3/4 x 2-1/4 Oak over Gypcrete

Rudy

Has anyone here used two layers of 1/2" CDX on top of 1" of Gypcrete as a nailer for hardwood floor?

Also, what method do wood floor manufacturers recommend for hardwood over Gycrete?

Unknown

wood over gypcrete

I know people who have used the multiple layers of plywood over gyp, i prefer the method below (in a lot of manufactures install books). Make sure what ever method used is the R-value plugged into the design program for heat transfer. 2 layers of plywood plus 3/4 hardwood has a R2.4.... ugly!

MAKE SURE to do a moisture test BEFORE you cover the floor with anything.

wheels

hr

Not my favorite install

I agree with the method Wheels shows. The biggest reason is it allows the flooring installer to always see the tube!

Here's the deal with sleepers. It's real, real hard to find stable wood these days. Especially 2X2 material as it is cut from thin young trees. Usually lots of knots also. You REALLY want to glue and screw it down as it twists, cups, bows, etc. everything but stay straight.

Next you pour a very wet product against it. Gyp has a lot of water in the mix. The dry 2X2s absorb this and swell. The gyp tends to shrink down from the top when it dries. Leaving a small non heat transfer gap.

When the radiant is fired the 2X2s start to lose that moisture and shrink. Their nail holding ability gets compromised somewhat, and squeaking hardwood is a real possibilty.



If I were to do a sleeper/ gyp application I would look into the laminated 2X4 or 2X2s on the market. They come lazer straight up to 40 feet long, they are the mother of all nail holding products. Very dimensionally stable, they all match perfectly. And they stay this way. Check them out.

Next best would be finger jointed stud material. Basically built up of all short pieces, these studs also stay much straighter.

In a perfect radiant hardwood application, by far the laminets and engineered hardwoods are the best match. The factory applied finishes are incredible.

You could float across the Pacfic on this hardwood and still install it as flooring. It's that good!

If I can't talk you out of strip flooring check out www.launstein.com they have a 3/8" thickness that offers a lot of radiant friendly features, and they have done tons of hardwood/ radiant testing. Catch one of their seminars if you can. They really know their woods.

hot rod

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Rudy

Thanks

Thanks Steve and Hot Rod

I have tried to steer this homeowner towards a laminate wood floor, but they want 3/4 oak.

I don't look forward to laying down tube around all those sleepers but it does seem like a better method than the plywood because of the R-value of the ply.

What spacing is recommended for the 2x2's? 12" OC seems like overkill.

I plan to check out the launstein.com product.

S Davis

Wood over Gyp

I have had very good luck with two sheets of 1/2" Ply, it seems to me to be the best way to go as it lets the wood floor assembly float and it can expand and contract at its own rate. JMHO
The worst installation is wide plank flooring over radiant I have several jobs installed with two sheets of Ply that have 10" plank flooring one is 10,000 sq. ft. and no problems, you do have to watch your moisture content, bring the wood in and let the system run for a while and dry it out.
I have had flooring installers complain about not having wood to nail to with sleepers because of having to cut the ends to run your tubing.
The other problem is you want to run your hotest water to the outside wall and run into the room from there so you put the most heat where your heatloss is the greatest, most of the time the sleepes run the wrong way.
One thing you might want to look at is a wood flooring product called Kahrs(www.kahrs.com) it is a real wood laminated to a man made product wich makes it very stable over radiant,it can be refinished up to three times, has a R-value of about 1.55 and is about 3/4" thick, can be a bit pricey though.


S Davis


Apex Radiant Heating

Rudy

Thanks

Thanks for the response, S. Davis. The Kahrs flooring looks really good. Their picture showing the wear layer of their laminated product compared to solid 3/4" strip flooring makes a good case for choosing their product.

Paul Cooke