Gypcrete with sleepers

radmix

Is it a good idea to install gypcrete between sleepers. The carpenters need a nailer for the flooring so they want to install the sleepers. Its my understanding, with something I read a long time ago that the gypcrete settles and you wont have direct contact between the flooring and the gypsum. You will have a 1/4" gap after the gypsum hardens. Does anyone have experience with this.

Bob Bona_4

Yep, good memory. Also consider the fact that gyp will harbor moisture like a sponge and that can wreak havoc. My last choice for radiant substrate...

Zman

It sound like you are stuck with gyp? I have to agree with Bob.
If you have no other choice, do as the carpenters have suggested. After the gyp has cured, seal it . When they install the flooring they can use a trowel down adhesive that will help with heat transfer and prevent squeaks.
Aluminum plates on the bottom of the joists eliminate this problem and other issues associated with high thermal mass systems.

radmix

I bid the project for extruded aluminum plates but was over ruled by the carpenters who will be doing the install to save $. What other problems do you see with a gyp installation.

Bob Bona_4

Well, other drawbacks are threshold heights, slower response time and potential for overheating the space. "Striping" at the sleeper ribs may or may not rear it's ugly head..

Rich_49

Wow . Carpenters are now specifying radiant installation type ? Can you explain how that works , does the carpenter get paid extra to nail 2x lumber down ? Gyp costs money also , is terrible as a system unless no other option . Amazing how all the trades think the other guy is making too much money .

RobG

And if for some reason it gets wet it will fall apart.

Rob

Paul Pollets

I've installed over 500 systems using a gypsum overpour. Never had a problem with any of these systems. We always specified the correct flooring methods with pre-engineered hardwoods or tile as the finish floor. A few wanted custom hardwood, instead of a pre-engineered product. Those overpours were covered using 2 layers of plywood (Bollinger method).
Gypsum sound proofs and fireproofs the floors and makes the home extremely quiet. The water temperature requirement to heat the home is extremely low with a 80-110 degrees average in Seattle. Almost as low as a radiant concrete slab.
Pouring between sleepers is a bad idea. I'm not sure why the embedded method is overly criticized. It's an excellent medium for radiant. It does have a cost and design factor, to be sure. If it's installed correctly, it works correctly.

radmix

How is the Bollinger method applied. How can you cover and fasten plywood to gypcrete after its poured.

Paul Pollets

The Bollinger method consists of a sheet of visqueen over the gyp, then 2 sheets of min 5/8" ply. The first sheet floats with 1/2" gap at all exterior edges. The second sheet rotates 90 degrees and is glued and screwed to the first sheet. The hardwood in than nailed to the top of the second sheet. Heat calcs must take into account the R value of the plywood and the finished hardwood floors. If not, the room(s) may not heat correctly, or the heating curve would need to be raised where it can damage the flooring.

http://www.theoakfloors.com/don_bollinger.html

radmix

So the hardwood floor essentially becomes a floating floor because nothing is fastened directly to a structure

Paul Pollets

Yes, it's a "floating floor" system

Mark Eatherton

Tuna Quarter. That's Brooklynese for 2 and 1/4. That's the R value of the Bollinger system, not including the thick woven Indian rugs the lady of the house intends to throw down as soon as she can... :-) But it is (almost) idiot proof.

RobG

It would be less expensive to do radiant ceilings.

Rob

Zman

It sure looks like the bolinger system works well.
My point is "why would you".
If your project has minimal solar gain and the finishes are mostly tile and carpet, gypcrete works really well.
If you look at the material and labor costs of either sleeper and glue or bolinger, why would you?
Under floor with plates or radiant ceilings would be more cost effective and would perform the same or better.

I have yet to step on a properly controlled wood floor and had the "warm floor" feeling you get with tile.

I thinks many mechanical contractors just don't like the kind of labor involved so they go the easy, gyp route.

Carl

RobG

Mechanical contractors? Apparently the carpenters are the specifiers on this project.

Rob

Harvey Ramer

A radiant installation is essentially a site built heat exchanger. It isn't even conceivable that someone without radiant or thermal dynamics training should attempt something like this. Yet it happens all the time. Many of the results are a lot more expensive in the long run and a lot less desirable comfort levels.

I have some customers that have told me:
I tell you what I want.
You tell me what it costs.
Then we'll do it.

Those people get the best value. I wish more people took that approach.

Harvey

Bob Bona_4

The concept most laymen grasp. It's the execution that makes success. The devil IS in the details.

Rich_49

Sure hope the engineer was in on the plan . Have personally seen jobs where this type of deal was thought about later in the process . At right around 14 pounds per sq ft in a couple of them it was disastrous . Ever see 2 x 10 lumber at 16" oc and a 16' span with alot of weight that was not supposed to be there ? Not pretty .
There are other things that can be done without breaking the bank nor the structural support beneath .