Tile Over Hydronic Radiant Heat

angus242

I am doing a bathroom floor. Here's how is was planned:
subfloor = 3/4" TG
radiant panels = 5/8" ply w/aluminum foil layer across top

I was going to use 1/4" CBU over the foil then Ditra, then tile. However, I'm a little confused about the CBU over the foil. There should be a layer of thinset under the CBU but is it a good idea to put that over the foil-lined ply? I can't find this exact scenario in the TCNA handbook. The aluminum is thicker than regular foil but not quite thick enough to be a plate. Actually, the manufacturer of the radiant board calls for installing this way but no one anywhere states anything about thinset over the radiant for the CBU.

Anyone care to throw some advice around on this one?

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cleveman

haven't heard the colonel reporting in lately. thought you might have fallen in battle. any chance of a wet bed instead of that funky stuff which the pipe circulates through?

angus242

Nope

Yeah, the Colonel has been crazy, busy. Moved (yep actually got financing on a house...AND got it for a steal!), trying new suppliers, new marketing, new logos/signs and some of the craziest customers you can imagine! I have to post in the remodeling section about one of my kitchen remodel customers. AA called and they're looking for a missing member !!!

Stay tuned for that one.
EDIT: If you have some time on your hands, check out the story. It's long but 100% true!
http://www.contractortalk.com/f18/not-so-simple-remodel-46861/#post519160

angus242

Well I talked to (floorboard) tech support and they claim it's OK to use thinset over the aluminum. He said to use modified and to not mix it too thin.

Does this jive with you guys?

Anyone?

Bud Cline

Angus I have never used that product or been around it so I can't be of any help. I can tell that thinset on metal don't get it. I would be afraid of that technique.

How about you contact a techie at one of the thinset manufacturers and see what they say. Probably one of the sharpest techie guys around is a fella named "Anthony" at Custom Building Products. Give him a call in California and see if he can help you. Call their published 800 number.

angus242

Thanks Bud. I will call him tomorrow and see what they have to say about this. I asked the tech support guy at the thermalboard place like 3 times to make sure I understood him correctly. I don't feel good about thinset over the aluminum myself.
I'll post his (or any others') replies.

Bud Cline

It will be interesting to see what you come up with. probably just more contradictions of the industry.

Winchester

I agree, I'd like to hear this as well.

__________________
Ryan

angus242

Well no one has any recommendations. From thinset manufactures, to the thermal board manufacturer to the TCNA. Bottom line is the thermal board company (cough, cough, infloor, cough) has not bellied up to the testing table, therefore no manufactures or organizations can truly recommend a procedure based off real testing. The thermal board installation instructions go against many tile installation methods so I'm abandoning their procedure.

I guess I'm on my own and I'll just have to be a handyman hack and figure it out myself.

Winchester

Well, will the suppliers of the foil-lined ply (the ones who tell you to use thinset on it) warrantee this method?

If the answer is no, then maybe you should consider another product?

__________________
Ryan

SLSTech

I see what you mean - they don't specify using thin set to hold down the backer board, but they point out that you need a Crack Isolation Membrane applied. Can this product work under the sub floor?

Handyman Hack says - follow their directions - screw the board down & go from there - it should work.

GC says - no testing - no install unless Homeowner wants to sign a waiver

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angus242

I talked to Infloor's technical department twice about this. Their only reply was that's it's been done before and they've never heard of a problem. I still say when push comes to shove, they're not going to warranty a tile failure since there's plenty of other areas to blame it on.
I'm just not going to use this product. Sucks as now the project is on hold until a replacement material can be found.
They want radiant heat over the sub floor. This is only a small 4X6 bathroom that they are using as a guinea pig. As they change the flooring throughout the rest of the house (most of which will be hardwood), they are going to add the radiant as they go.

Onto plan B...

So a word to the wise, as a tile installer, be wary of Infloorboard!

orson

Angus,

Is your primary worry that the thinset won't bond well to the foil face?

Even if it did not bond well I'm not seeing where that would cause a failure in the rest of the tile assembly sitting on top of it. Woudn't it just be effectively uncoupled?

I'm not advocating using it, just curious if you are anticipating a specific problem.

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Kitchen & Bath Remodeling PA- Bathroom Remodeling Lancaster PA
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MAD Renovations

Do you have any contacts at Schluter..... They can walk you through exactely what needs to be done. The testing that they have done with thier products to ensure that there are no failures is amazing. If you do not have any contacts there PM me and I can give you a number for some of the guys up here in Canada... I am quite confident they will have your answers and be happy to help.

Cheers

angus242

Every manufacturer I know of that produces backerboard requires the use of thinset under it, so that ruled out not using any. Furthermore, I'm worried about the fact that the thermal panels are constructed of MDF. Here's one of the uninstalled panels. You can clearly see the torn aluminum as well as the lack of it in the bottom of each channel. The moisture from thinset can easily penetrate into the MDF through various means. I've actually contacted the TCNA about this installation and they agree with the bad idea of thinset over the MDF or no thinset at all concepts.

I've started researching alternative products at this point.

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angus242

Thanks but my concern was not with what happened above the CBU. I have been using Ditra for a few years now and have had a great experience with it. However, thinset over MDF or no thinset under CBU I'm not cool with

orson

Aha!! Now I get it, I was thinking you were talking about something more like Warmboard.

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Lancaster Remodeling Contractor - Lancaster Remodeling
Kitchen & Bath Remodeling PA- Bathroom Remodeling Lancaster PA
Custom Kitchen Remodeling PA - Ruby Construction FaceBook-Lancaster Bathroom Remodeling

Winchester

Would bekotec work?

__________________
Ryan

angus242

No. I mean, yes. Well in this case it would work. However, this is only step #1 in what will eventually be a whole-house project. Since a majority of the house will be covered with hardwood, a cement bed is not an option here. The guy who spec'd out these panels was taking into consideration the floor height overall. Either way, I wasn't getting paid to design anything. Now, for the sake of keeping this project, I'm suggesting what will be used. I'm looking into a layer of 3/4" ply, router out our own channels, drop in aluminum plates (see below) and be done. The bathrooms would get 1/4" CBU, Ditra and tile whereas the hardwood could go directly onto the ply. That gives almost equal height throughout.

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sponge racing

Angus what was your outcome with this project? My only difference is the plumber used osb instead of plywood between the pex. Kinda not sure on putting the thinset under the hardie board since its osb!! Same plates were used also.