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El Buey 07-31-2007 11:21 AM

Hardwood over concrete slab
I'm going to install my hardwood flooring over 3/4" CDX plywood . The plywood will be installed over the concrete slab. My only real option is to nail the plywood using concrete nails. What length of concrete nail should I use, and will these nails really keep the plywood in place "forever"? Also, since I don't have floor joists to determine which direction I have to lay the hardwood, is there a rule of thumb ? Gracias

JazMan 07-31-2007 08:28 PM

I think you should re-think this method. Plywood should not be installed over a slab. It will in time absorb moisture, even when the concrete seems dry. If that happens, it will all buckle. Also, how would you fasten the hardwood? The regular cleats are 2" long driven on an angle.

There might be a way to install 3/4" solid hardwood over a slab? But I don't think this is it.


Krichton 07-31-2007 11:58 PM

You have to apply a vapor barrier of asphalt felt or building paper using mastic on the slab first and then another layer of polyethylene film and then you secure the 3/4" plywood to the slab using power-actuated fasteners. OR you can simply buy engineered hardwood planks and glue them directly onto the slab.

El Buey 08-01-2007 07:12 AM

hardwood over slab
Thanks for your insight! I did not mention that I was going to lay polyehtylene barrier over the slab first. then the CDX (exterior) plywood, then asphalt felt. THEN the hardwood. I have been to various websites ("how to install hardwood flooring over concrete slab") and they all recommend this method as one of two methods. I live in Costa Rica and the "experts" here want to embed 2x2's in the fresh slab, then nail the flooring to the 2x2's. I nixed this idea immediately until I investigated futher. And power actuated fasteners? Dudes, construction guys here cut rebar with a hacksaw, and most still mix their concrete by shovel. Now the JazMan has introduced "2 inch cleats" into the formula! Any more suggestions will be appreiated-or maybe I should go with a basic compact dirt floor! El Buey

Krichton 08-01-2007 09:30 AM

Why don't you just buy indoor outdoor carpeting? You know the fake grass one and call it a day? :)

KUIPORNG 08-01-2007 10:39 AM

If you nail the hardwood onto the 3/4 plywood which stick to the concrete... you basically has approx 1/2 to 3/4 nailing depth for the hardwood... I wonder this is good enough depth for the hardwood to stay solid...

bjherron 08-01-2007 03:08 PM

I laid down asphalt, vapor barrier, 3/4" plywood, and 3/4" brazilian cherry when I lived in Florida. I lived there two years, and it seemed fine. I secured the plywood to the concrete with about 16 tapcon screws in each sheet. It was a pain, but the floor did not squeek at all!


El Buey 08-01-2007 05:08 PM

hardwood over concrete slab
The Jazdude mentioned 2 inch long fasteners- he's probably right. Screws may be the way to go but I have about 700sq. ft. to do, no fun. Maybe Krichton has the best idea with the fake grass. After all ,the NFL season is just around the corner... tomorrow I'm going to talk to a company that says they glue hardwood over slab with a special glue just for this purpose (imported from the USA:thumbup: ). Anybody have any experience with this method????

JazMan 08-01-2007 09:30 PM

Sure, it's done all the time, but not for 3/4" solid hardwood. Solid hardwood has to be nailed every 8" more or less. You can use engineered hardwood which is glued to almost any subfloor. Engineered is made from several hardwood plies. The plies are laminated in alternating directions so that the board is more stable, and because it's any where from 3/8 to 1/2" thick, it has some flex too.

Forget the screw idea, that is not going to work at all. What does the manufacturer of your hardwood say? Oh...thenailer looks something like this;...


El Buey 08-02-2007 07:42 AM

Hardwood over concrete slab
Remember folks, I live in Costa Rica. We stopped wearing loincloths just a few years ago. Now, in order to find the manafacturer of the hardwood that we are going to use( Nispero or Corteza) I think I'd have to search for God. I can saythat the Nispero is 7/8" thick, 5" wide and a mix of lengths from 1' to 4', oven dried tongue and groove . The Corteza 5/8" thick and 3" wide. I want to see this special hardwood glue first and read the manafactures claims. At some point I WILL make a decision. Thanks for the airtool reference Jaz, I'll be surfing over to that site shortly. El Buey ( muy confundido )

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