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AlfredMD 08-08-2012 09:02 AM

How is my hydronic heating and tiling plan?
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I am going to DIY hydronic heating and tile on a slab (family room). I made plan A and plan B. Please comment. I prefer B to A for lower thickness.

Will my floor fail because of something that I overlook? Are there modifications you suggest? I need your help.

Some answers to potential questions:
1. Why Hydronic? Because electronic heating is expensive in material cost and expensive to run. It is a big room (240 SQFT) and the adjacent basement provides an easy access to equipment needed.
2. Why foam board (wedi)? Because I want to insulate the slab. Wedi under tile is rated "light commercial" which means it is strong enough for my purpose.
3. Why noble seal? (why not Ditra?) Because noble seal is cheaper (?) and thiner (?) and I heard that I need a layer between tiles and heated backer boards (SLC here).

Thank you!

Alfred in MD

AlfredMD 08-11-2012 10:52 PM

Well, It seems nobody is interested in this topic.

I did some research myself. It seems one possible issue with my plan is the fact that PEX tubing expands and contracts. I start to worry the expanding tubing might force upward, and if the structure above the tubing is not strong enough the tile might be pushed upward and crack the grout line.

For plan B I might need to add some kind of mesh in the SLC to reinforce it. The tubing manual from a manufacturer call for concrete of 1 and some fraction of an inch above the tubing. I need to think carefully before I put down the tubing.

oh'mike 08-12-2012 06:34 AM

Sorry---I am going to move this to HVAC---your plan is not the best---

Typically the hydronic tubes are covered with a poured on concrete type covering---Not my area of knowledge---

beenthere 08-12-2012 11:16 AM

Most of pex's expansion will be in length, not much in diameter. the more material on top of pex, he higher the water temp needed to heat the area. All material has an insulation value/resistance to heat transfer.

B would work much better for heating. but with wonder board over top of the pex, instead of thinset.

AlfredMD 08-12-2012 11:41 AM

1 Attachment(s)
Hi Beenthere,

Thank you for your comments.

One question is, why do you think wonderboard instead of thin set on top of PEX is better? In plan B thin set was used to install nobleseal, and then thin set on top of that to install tile. SLC was used to fix the PEX in place. If I add a layer of wonder board on top of PEX, it becomes plan A. Would you explain? Thank you.

I also modified plan B to make plan B1, because SLC was expensive, and I plan to embed tubing in wonder board, then pour SLC on top of both the PEX tubing and the wonderboard. Does this make sence?

Alfred in MD

beenthere 08-12-2012 11:50 AM

Thinset could crack from expansion of the pex. Wonder board won't.

AlfredMD 08-12-2012 12:05 PM

Hi Beenthere,

Thank you again. Two more question,
1. Will SLC in plan B1 avoid being cracked with PEX under it?
2. Could NobleSeal in plan B or B1 mediate the crack problem?

If both answers are "no", I may go with plan A. Thank you!

Alfred in MD

beenthere 08-12-2012 12:25 PM

SLC won't stop the thinset from filing in at the ends/loops of the pex.

Noble over top of the Pex and SLC as long as its ran as far back as the thinset will be used, should mitigate the cracking. As the thinset won't be able to encase the loop ends of the pex.

AlfredMD 09-16-2012 07:25 PM

Just an update. I finally used thinset-wediboard-PEX-AL-PEX and reinforcing rebar in 1.5" deckmud-thinset-ditra-thinset-tile. The thread is in flooring,

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