Tiling over overfloor heating system - Wundafloor - TilersForums.com

[Shinyshiny054]

Hello,
I’m new to tiling and to forums so my apologies for both if there are any etiquette failures!

I’ve scoured the internet and can’t find any tangible advice on tiling on over overfloor heating. We installed the Wundafloor EPS 400 system ourselves (other half and I) and are concerned about the loops which sit proud of the boards. I called Wundafloor and the advice was to tape the loops down. We’d already done this but pushing on the loops with a foot still allowed a fair amount of bounce. We were told that Granfix ultimate flex with ultra prime it would provide enough protection to the tiles from th bounce. We are doing an entire ground floor so naturally I’m concerned being a) a complete novice and b) that we lay it all and the tiles crack or lift.

Has anyone laid tiles over such a system and what are your recommendations? Will we be ok with the adhesive only, will it absorb the bounce as we’ve been advised? We have limited height to which we can tile, but we’re planning on a 10mm adhesive layer (though have been recommended 6mm by Wundafloor)

Tiles are porcelain 605x605mm

Many thanks

Gill

 

[Lee@emctiles]

Hi Gill, have you tried calling Granfix to check this procedure is adequate?

From personal experience, my method of these type of UFH systems i would recommend laying a flexible levelling compound.

a quick call to Granfix might be a good idea 01827 871871

 

[Flintstone]

There are a few types of these systems can you tell us the set up please. Solid floor? Floating insulation with pipes in? Stuck down? Made of gypsum? Got foil on the face? Timber floor?

 

[Shinyshiny054]

The type of floor is concrete base (that house was built on), stuck down panels with foil face and pipes pressed in (pretty tight loops which resulted in lifting pipe). Part of the floor, an extension, is suspended floor with wood chipboard. The same panels were used here, we’ll use an expansion gap so there’s no tiles spanning existing house and new. Have attached a photo of the system taken while we were laying it, it’s too dark down there now to photograph the level of lift I’m taking about but possibly a few mm

 

[Flintstone]

Personally I wouldn’t tile it. You cant tile to the foil surface or use a cement based product. Perhaps @3_fall might be able to advise better

 

[Shinyshiny054]

Personally I wouldn’t tile it. You cant tile to the foil surface or use a cement based product. Perhaps @3_fall might be able to advise better

Thanks for getting back to me. The instructions from Wundafloor specifically state you can tile it, using a primer, and we bought the system on the premise that we could. I called them about the bounce and they were confident in the fact it can be tiled. I really hope it is the case because it’s all primed and ready to go as soon as we have a child free day!

 

[Flintstone]

I’d hold your horses before you get the correct info. Read this link and follow the links within it and tell me what you think

Preperation - Advice on tiling onto "overlay" underfloor heating - https://www.tilersforums.com/threads/advice-on-tiling-onto-overlay-underfloor-heating.84747/#post-884476

 

[Old Mod]

Hey Gill,
Andy’s (local) is quite correct, this type of system is subject to a high rate of failure because of incorrect preparation generally.
It’s not a product I would tile, these systems are primarily aimed at the laminate and soft flooring finishes, but they do state the 400 series is suitable for a hard tile finish.
If I could be convinced totile one of the systems, I would have to insist on this product being used.

https://www.wundatrade.co.uk/shop/home/accessories/tools-accessories-2/4mm-backer-board/

It’s a 4mm board designed to cover the Wundafloor And give a tillable substrate. Although in their literature they state it’s an optional extra, I would suggest don’t even think of Tiling it without it.
It creates a barrier between the Aluminium and cement based adhesives. And it’s far more effective than any primer they suggest.
In essence, the cement adhesive can react with the Aluminium and produce hydrogen gas and cause the adhesive to become weak and fail.
That’s based on research undertaken by myself and a colleague.
Please don’t think that ufh or adhesive companies will substantiate that, cos they won’t, why would they.
Do your own research, it’s there to be found quite readily.
(Reaction between Aluminium and Portland cement)
So as you’ve made your investment, I would strongly suggest the use of the above product.
Still prime as suggested and adhere the boards how they dictate, then tile it.
I would ask them for a ‘method statement’ to be emailed to you, and as long as you follow the instruction to the letter, that’ll be as safe an install as you can manage.
Are you tiling it yourself or do you intend to hire a fixer?
As far as your adhesive bed is concerned, a 10mm notch trowel will produce an approximate 3mm solid bed of adhesive.
Make sure that you skim the back of the tile with a thin layer of adhesive with the flat edge of your trowel prior to bedding it in to the adhesive. This will improve bond strength by 50%
It does sound like a mammoth task for a diy installation I must admit.

 

[Flintstone]

Good post. I’ve not seen those boards before, what are you supposed to stick them down with ?

 

[Shinyshiny054]

Thanks Localtiler and 3_fall for your responses.

If we coated with 2 or 3 coats of the primer, could we still be in hot water with the reaction between the aluminium and the adhesive?

If we were to go with the backer boards, will this help with the ‘bounce’ described with the pipes which don’t quite fit snug into the loops. The advice we were given is to tape down the loops, but they still move which makes me think that they’re weak spots waiting to happen once adhesive and tiles are on (ie air space under the loops). That was my original concern but now it’s grown arms and legs!

Thank you for taking the time to answer, it is a bit of an extreme diy I must admit...