Large format popped around edges

[One Day]

Anyone considered that with very large format tiles, the curing/drying (two different things which affect the other) can vary and affect curling of the tile?
I'm not saying I know it's a fact, but if adhesive cures at different rates and loses water at different rates underneath a large tile, it could potentially curl a tile???

I've been watching this thread from the off, and without a step by step on the OP's install, we're all just guessing.

 

[J Sid]

Doesn't the tile adhesive dry at different rates under all porcelain tiles? Much more noticeable under larger format tiles.
I sure we have all had to lift a tile which has been down a week or more and the adhesive in the middle of the tile still looks to have moisture in it compared to the edges.
Would this mean a 12mm porcelain tile would bend / curl …. I would be amazed.

 

[Waluigi]

Just me guessing but.........Being concave makes more sense with the edges coming up. Clips are used to pull edges down. Tiles try to revert back to their normal state when Heat is applied.

 

[Italy]

now you're going over ....
a porcelain tile does not fold
until you cut it and lose tension.
it is taught at elementary schools.

 

[J Sid]

I've pulled 900x900 tiles flat with clips in wet ufh before and never had a problem but that was on sand and cement screed and layed correctly.
If on a screed with a high moisture level and no ditra I could imagine the adhesive around the edge is constantly damp an not drying and sticking to the tile, tile edges becoming unstuck.

 

[Waluigi]

Anyone considered that with very large format tiles, the curing/drying (two different things which affect the other) can vary and affect curling of the tile?
I'm not saying I know it's a fact, but if adhesive cures at different rates and loses water at different rates underneath a large tile, it could potentially curl a tile???

I agree with your statement. Also throw in the heat to an adhesive that hasn’t cured and it reminds me of a bimetallic strip bending.

 

[Mark W Smith]

i agree with others that a 10mm seration only is insufficient for bonding a 12mm large format tile, I never tile directly to the ribs, always back butter the back of the tile but with large format always aerate the back of the tile, this will also help with the concern of levelling clips pulling the tile from the adhesive bed.

Tiling onto a gypsum screed with a cement based adhesive is something I don’t do either, I would have used a decoupling matting fixed down with a gypsum based adhesive first then cement based on top of matting.

Did you take note of the pot life of the adhesive and also the open tile as this could be something as simple as the adhesive skinning over or still being used from the bucket after recommended pot life.

Never used Norcros before and I can’t seem to download a data sheet on the adhesive you have used to find out pot life and open time ( did you check this before using?....if so did you adhere to these times?

2mm to 10mm bed depth doesn’t give me much
confidence either......I always like to use an adhesive that allows up to 15mm.......ultra SPES is my choice as maximum bed depth is 20mm not that you would bed out that much but just my preference you don’t need to be concerned with bed depth so much when laying large format onto a bad floor.

I think the fact you didn’t do a moisture test on the screed first could be a concern too.

Anyway I hope you get to the bottom of it and rectify the issue so you don’t have this problem again for future installations.

 

[Bill]

Never used Norcros before and I can’t seem to download a data sheet on the adhesive you have used to find out pot life and open time ( did you check this before using?....if so did you adhere to these times?

https://www.nxadh.co.uk/products/standard-set-flexible-s1-tile-adhesive-grey/

 

[Ajax123]

that the floor was wet when you lifted the floor protector gives you the answer. The floor was not dry. Whether this was from the screed (probably) or the adhesive or a combination is not really possible to say based on description so far. The cement based adhesive will have reacted with the sulphates in the screed causing a partial delamination as the tiles wanted to return to their original concave shape so all the pressure was on the edges. I have seen tis a few times in the past and in all cases the edge failure was followed by a general failure as the reaction will continue whilst the floor is higher than 0.5% moisture. also when the tiles are trafficked there is a lot of stress on the adhesive bond due to the tiles moving. Its a remove and replace I'm afraid.

Remove the tiles and treat the screed as if you had done nothing i.e. re sand it, check it for moisture properly and then retile using a gypsum based tile adhesive and back butter the tiles. I'm not sure though if the vertical stress on the adhesive due to the tiles wanting t curl will overcome the sheer strength of the adhesive or its bond with the screed.

 

[Time's Ran Out]

Apart from the moisture the adhesive used states suitable for anhydrate screeds but there is no rh readings on the packaging!