Advice on tiling onto "overlay" underfloor heating

[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.

Thanks for the advise re getting a method statement from hetta i will contact them and let you know what comes back.

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.

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

 

[Spare Tool]

Zoinks...6mm ply
Wonder if maybe nomoreply and their dedicated tube adhesive might be better than a cement based adhesive?

 

[hmtiling]

6mm ply overlay. That'll do it

 

[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

 

[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

 

[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.
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

 

[Flintstone]

That’s an absolute embarrassment

 

[Spare Tool]

And we wonder why we end up making it up as we go along...

 

[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

 

[LM]

Adhesive and 'grout' layer???? what's that all about??

 

[One Day]

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.

 

[Dumbo]

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.

Does anybody know why that is . I think when they removed the carcinogenic stuff they removed the good stuff

 

[LM]

FG1 - Plywood (High Quality 5.5mm Flooring Grade Plywood) - http://fg1-plywood.co.uk/

This may be of interest to some of you and is being pushed a lot but for tiling there's better options in backer boards.

 

[John Benton]

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!!!

 

[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