# hardwood over concrete methods.



## Rich D. (Oct 14, 2011)

Hey guys. 

I'm soon to lay about 500 sq ft of 3/4 harwood flooring over an old concrete slab. Previously there was carpet there so height issues with doors should not be a problem.

There is carpet in some rooms remaining so id like the hardwood to meet the same height as the carpet (1 1/2"about) so I dont think a glue down or a floating floor would work anyhow.

I know hardwood isant recommended for this type of install but this is what they want. 

I've layed hardwood over a subfloor a bunch of times but never concrete.
These are the different types of methods I'm thinking about. Please critique my methods and tell me what you would do in this situation.

Method 1- sleeper system 

6 mill vapor barrier. Overlap and tape seams and also run up wall behind base. Then install 1x3's 12" OC and shoot or screw down. Then install 3/4 foam board insulation between the sleepers. Then install harwood.

Method 2- floating subfloor

Install 6 mill vapor barrier. Overlap and tape seams and also run up wall behind base. Then lay down 2 layers of 3/8 or 1/2 exterior ply in opposite directions leaving room for expansion and contraction and fasten together someway. Then install rosin paper and lay the flooring on top of that.

Or... Method 3- ply directly on the slab.

Again I would Install 6 mill vapor barrier. Overlap and tape seams and also run up wall behind base. Then shoot or screw down 3/4 cdx to slab. Install a rosin paper and install flooring to that.

Please let me know the best option I have and what you would do. Thanks in advance...


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## Rich D. (Oct 14, 2011)

BTW I forgot to say this isant a basement its on ground level.


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## astor (Dec 19, 2008)

Any of them will be OK. You can corporate #2 and #3, cut the 3/4" ply 16" into wide strips and float. Check this tread for ernesto's system, maybe he can chime in. I did not tried, but it is in my list for first coming job.
I would use Aquabar or similar for underlayment, rather than rosin paper. 1 1/2" cleats.
Calculate the cost,I believe #1 is the most costly.

PS. Found the tread and made corrections.


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## Floormasta78 (Apr 6, 2011)

3/4 solid directly over concrete , you looking at doing shorts. I would do sleeper . 2x4 face down , bolt to the concrete 3/4 plywood and nail down..


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## Rich D. (Oct 14, 2011)

Floormasta78 said:


> 3/4 solid directly over concrete , you looking at doing shorts. I would do sleeper . 2x4 face down , bolt to the concrete 3/4 plywood and nail down..


I don't think I have that much room. 11/2" max finished floor height.


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## PrecisionFloors (Jan 24, 2006)

Personally I like the floating method. It is more labor intensive but has its perks over the other ones imo. No penetrations in the moisture barrier is the big one. Plenty of room for movement. No fastener issues, no drilling. Should be quieter than a sleeper system for sure. The one big downside is the slab better be dead flat or made to be so a keen eye and feel for prep is needed. Another method would be to fullspread urethane adhesive/moisture barrier the plywood down. More costly but that would be the ultimate method imho.


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## PrecisionFloors (Jan 24, 2006)

Rich D. said:


> I don't think I have that much room. 11/2" max finished floor height.


Yeah that's the worst one for elevation issues for sure - you're looking at 3" of finished floor height


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## Rich D. (Oct 14, 2011)

Has anyone ever troweled on something like the bostik mvp or something along the lines of that then the 6 mil? Would that help to seal nail holes? Or something like redguard? Anyone ever use ice and water shield? Just wondering?


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## Rich D. (Oct 14, 2011)

Or how about the bostik seal n' grip to actully glue down cdx? The hardwood over that? Sorry just brain storming!


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## PrecisionFloors (Jan 24, 2006)

Rich D. said:


> Or how about the bostik seal n' grip to actully glue down cdx? The hardwood over that? Sorry just brain storming!





PrecisionFloors said:


> Personally I like the floating method. It is more labor intensive but has its perks over the other ones imo. No penetrations in the moisture barrier is the big one. Plenty of room for movement. No fastener issues, no drilling. Should be quieter than a sleeper system for sure. The one big downside is the slab better be dead flat or made to be so a keen eye and feel for prep is needed. *Another method would be to fullspread urethane adhesive/moisture barrier the plywood down. More costly but that would be the ultimate method imho.*


:whistling


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## Rich D. (Oct 14, 2011)

Yes thank you precisionfloors as soon as I read your post I looked up the name of the product and forgot to quote you in! Thank you for that suggestion!


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## Rich D. (Oct 14, 2011)

Ok guys this is what I decided to do.

The floating subfloor method.

- 6 mil vapor barrier 
-2 layers of 11/32 exterior ply layed in opposite directions. Stapled and glued toget
her.
- rosin 
- then lay flooring with 1 1/2" staples.

Sounds good? Sugestions appreciated.. thanks :thumbsup:


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## ernesto (Apr 11, 2011)

Rich D. said:


> Ok guys this is what I decided to do.
> 
> The floating subfloor method.
> 
> ...


Perfect. But for a basement or below grade step it up a bit and use Bostik MVP4 then the 6 mil.


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## Rich D. (Oct 14, 2011)

Thanks Ernesto! :clap:

thanks for everyone's input


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## Rich D. (Oct 14, 2011)

One last question. I'm doing the floating subfloor method over concrete with 2 layers of 3/8 ply to make a total of 3/4 inches in thickness.. the client picked 5/8 bamboo. Is a 1 1/2 flooring staple going to be too long now? Or will I just make it?


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## ernesto (Apr 11, 2011)

Keep this handy in a file Rich.

http://www.powernail.com/home/depthchart.htm


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## Rich D. (Oct 14, 2011)

Thanks ernesto! 

Thats a great link! Answerd my question and then some! 

It's in my favorites!:thumbup::clap:


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## ernesto (Apr 11, 2011)

IMHO the keyword when installing hardwood (especially solid hardwood) on a subfloor over concrete is "isolate"!

There is no reason you should need to fasten, gluedown the plywood to the substrate, it only allows more issues to arise like fasteners popping, adhesive failure, moisture issues etc etc. 

Seal it with something like MVP4, cover with six mil....cheap extra protection and then lay the plywood. Of course it should be flat. If leveling is needed use exterior grade patch or SLC.


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