Need some advice on how to sort this common issue out. I had some tiles laid on my kitchen and hallway 3-4 yrs back. Tiles are 60x60 cream porcelain tiles laid ontop of flexible adhesive. The felixible adhesive is on top of Ditra matting which has been laid down with flexible adhesive on a concrete floor in which I had installed water UFH. The hallway does not have the UFH installed, it is just a concrete floor. 1-2 years after it was laid, I started to get cracking in between the tiles and decided to rake out the grout again and regrout with flexible grout (Mapei). I am starting to get the same thing again and have noticed that some of the tiles sound hollow when I tap them, (probably loose).

The advice I need is the following;
1) I plan to sort the loose tiles out by lifting them up, chiselling the adhesive away and applying fresh flexible adhesive and relaying them. Would this be ok? If not then please advise.

2) I plan to regrout the tiles for the 3rd time with flexible grout but have heard that there are other products on the market where you can add additives which will be better then the standard flexible grout. Is this true? I am looking for the best product so I don't have to do this again.

I'm not sure if the UFH is the cause of this as we only use it in the winter 5-10 times, and I had the Ditra matting laid as I was advised this would be the best thing for UFH before laying tiles.

Any advice would be great.

I was thinking about using BAL Wide joint grout with Admix GT1 for grouting the tiles. Would this be a good choice?

Have you used grout suitable for floors on the last two occasions?

There should not be a problem if correct materials have been used when there is a concrete sub floor. Could be you have a problem with the concrete slab or screed.

Is the mapei grout, grey???? by any chance. There are a lot of tilers who have trouble with the grey, patchey colouring, cracking and have even had the problem myself but not with any of their other colours.

Is your wife saturating the floor whilst cleaning?? may be better suited to having an epoxy grout.

There could be lots of possibles for the cause. the best option may be to get a pro tiler to have a look and advise. I mean a pro tiler and not a bathroom/kitchen basher.

If you remove the hollow sounding tiles, you'll find that the affected areas are dot / dabbed or at best not solid bed adhered to build up the 60x60 porc's, as you have UFH, air expands by upto 70% heated, the air pockets are creating movement under the tile, hence your grout cracking syndrome, as the grout is the weaker substance. relay affected areas with a solid bed of sticky. hope it helps

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Natural stone specialists mosaic, porcelain and ceramics

Why would it only happen every couple of years though???

That is what throws me and give me the impression it is the slab.

I doubt anybody that spec'd ditra would be the sort to dot and dab. There are a number of things it could be.

You say you had the wet ufh installed, how thick is the concrete, how long was it left to cure before tiling and was the ufh commissioned before tiling (i.e was it brought up to full temp then allowed to cool before tiling)

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Professional Kitchen & Bathroom Fitters | Master Painters and Decorators | Brighton & Hove

Colour.............that still doesn't add up with me though.

It was fine for two years after completion then cracked. Was re-grouted and now two years after that was done, it is happening again.

On the other hand, although I think it could be the slab/screed or even the clay lower down, that would crack tiles rather than just grout. One would assume.

It could be many things and without seeing it it's hard to say, the spec sounds ok. but there are many factors to take in to account as you know, where are the tiles placed that have debonded, how large is the floor, are there expansion joints.

Some problems don't show themselves for years then all of a sudden failures appear at increasing rates, could be down to installation, the weather, the way the floor is treated. There has to be a reason and the more info given will help eliminate causes

Reading back I don't know why I assumed the UFH was a wet system, it may well be matting laid over an old slab. The addy may not be suitable for UFH or the system was commissioned too soon after installation, if the issues are only slight then a good quality grout can hold the tiles in place and hide any failures until it can take no more

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Professional Kitchen & Bathroom Fitters | Master Painters and Decorators | Brighton & Hove

you say that, but if they came across a height issue, or levelling issue whilst fixing they may have taken the shortcut of dot / dabbing aswell? especially with 600x600

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Natural stone specialists mosaic, porcelain and ceramics

Thanks for the input guy's. Answer to your questions is:

1) If you remove the hollow sounding tiles, you'll find that the affected areas are dot / dabbed or at best not solid bed adhered
It wasn't dotted or dabbed as I was watching the tiler lay down the tiles.

2) You say you had the wet ufh installed, how thick is the concrete, how long was it left to cure before tiling and was the ufh commissioned before tiling (i.e was it brought up to full temp then allowed to cool before tiling)
The concrete is according to spec by the manufacturer. When the initial concrete was being laid the council inspector did ask me if I was having anything put ontop and I told him about the UFH. He stated to the builder to add 15-20mm insulation on top of the concrete being laid, clip the UFH to it and then add concrete (I think he stated 4-5inches minimum. I made sure it was as reqd. just for piece of mind), annoyed the builder as he had to dig down abit further to allow for the extra layer (gave him a couple of hundred for his troubles). It was left for 2-3wks before it was commissioned and worked fine with no problems. Tiling commenced about 2 months after.

3)you say that, but if they came across a height issue, or levelling issue whilst fixing they may have taken the shortcut of dot / dabbing aswell?
The floor was levelled out using a self levelling compound (fairly sure it was latex SLC)

4)Colour
It was white mapei flexible grout, will probably change it to Grey/Black as dirt gets into it too quickly and it's a b!tch to clean!

5)where are the tiles placed that have debonded, how large is the floor, are there expansion joints/Reading back I don't know why I assumed the UFH was a wet system
floor is approx. 40 sqm, the tiles that have debonded are in various areas. There are no expansion joints as it is laid on solid concrete (There is expansion joints on all edges/sides of the concrete as per spec). It is a wet system made by Nu heat

6)Have you used grout suitable for floors on the last two occasions?Is your wife saturating the floor whilst cleaning??
It was the same bags that were originally used (there was a big bag left over from the original install), thats why I'm now thinking going for a different mix (BAL Wide joint +GT1 ) so it will never re-occur, Wife's not saturating the floor as I'm the mug who gets roped into doing that chore! ;-)


I'm kinda inclined to thinking now that the bag might have been dodgy as that is the only common factor in all of this, hence my thinking of using a different mix as stated above.
Do you reckon this could be the cause? And using BAL Wide Joint with GT1 would be the best mix for this? The joints are approx 4-5mm wide. After the view on grey I would probably got for black

Point 6 is interesting..............even if the bag was fine in the first application it would be well and truely past its use by date for the second application. you can't keep open bags and use them a year or two later.

If you want to keep white grout, then use EPOXY as this will be easier to keep clean.

My view on the grey was just for Mapei..............Bal will be fine to use in grey.

Agree but it should be pointed out that I wouldn't advise epoxy grouts are applied by a novice, if you really do want to do it yourself, practice first! The other option is to seal the grout after which will add protection and make it easier to keep clean although this would not be as hard wearing as an epoxy

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Professional Kitchen & Bathroom Fitters | Master Painters and Decorators | Brighton & Hove

Thanks for that guy's. Will think about wether to use epoxy or not.
Just one question, would the epoxy grout be affected by expansion/contraction from the UFH? Also if I do decide not to go with epoxy would the Bal Wide joint with GT1 mix be a suitable alternative?

Epoxy is fine with UFH. Allow 48 hours after grouting and introduce heat gradually.

If you go with the epoxy route, then check the manufacturers instructions or call the tech dept for advice about turning on UFH.

Can't comment on the Bal as I normally use Nicobond products.

Cheers mate, will let you know how it turns out once I finished with it. Still deciding which route to go for.