Advice on tiling onto "overlay" underfloor heating

[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

 

[Flintstone]

What do you propose to use to bond the backer board to the foil? It’s come to light recently thay something in the aluminium breaks down cement based adhesives.

 

[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

 

[Flintstone]

Morning jon.
Personally I have never tiled onto one of these systems, I have managed to avoid so far and turned down a couple. Some on here will advise you better than I can.

 

[Spare Tool]

Far as I'm aware its all in the priming and putting a barrier between the aluminum and Portland cement, Imo a good coat of eco prime and grip followed by 10mm of a flexible self leveler would be the way to prep this type of ufh

 

[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

 

[Spare Tool]

Personally id stick with the same manufacturer for primer and self leveler, I only use ultra and Tile Master so can't comment on the BAL, but both TM and Ultra make a prime and grip primer and slc suitable..
And yes the slc is instead of the cement boards, will disperse the heat better

 

[Old Mod]

Let's start from the begging please, what brand of retro-fit ufh are you using Jon?

 

[Jonner]

Hi 3 Fall
Hetta Systems overlay system. see page 6 of below link

Link to UFH Brochure http://www.hettasystems.co.uk/ext/hetta_merchant_a5.pdf

 

[Old Mod]

Hi 3 Fall
Hetta Systems overlay system. see page 6 of below link

Link to UFH Brochure http://www.hettasystems.co.uk/ext/hetta_merchant_a5.pdf

Gimme a minute please.