Problems with Tiles Cracking with Underfloor heating

Minnie128

Hi all,

I am just after any advice or experience anyone has had with underfloor heating and ceramic tiles. Last year we had our bathroom replaced and it was all ripped out and redone. As there had been a leak underneath our old shower, the whole flooring was replaced with 25mm thick marine plywood.

We decided to use the warmup loose electrical wire and the guidance when using this product is to apply the primer to the flooring which our bathroom fitter followed. He then tiled the floor with ceramic tiles and at this stage we are uncertain if flexible adhesive was used or not. He did however, grout around the edges rather than using a flexible sealant.

Now what has happened is that there is now a line of three tiles in a row which have started to crack. And some of the wall tiles the grout has started to come away. We called the bathroom fitter back and he agreed to replace and re-grout the wall tiles, but felt that he wasn't to blame for the floor. He advised that we should get a surveyor to come and take a look at the floor as he felt it could have been subsidence. This is highly unlikely as there is no signs of subsidence in the property or outside and the house was built in the late 1970's.

The surveyors report states that there is no sign of subsidence and that the cracking of tiles maybe related to a solid masonry wall below and either side of this wall are the joists supporting the floor. The report states that as there is a total rigid backbone to the floor that as people walk across the top the tiles are then breaking and that this may have been prevented if 30mm thickness had been used (this was what the old flooring would have been) and or if a flexible adhesive/sealant had also been used.

Obviously the fitter is not very keen to rip up the floor as it is likely this will damage the underfloor heating and result in the whole floor and electrics needing to be replaced. The fitter is now saying that he thinks this isn't the cause and that it could be shrinkage due to the underfloor heating. Does anyone have any idea if this is possible and if there is anyway of proving this?

We really don't know what to do next and feel like we are going round in circles with this whilst the flooring is getting worse. Any advice will be most appreciated! Thanks.

TheCyclingProgrammer

Have you spoken to Warmup about whether it could be the cause? IMO I think your surveyor is on the right track.

Furts

Like any other poster I have to make the proviso of not having seen your floor. It sounds to me like your floor may not have been really suitable for tiling, and made worse by the decision to have ufh.

However, your installer has not put soft joints at the edges, which shows a lack of judgement, if not competence.

Couple this to whatever floor tile pattern has been laid. An expansion/contraction joint could have been formed directly above the solid wall. It sounds like this was not done.

As the existing floor was renewed the installer will have seen the solid wall, and seen the joists. Hence they will be fully aware of the bearings. This new floor could have been laid with a joint just like (I suspect) the old floor would have been. Consequently I again say this shows a lack of judgement, if not competence.

Hope this helps.

andyhop

I'd put money on it being the plywood

I've seen countless sheets of 25mm that have a excessive moisture content

When it shrinks it creates a straight line crack, this is on floors that are Herringboned and all edges sitting on 4x2 c16. Clean break on the tiles where it's pulled grade 5 porcelain in two. Tiles still stuck solid

When electric UFH fails it's usually down to poor fitting, it won't create straight lines more hazing and popping tiles

southcoastrgi

The addy should have been flexible & suitable for wooden floors & UFH not all of them are, also the heating shouldn't be turned on for at least 8 days after tiling

brightontraveller

Timber floor, UFH and tiles can certainly be a problematic mix, Timber is more prone to change with humidity and temperature etc you can try and counter with measuring moisture level in floor (prior tiling) , adding an insulator, using flexible adhesives, grouts, restricting temperature of UFH etc.

Assumed eliminated structural cause ( although manufactures don't recommend single skin plywood direct to joist then primer etc ) then most of the time its down to excessive moisture level in floor when tiled, not using flexible adhesive etc, adhesive insufficient time to cure correctly prior to using UFH, Subsequently not limiting UFH temperature, Hard to say which specific or infact if all are causing it at a guess because tiller stated subsidence to start (easy pass back to client) then when subsidence was eliminated its shrinkage that and not using correct adhesive grouts to start (or at least according to survey) I’d say there ability to lay tiles maybe fine but there knowledge of tiling with UFH and timber is either limited or they don’t care?

Not that its subsidence but Underfloor electric on timber most manufactures (the one you used among others) guidance would be wood floor, either insulator board or plywood /tilebacker board , primer, underfloor heating , flexible adhesive, tile etc not single skin plywood straight to joist then primer etc

http://www.warmup.eu/eu-dws-technical-flooring.phtml

http://www.floorheatingsystems.co.uk/underfloor-heating-help/

andyhop

southcoastrgi wrote: »

The addy should have been flexible & suitable for wooden floors & UFH not all of them are, also the heating shouldn't be turned on for at least 8 days after tiling

That's utter crock

Can be turned on once adhesive cured

Then slight increases over a period of weeks until you hit its max set point

If you go from cold to full heat you risk popping tiles

A single part adhesive would be fine but I always use a 2 part flex S2 adhesive just to be on the safe side

southcoastrgi

Oh dear wrong again I don't know why you bother arguing with me cause you are never right.

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andyhop

It's certainly not what DEVI tell you. Maybe if you have 100mm depth but not a 6mm screed and 6mm bed of adhesive

Bet you spot fix your tiles like you do your slabs.....

southcoastrgi

My pic was from the warmup installation instructions,

You don't need to spot fix just a squiggly line of pink grip & the jobs a goodun

hc25036

Had exactly this, although without the underfloor heating. Just a tiny movement of the joists or plywood can lead to cracking. We gave up after a couple of repairs and laid high-quality vinyl over the floor tiles (we had just enough room). The guys that advised us and laid the vinyl were major flooring experts and said we should never have been told that ceramic tiles were suitable on our floor.