Green Building Forum - Tiles over underfloor heating are lifting- what to do next ?

Tiles over underfloor heating are lifting- what to do next ?

Greenlady — Sat, 01 Jul 2023 07:25:41 +0100

Tiles are coming loose approx 10 years after wet underfloor heating put over a suspended floor . We have now lifted the majority exposing adhesive up to 2-3 cm deep in parts ( floor levelling was carried out but clearly not enough ) , my question is - should we remove the adhesive ( incidentally the tiles came off clean)or can we re-tile over the top.?
How should we prepare the floor before getting a professional tiler in ?

Owing to the cost we are having to do all the labouring jobs ourself before getting a professional tiler in to re-tile .

Tiles over underfloor heating are lifting- what to do next ?

cjard — Sat, 01 Jul 2023 07:30:42 +0100

Pics would help. Post from a phone and choose "take photo" when hitting "choose file". To get the "choose file" button to appear one must log in at the top left of the page, not use the user/pass boxes about the reply area

Tiles over underfloor heating are lifting- what to do next ?

Peter_in_Hungary — Sat, 01 Jul 2023 07:57:12 +0100

If the adhesive is stable and not breaking up or flakey and given that the tiles came up clean I don't see any advantage in removing the adhesive. It sounds like a failure of the tiles to adhere to the adhesive.

I would talk to your tiler before you do anything and be guided by what he says as he will be the one who will need to do a job that has some level of guarantee.

If some of the tiles stayed down it may be difficult to relay the loose ones without a level difference. Lifting any still stuck may (will) result in broken tiles - do you have any replacements?

Tiles over underfloor heating are lifting- what to do next ?

Greenlady — Sat, 01 Jul 2023 12:17:21 +0100

see file attached

Tiles over underfloor heating are lifting- what to do next ?

GreenPaddy — Sat, 01 Jul 2023 13:06:34 +0100

Suspended floors and tiles can give problems, with the subfloor flexing, and so the rigid layers separating/cracking. Did the grout start to crack and lift, then the tiles? Flexible adhesive and flexible grout all help, but in my experience, they give problems.

That seems a lot of adhesive to use (visually and your description of 20-30mm). Not sure what the floor buildup is with joists, UFH pipes, screed, boards, self level, or whatever. If you can describe that, it might also help?

Are we distant cousins, by any chance? GreenPaddy

Tiles over underfloor heating are lifting- what to do next ?

owlman — Sat, 01 Jul 2023 14:12:41 +0100

As Green Paddy says the fundamental problem is is laying tiles on suspended floors. It can be mitigated by first laying a decoupling membrane. This interlayer acts to absorb stresses caused by movement of differing materials.

I've laid 15mm marble tiles on a floating membrane over a suspended floor, but first I ripped up the T&G floor, put props at intervals under the joists onto the site concrete, I insulated and replaced it with 22mm plywood. The membrane was then floated onto the ply and thinly screeded before laying the tiles. There have been no problems since, but no UFH.
If it were mine I'd start again, not I guess, what you want to hear..

Tiles over underfloor heating are lifting- what to do next ?

Peter_in_Hungary — Sat, 01 Jul 2023 15:00:15 +0100

Having seen the picture I agree with Owlman

Posted By: owlmanIf it were mine I'd start again, not I guess, what you want to hear..

Replacing with tiles will probably result in the same again unless you can ensure no movement in the floor - very difficult - consider what owlman did !

Do you need tiles ?

Notwithstanding the cracks in the adhesive, if it is stuck to whatever is under it then go over with self levelling compound (cement based product to fill unevenness in solid floors) and then put down ckick-fit laminated flooring designed for bathrooms. This is a high density flooring which will probably transmit heat better than a low density floor. (it nicely blunts of your TCT saw blade) All of this is DIY-able............Just a thoght

Tiles over underfloor heating are lifting- what to do next ?

Mike1 — Sat, 01 Jul 2023 15:17:35 +0100

Those look suspiciously like cracks in the photo. If so, I'd take it up and start again too, and would also use a decoupling membrane over the top of a self-levelling compound. Make sure that the compound is suitable for use on a timber substrate (assuming that's what you have), and that all products are flexible and suitable for use with underfloor heating (which will mean paying a premium).

Alternatively you could use a flooring other than tiles. If the subfloor is obviously flexing, this might be the only suitable solution, short of strengthening it.

Tiles over underfloor heating are lifting- what to do next ?

cjard — Sat, 01 Jul 2023 21:15:05 +0100

It's a little blurred but it does look like there is a decoupling membrane under that adhesive (hole on adhesive, bottom center. Looks like dural durabase

Tiles over underfloor heating are lifting- what to do next ?

cjard — Sun, 02 Jul 2023 06:53:12 +0100

My thoughts similar to Peter's; smooth it out with SLC and put LVT down :)

Tiles over underfloor heating are lifting- what to do next ?

Greenlady — Mon, 03 Jul 2023 18:16:45 +0100

Thanks for all your comments so far, to confirm the current floor layers.
We have NuHeat ufh laid in their supplied cement boards, which were then screeded over before the decoupling membrane was laid on top. Then we used Mapei c2 flexible adhesive sometimes requiring 30mm of adhesive unfortunately in places but only 6 to 10mm in others.
Could and should we have gone over the membrane with more self levelling compound or would that have rendered it useless, I assume the leveling needed doing over the screed.

Tiles over underfloor heating are lifting- what to do next ?

Peter_in_Hungary — Mon, 03 Jul 2023 19:03:37 +0100

Levelling is only needed if it is not level or full of holes. I would expect screed laid over cement board would not (should not) need levelling.
Never mind the past - you have to deal with what you have.
Ripping out and starting again is the last choice.
See how level the floor is. self levelling compound does that, if you have 2" difference one side to the other then you will get 2" of compound onb one side - very expensive so in that case you have to use a float to fill the gaps rather than create a sprit level floor. (assuming you are happy with any slope you have). I recall that the click fit flooring can cope with 3mm/M dip (or hill) so that would be your target if you go that way.
In your place I would abandon the tiles and go for an alternative floor as suggested above.

Tiles over underfloor heating are lifting- what to do next ?

revor — Mon, 03 Jul 2023 19:14:43 +0100

Posted By: GreenladyCould and should we have gone over the membrane with more self levelling compound or would that have rendered it useless, I assume the leveling needed doing over the screed.

No the membrane is designed to only have a fairly thin layer of adhesive between it and the screed below. ( If memory is correct 3 to 6 mm) In an ideal world the floor should have been levelled before fitting the UFH and failing that the overlaying screed should have been installed level. I had horrendous problems with a screeding company not laying the conventional screed level. I spent a week on my hands and knees with a concrete planer planing off the high points otherwise we would have had a result similar to yours as the tiler would be starting at the highest point as the reference, and having a thicker bed at the low points to get a level floor.

Tiles over underfloor heating are lifting- what to do next ?

Greenlady — Tue, 04 Jul 2023 20:15:00 +0100

Having the whole of the ground floor under floor heated and tiled over we definitely need to keep the tiles. So there are not many options, correct me but they would be:
<1> remove all the adhesive and decoupling layer and bring level higher with self-levelling compound then fit new or refit dural membrane.
<2> remove some adhesive day 10mm then self level to close gaps and maybe add 4mm on top then use 6mm adhesive to bring back up to original level so that all doors etc do not need rework.

Tiles over underfloor heating are lifting- what to do next ?

Greenlady — Tue, 04 Jul 2023 20:17:36 +0100

<3> remove all adhesive then pour levelling over decoupling membrane then fit another decoupling membrane on top then finally adhesive and tiles