Advice on tiling onto "overlay" underfloor heating

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Discuss Advice on tiling onto "overlay" underfloor heating in the Canada Tile Advice area at TilersForums.com.

J

Jonner

Hi, my name is Jon

I have already had a look around the forum and it has already been really useful regarding tiling onto an overlay underfloor heating system, but it has raised a few questions!

I will shortly be starting a floor tilling job onto an overlay (water based) underfloor heating system. The underfloor system is in conjunction with an Air Source Heat Pump (flow temperatures about 35deg C).

The PE-RT (polyethylene pipes are laid into a foil insulated polystyrene foam). From what I have read on the forum I am then planning to do the following:

  • Bond on a “backer board” using a flexible adhesive – I was planning on using 12mm thick minimum. Is thicker board better? Should the backer board be screwed down?)
  • Lay down a de-coupling membrane
  • Bond either stone or ceramic tiles to the backer board

Please could you advise if the steps I am proposing are correct and any materials you would recommend.

Any help/advice really appreciated, thank you.

Best Wishes

Jon
 
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J

Jonner

Hi ACT
Firstly many thanks for getting back to me. Thank you for highlighting this potential problem with the adhesive and the aluminium.
I am open to suggestions on what materials to use for this job so if you have any recommendations for adhesive that would be greatly appreciated.
Or could the aluminium foil simply be removed before bonding the backer board?
best wishes Jon
 
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J

Jonner

Hi Andy
Many thanks for your comments, really greatly appreciated.
When you mention priming the foam backed aluminium would something like Mapei Eco Prim Grip be the right thing?
You then mention a flexible leveling compound, would something like BAL - level max be the right things?
Would you propose the self leveling compound instead of the backer board? Or would the backer board be laid and bonded onto the self leveling compound?
Sorry for the additional questions.
Best Wishes
Jon
 
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O

Old Mod

Ok so this type of retro fit ufh installation is the most difficult to deal with from a tilers point of view.
Aluminium spreader plates and tile adhesive are not a match made in heaven, in fact there is a chemical reaction that takes place.
A couple of things first, what substrate are you laying your polystyrene boards to?
Is it a floating floor? (Chipboard laid on insulation with no fixings)
I cannot see in the literature a list of suitable finished floor coverings.
What I can see, is only images showing the finished floor as timber planks on top.
Is this suitable for tiling, have you inquired?
I can not find any fitting instructions either, only a one day acquaint class.
If you have any links to any of the questions it'd be really helpful.
Thanks.
 
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J

Jonner

Hi 3 Fall
Firstly thank you for your time & help with this
The floor is a solid concrete floor, which has been "tanked" with a plastic liner (sheet) CDM membrane (manufactured by Oldroyd). This CDM liner is lapped up onto the walls by about 6inch. The polystyrene boards will be laid onto this.
I have mailed Hetta to understand what floor coverings can be used but from very initial dialogue with them understand "any flooring" can be used! If i get any answers from them i will let you know.
Only other piece of info is that this is being used with an Air source heat pump so flow temperatures will be about 35 deg C
Best Wishes
Jon
 
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O

Old Mod

Ok Jon, kool.
I would insist on a method statement from them in writing.
This is critical I'm afraid.
There's been a lot of social media chatter in the race forums about this and similar products.
Myself and a colleague of mine, investigated a massive failure earlier this year, which happened to be on this type of UFH.
Here is the thread I wrote, my colleague published elsewhere.

https://www.tilersforums.com/threads/retro-fit-ufh-hydrogen-gas-causes-floor-failure.83724/

You will see the importance of obtaining a method statement very quickly.
There have been developments by the company features in the thread, to eliviate this problem, but we'll wait and see what 'hettasystems' have to say first.
Good luck.
 
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J

Jonner

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O

Old Mod

So this is the course of action @Jonner
took over the last few days. I think this may be of interest to you all. I can’t seem to add the pdf attachment he sent but here’s a screen shot.
@LEE MAC, @hmtiling @impish, @Andystiletiling
@Localtiler, @Chalker, @timeless john,
@John Benton.

Jonner said:
Thanks for the advise re getting a method statement from hetta i will contact them and let you know what comes back.
Click to expand...


Jonner:
this is what i have received from Hetta.
Effectively they recommend using ply wood to mount all flooring solutions.

I have gone back to Hetta re concerns re expansion and contraction of ply, and whether backer board would be better. If backer board is deemed better i have asked them to specify and adhesive for mounting it to the aluminium foam backed panels and whether i should prime/seal the aluminum first.

2CCB4465-345D-4AA3-B1C4-C5BC48F68B27.png


Take note of their suggested make up, paying particular attention to the PLY.
 
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O

Old Mod

Here’s the rest of the conversation.
I believe it’s important for members to be aware that there is such stupidity out there and you should be very cautious when it comes to blindly following method statements by companies who clearly have no idea what they are talking about!!

So this is the second response that was received by Jon after voicing his concerns.

Sorry for the delay. Below i have copied in my e-mail and the answers (in red text) that were provided by Hetta.

I see in the diagram (from the instruction manual) that ply wood is specified, as the material to which the floor tiles are bonded.
  • Can you guarantee that ply wood will not expand and contract (move) due to the temperature changes due to the proximity of the underfloor heating?
  • ANSWER:This is an industry standard recommendation and can also use Tile backer boards
Do the ply wood sheets need to be "fixed" to the foil backed foam pipe holder?
  • If so should the ply wood be bonded or screwed?
  • If bonded what adhesive would you recommend?
  • ANSWER: No its used as a floating floor construction
 
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O

Old Mod

Due to my concern raised over the possible movement of the ply wood due to temperature do you think it would be better to use backer board to mount the floor tiles to? See above
  • If backer board was to be used please could you recommend thickness of sheet ANSWER: with regards the thichness we recommend between 6 and 10mm and this is because any more than 10mm heat transfer effected
  • Please also recommend an adhesive with which to attach it to the foil backed foam? ANSWER: There are so many adhesives on the market we do not recommend a specific brand but do insist on a non solvent based adhesive
  • Are there any "primer or sealing products" that you would recommend for use on the aluminium backed foam to ensure that any adhesive could be used? ANSWER insist on a non solvent based adhesive

  • Finally i assume there would be no problem in using a de-coupling membrane before applying the floor tiles? ANSWER No problem at all
 
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O

Old Mod

So this company has absolutely no idea what it’s talking about, or what the industry standard is for Tiling to ufh.
To me it sounds more like for timber floors.

The advice I would give would be two fold.
1. Ask to see test results. :D
2. Speak with the TTA, and get their recommendations on the method statement that you have been presented with, hopefully also being able to give the name of the person you have been dealing with too.
From the text in the pdf, it appears to be badly translated English at best.
Every tiler in here knows that floating floors should not be tiled to, and that the minimum ply wood overlay method would specify a minimum of 15mm as laid down in British standards BS5385
And it is certainly not industry standard to loose lay it! Haha
 
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L

LM

Also another major concern is the ply being a fire hazard!
That has to be one of the most bizzare method statements I've ever seen, it's wrong on so many points.
The translation to english of such ridiculous advice is also terrible.
How can advice like this be allowed.
Lawyers would have a field day with this in the event of a claim.
@3_fall test results for the above would be very interesting indeed :D
 
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D

Dumbo

impish said:
It seems pretty clear too that ALL ply available now is completely unsuitable for tiling onto.
Years ago it would bond really well to cement based adhesive, but every time I see or hear of ply underlay it has always failed to bond.
Crazy.
Click to expand...
Does anybody know why that is . I think when they removed the carcinogenic stuff they removed the good stuff
 
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John Benton

John Benton

TF
Arms
2,211
1,138
Leeds
Clearly no idea whatsoever!!! Looks like they've use Google translate from Swahili to Pigeon English. It makes no sense at all.

Perhaps the individual who created the sequence of materials diagram was indeed a 'retro git' him or herself!!!
 
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J

Jonner

Firstly Many thanks; Marc, Andy, HM, ACT, Lee Mac, Impish, JCR & John for your time and comments, it really is greatly appreciated.

Following your feedback and my earlier discussion with Marc we are going to cancel the idea of an "overlay" underfloor heating system.
We in are in a lucky position to be installing the underfloor heating only on the ground floor in 2 rooms that connect to each other. Each room currently has a concrete floor. Please note the heating system is an Air Source Heat Pump with flow temperatures of about 35-40deg C.
So having done some more research we are now proposing to install underfloor heating with a screed, (either concrete or resin). We are then hoping to tile on the screed.
Do you think this would be the best approach and do you have and do's and dont's when considering this type of floor and tiling?
Any advice gratefully received. Thanks again for all your help so far.
Cheers Jon
 
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