Huge problem and sleepsless night ,opinions please

[pdmbathrooms]

Kinda new here, so hi to you all. I have been using Tops tiles flexi rapid set for years now and never had a problem ( i get a lot of work from them ,scratch each others backs ) Recent job was a 30 sq meter extension on a wooden floor with 600x600 porcelain floor tiles, builder had laid 6 mm ply and was told to bolt obviously, i was reliably informed he then relayed the floor with 18 mm ply, he then laid a electric heat mat and screeded over the top of it, made an arse of the screed lots of high and low points, anyway i then primed the screed with Bal SBR and tiled it which all turned out well.
Two months down the line and about half the tiles have popped in the central area , the tiles round the edges and those that are in the boundaries of the original building are all fine, the ones in the centre of the new extension have all popped. i Lifted a couple and could immediately tell that the ply had not been primed before screeding which the builder has now confirmed , i could lay the blame on this however when i lifted more tiles and i have noticed that while the tile adhesive has obviously been in contact with the tile (the whole area under the tile has the imprint of the back of the tile on it) ,the tile has lifted up clean with very little adhesive attached to it, any ideas why this would happen ? ive been tiling for nearly 15 years and never had a floor pop to date . When i chip away at the screed the ply underneath is very clean and intact. I'm not looking to apportion blame here but would really appreciate genuine thoughts and opinions on what has went wrong and suggestions on how to fix , thanks in advance guys/gals

 

[Qwerty]

Problem lies with UFH onto ply then levelled over. This will cause the wood to expand and contract and pop your tiles. Full rip out only real solution here

 

[pdmbathrooms]

Thanks for that , any thoughts on why the tiles lift clean ?also any time I have layed heating ive had to paint\prime the substrate with a primer supplied with the heating matt

 

[AliGage]

Take it we didnt back butter the tiles then?
Was it rapid set used? The adhesive is well bonded to the floor? What UFH was used?

 

[White Room]

How long was the ufh left before it was switched on...

 

[AliGage]

I take it the client was using the UFH until the point you were called in

 

[gamma38]

Loads of problems here i reckon, it did start with the prep but a bit of thermal shock sounds likely as well. As plan tec says though, timber substrate heated will expand and move a lot compared to what's on top of it, it was destined to fail really.

 

[radim]

i would bet money on thermal shock....

 

[Time's Ran Out]

Ok - so the Op knows - what causes thermal shock and how is it identified?

 

[pdmbathrooms]

Really appreciate all the input guys ,I used a flexi rapidset ,ufh was only installed two days before I tiled , not sure which brand to be honest , thr adhesive I have used has bonded well to the screed he put down but the screed itself lifts fairly easily off the ply

 

[AliGage]

Was the UFH put in the screed or rolled out on top. Im confused

 

[Qwerty]

I assumed he meant SLC?

 

[gamma38]

Just read the original and i'm confused also, slc or screed. I did get told about a new electric heat cable that does go in the actual screed not on the surface. Bit more info needed i reckon.

 

[The Legend; Phil Hobson RIP]

Ok - so the Op knows - what causes thermal shock and how is it

identified?

Good question John thermal shock is caused by heating being turned up to high to soon. Could be also related to ufh not being commisioned correctly,.

Usually tile comes clean from bed, with just a bit of residue from adhesive on tile.

 

[White Room]

Ok - so the Op knows - what causes thermal shock and how is it identified?

Thermal shock caused by unusually large stresses when two dissimilar materials are bonded together or are in close contact, the adhesive needs time for the moisture to remain for it to cure, any sudden heat to soon will cause the sudden loss of moisture and weaken the adhesive to point which it could become crumbly and lose it's strength.

 

[One Day]

Sensible suggestions so far.
I've seen poor bonds on porcelain (while of on substrate) caused by tiles being stored outside in very cold temperatures.
Think the chilled tile doesn't form a good bond with the rapidset - not long enough for the reaction to warm the porcelain, whereas the substrate is warm and porous enough.
Just a suggestion....

 

[pdmbathrooms]

He layed the ply ,layed the heating mat then put slc over it as advised on the instructions , he is in the building trade so he wanted to do as much himself as he could , the thermal shock theory sounds the most plausible , the problem I now have is he reakons its my fault however I believe its all been prepped wrong .I made the mistake of presuming he knew what he was doing , I came in and saw a levelled floor and used products that are reliable , not sure how to approach it all

 

[Diamond Pool Finishers]

[video=youtube;v5wobrRYiiI]https://www.youtube.com/watch?v=v5wobrRYiiI[/video] And also remember that diffrent materials expand /contract at different rates !! witch causes problems in different layers applied to the substrate

 

[White Room]

Sensible suggestions so far.
I've seen poor bonds on porcelain (while of on substrate) caused by tiles being stored outside in very cold temperatures.
Think the chilled tile doesn't form a good bond with the rapidset - not long enough for the reaction to warm the porcelain, whereas the substrate is warm and porous enough.
Just a suggestion....

Again thats thermal shock due to the different temperatures, all tiles should be bought in for at least 24 hours to be climatized to the working areas.

 

[Diamond Pool Finishers]

And in response to TJ question you need to find -out the coefficient of every material in all the layers and make sure they are compatible like this or consult a set of pre-worked tables [video=youtube;5ud3kX9IVW0]https://www.youtube.com/watch?v=5ud3kX9IVW0[/video]

 

[Stef]

The 1st thing I notice is that the tiles haven't been back buttered,
Very little bond on back of tile.
Onto ply, even though it's been overboarded with ply I would still try & stick a backer board down.

 

[beanz]

How long before the underfloor heating was turned on? Lack of back buttering could also be a contender here...

 

[Rookery]

Just my opinion but I'd say:
1. Too much deflection in middle of floor.
2. Tiles not back skimmed.
3. UFH switched on too soon and not warmed & cooled gradually.
I wouldnt have tiled to ply either.

 

[radim]

two different materials expand in different way when heated (tile and adhesive) and this may lead to crack. So when tile debond from adhesive it is actually horizontal crack. IMO