherwise we wouldn't be operating the way we are), granted it's not the best course of action, but we're pretty conscientious.........

That's good information to know in case there is a problem (we're firing up the boiler this week). We didn't even know what product we were using until it arrived in the field.....we had to run to the store to buy glue......SNAFU....

Thanks for your input!


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