Tiles cracking where screed slabs meet (wet underfloor heating)

[Johneb]

Hi all,

Following some excellent advice from you in 2012, I successfully laid approximately 40 sq m of ceramic floor tiles in our new kitchen, garden room and granny flat. All was fine for a while, but then the tiles cracked across the opening between the garden room and kitchen, a distance of slightly less than 2m. Both areas have wet underfloor heating (on separate circuits), set in approx 100mm of screed topped with levelling compound. The crack is where the two slabs of screed meet - they were laid at different times. The tiles are ceramic, 400mm sq.

Before laying the tiles, I consulted the underfloor heating manufacturer and was told there was no need for a decoupling membrane in this location - it should be fine so long as I used flexible adhesive and grout.

I have delayed replacing the tiles for over 12 months to allow for any settlement of the screed slabs and to allow the heating to be fully 'run in'. I now want to replace the cracked tiles and should be very grateful for any tips on how to lay them to minimise the risk of them cracking again

Finally, what is the best way to remove the line of old tiles without damaging those on either side? I have been told to crack them with a hammer, but again would appreciate professional advice.

Cheers, John

 

[Ajax123]

There should have been a joint in the screed which should have bee reflected through the tiles. Decoupling would not have helped

 

[widler]

No expansion joint ?

 

[Johneb]

Thanks Ajax123 and widler.

There was a line of foam edge insulation about 8mm thick between the screed slabs, although I seem to recall the builder bridged this with levelling compound. Didn't worry about it at the time as wasn't between screed slab and an exterior wall..................

 

[mike1979]

Deffo should of had an expansion joint there

 

[Brian the Tile]

its too late now but tiles should have been laid either sie of expantion joint,to get them up hit in the middle of the tile with your hammer and work outwards very carefully

 

[Houston]

needed expansion. I would contact builder

 

[WetSaw]

Use a multitool to remove the grout first before carefully breaking the tiles with hammer and small bolster, should prevent the joining tiles getting damaged.

 

[SJPurdy]

as pdc. remove surrounding grout first, using multitool, angle grinder or manual grout rake. Then you should be able to take out the unwanted tiles without chipping the adjoining tiles you want to keep.

 

[Old Mod]

Personally for me what I find most successful and low risk, as long as a bit of dust isn't a big problem, is to cut directly into tile on inside edge of grout line. I find the risk to adjoining tiles becomes minimal. But I prefer to work from outside edge inward. This means you're always working away from the tiles u want to preserve. A lot of grout tends to fall away quite easily. A way of minimising dust is to have the blade on the right side of the grinder (effectively what most would consider upside down) as u cut and draw the machine towards u, at the same time another person can track your movement with a vacuum hose, because the dust will go away from u instead of toward u, this will reduce the mess 10 fold.

 

[WetSaw]

And obviously be careful not to go too deep and damage your ufh!!!