Tiling over overfloor heating system - Wundafloor

[Shinyshiny054]

@Localtiler they’re stuck with a spray adhesive that was supplied by Wundafloor. Seems to have stuck them pretty fast - we made a mistake with one and it destroyed it ripping it back up once dry!

 

[Old Mod]

One part of their installation process states you can loose lay the boards, under no circumstance do this. They MUST be adhered to the eps boards.
As to whether it will stop the pipes from lifting, I would only be guessing.
Are you able to charge the system yet?
If so, pressurise it to 5-6 bar cold and see how they lay then.
The reason I say 5-6bar is because this will approximately mimic the expansion of the system when hot at 1-2bar when operating.
If the water weight holds them down, then with the backer board on top, it may well suffice.
I can’t confidently comment on ultra’s msp primer (multi surface primer) being sufficient to give you a successful install.
I could suggest that you contact our sponsor Isomat, there is a link below this thread, speak with Marek and ask if their primer Supergrund is suitable for use on this Aluminium system. The reason I suggest that particular primer is because it is resin based as opposed to acrylic or sbr based primers, and hopefully may be more resilient.
And then you could latex over the boards giving you a substantial increase in weight over the pipes. That is pure conjecture on my part tho, but Marek will contact his R&D department for you and give an unbiased opinion.
Tell him Marc from the Forum sent you.
Their technical backup is very good and they will stand by their products.
Other than that Gill, that’s about as much advice I can put your way I’m afraid.

 

[Shinyshiny054]

One part of their installation process states you can loose lay the boards, under no circumstance do this. They MUST be adhered to the eps boards.
As to whether it will stop the pipes from lifting, I would only be guessing.
Are you able to charge the system yet?
If so, pressurise it to 5-6 bar cold and see how they lay then.
The reason I say 5-6bar is because this will approximately mimic the expansion of the system when hot at 1-2bar when operating.
If the water weight holds them down, then with the backer board on top, it may well suffice.
I can’t confidently comment on ultra’s msp primer (multi surface primer) being sufficient to give you a successful install.
I could suggest that you contact our sponsor Isomat, there is a link below this thread, speak with Marek and ask if their primer Supergrund is suitable for use on this Aluminium system. The reason I suggest that particular primer is because it is resin based as opposed to acrylic or sbr based primers, and hopefully may be more resilient.
And then you could latex over the boards giving you a substantial increase in weight over the pipes. That is pure conjecture on my part tho, but Marek will contact his R&D department for you and give an unbiased opinion.
Tell him Marc from the Forum sent you.
Their technical backup is very good and they will stand by their products.
Other than that Gill, that’s about as much advice I can put your way I’m afraid.

If anything @3_fall the pipes seem to ‘tense up’ when we run the system and lift higher than when off! Thanks for the advice, it’s been very helpful. I will email Wunda and ask for a method statement and see if I can get any further advice based on your recommendations. ☺️

 

[Old Mod]

If anything @3_fall the pipes seem to ‘tense up’ when we run the system and lift higher than when off! Thanks for the advice, it’s been very helpful. I will email Wunda and ask for a method statement and see if I can get any further advice based on your recommendations. ☺️

Daft question hopefully, did you run the pipes out correctly?
By that I mean unroll, not just lay them down off the coil.
Does that make sense?
Imagine a roll of cable or hosepipe, if you correctly unroll them they don’t twist.
If you lay out the coils to the side for example, you get unnatural twists in the cable or hosepipe.
I’m only guessing obviously, but I can say I’ve not heard of the problem of the pipes lifting free of the boards, sounds like they are twisted to me, and when you pressurise the system it emphasises the twist causing them to lift.
Like I say, it’s just a guess.

 

[Shinyshiny054]

Daft question hopefully, did you run the pipes out correctly?
By that I mean unroll, not just lay them down off the coil.
Does that make sense?
Imagine a roll of cable or hosepipe, if you correctly unroll them they don’t twist.
If you lay out the coils to the side for example, you get unnatural twists in the cable or hosepipe.
I’m only guessing obviously, but I can say I’ve not heard of the problem of the pipes lifting free of the boards, sounds like they are twisted to me, and when you pressurise the system it emphasises the twist causing them to lift.
Like I say, it’s just a guess.

I know what you mean, we tried to lay them in following the turns of the roll as much as possible, probably why some are better than others. We’ve had some luck scraping out the polystyrene under the loops and that seems to help keep them down, there are a lot of loops to get through though.

I have emailed them with all the questions I have and points you have raised so I have something in writing. OH advises me that they referred him to their brochure when he emailed questions though, and attached a PDF We’ll see what comes back from them this time

 

[Shinyshiny054]

Ok so I called and spoke to Alan, Tech Support for Granfix/prime it. He advised that a neat 100% coverage, single coat of Ultra Prime It is sufficient in creating a seal between the aluminium and adhesive preventing the chemical reaction mentioned above.

We had used aluminium tape as per advice from Wundafloor to stick down pipes which had a bit of bounce at the loop but were concerned that the prime it wasn’t sticking properly. He agreed that there is an issue with aluminium tape and to remove all of this, instead using an alkaline resistant mesh (Skrim) tape to stick down any problem spots, the benefit being the adhesive can be pressed through it and around the pipes. The weight of the adhesive/tile should prevent any issues when dry.

He advised 6mm notched trowel gives 5mm bed thickness which will be sufficient together with back buttering of tile and in filling the joints and pipe runs with adhesive. Can anyone recommend a trowel for this? We overestimated and have a significantly higher notch.

 

[Dumbo]

A 6mm notch trowel will not give a 3mm bed depth as when you use the trowel you hold at about 45 degrees to the floor therefore the vertical height of your ribs are approximately 7mm . So when you slide your tile on the ribs to collapse the ribs to get full coverage on the tile you will get a bed thickness of about 3.5 mm . It's all to do with Pythagoras and his theory .

 

[Shinyshiny054]

A 6mm notch trowel will not give a 3mm bed depth as when you use the trowel you hold at about 45 degrees to the floor therefore the vertical height of your ribs are approximately 7mm . So when you slide your tile on the ribs to collapse the ribs to get full coverage on the tile you will get a bed thickness of about 3.5 mm . It's all to do with Pythagoras and his theory .

@jcrtiling thanks for your reply. I thought that the recommendation sounded a little off given the tables of advice I’d seen online.

What would you recommend trowel wise?

Gill

 

[Dumbo]

I wouldn't tile straight on the pipes . But I would use a large format trowel 20mm wide 15 mm deep . Get granfix to email you what they are telling you about the primer see if they are prepared to put it in writing .

 

[Shinyshiny054]

Yes, I have it all in writing from Wundafloor. The Granfix rep said that anything over 10mm is too deep and will cause issues with drying and contracting and cracking etc. Being a complete novice I have nothing to go on but advice I find online with regards to adhesive depth etc. I’d be keen to get a tiler to do it for me if we had the money and thought we could find someone competent that would take it on. As far as I can see no one wants to do it and I can find little evidence of anyone that has, and I now see why. Too late however, heating system laid and tiles, adhesive and primer all bought.

Just dealing with Wundafloor and Granfix over issues with the primer adhering to aluminium tape... :-(