What went wrong...?

[Ajax123]

I think laitance is the problem here
i have seen exactly the same problem on 150m2 of granite with ufh
the floor was not scrabbled,laitance removed
it was exactly as you say,wet underneath and no adhesion to sub floor
white patchy areas,chalky its laitance

What you are describing does not sound like Laitance. It sounds more like segregation which is a screed defect. You should not scabble screeds. They should be mechanically abraded which usually means sanding.

 

[zoemac]

Thanks folks - it looks like possibly the floor was still damp despite having 2.5 months to dry some of which with heater and some of which with under floor heating commissioned. Also sounds like SBR could have been too thick and formed a skin.

Given the info from the screed supplier and the way the floor was prepped I just can't see that it laitance (but I could be wrong). It seems more likely that despite the SBR a reaction between the gypsum screed and the cement adhesive occurred which is why the adhesive seems really powdery and brittle.

Does that sound right to people?

Guess I just have to suck it up - unless anyone has any other suggestions?

So the plan of action would be - take up all the tiles, run the underfloor heating full belt for a bit to ensure it is super dry and then prep and seal the floor again and relay new tiles with a gypsum tile adhesive.

What do you think?

Can't afford to do this at the moment - so will be living with a cracked floor for a while. But at least I know what I now need to do

 

[Ajax123]

If you have run the heating for a couple of days on low then it has not been properly comissioned.
the correct procedure takes two to thee weeks.

this might help http://www.gypsol.co.uk/4_Underfloor_heating.pdf

 

[Ajax123]

If this was done by your builder or by a tiler then they should be footing at least some of the bill....

 

[zoemac]

No was left to dry for a while - probably 2 weeks and then was run on low for a short while and then underfloor heating not used till November

 

[zoemac]

Thanks Alun - the problem is proving anything - I guess I could blame the tile shop as I described exactly what I needed and they recommeneded SBR + cement adhesive rather than a gypsum adhesive. I could blame by builder who also did the tiling - was the SBR applied to thickly, was the floor dry enough to be tiled. I could blame the screed people - was there a fault with the screed? But how do I actually prove what the problem was and who was at fault? It is going to cost me at least £3500 to put right - money the I don't have right now - but I can't see the tile shop, builder or screed company volunteering to contribute.

 

[The Legend; Phil Hobson RIP]

All of the above sounds familiar. Nice to see Neal (Sir ramic) posting, hope you are well mate.

 

[Mr Tiler]

There's a good chance it was not dry. Natural drying would need around 20 degrees and 60% rh. The choice of adhesive puts you at risk and whilst SBR can be used it is sensitive to moisture as well. Sanding the floor to remove Laitance and any other surface detritus is essential for correct preparation. If the tiles are coming up clean it is a printer failure as that is the bit that is supposed to stick to the screed and the adhesive sticks to that in turn. You will need to lift the tiles and replace them. I would use a gypsum based adhesive. There are loads about and they are no more expensive than cement based these days.

you know your stuff mate

 

[Andy Allen]

If the builder tiled the floor then imo he should foot the bill to replace it.
These screeds are notoriously difficult to get right and should only have been tiled by an experienced tiler.

 

[SJPurdy]

I suspect that this problem is happening to many other people. Other people who are about to have tiling carried out and are doing a bit of research will be helped to make better decisions after reading this post and the helpful advice and links given.

 

[CJ]

Local to me is a large 5 bed bungalow, that was having a small extension to the dining room. This bungalow is totally tiled. Extension was finished, and when everything was done, I had to extend the original tiling. This place had the older Anhydrate screed when built about 20 years or so........ALL the tiled floors are floating. The whole place has debonded.........it's like walking on a thin sheet of suspended ply. I had to lift a few damaged tiles in this extension, and didn't need any tools at all. The laitence had not been removed AT all. Cement solid on back of tiles.......floor totally clean.....but dusty.

It would cost thousands to put right now..........rough guess, about a 90m. I'm still waiting on that job.

This was also done by the original builder, who assured the guy "he knew wot he was doing"

Obviously NOT.

 

[Dash J]

What you are describing does not sound like Laitance. It sounds more like segregation which is a screed defect. You should not scabble screeds. They should be mechanically abraded which usually means sanding.

When I say scabbled that's what I mean alan,mechanically sanded
sorry for confusion,my words are not the greatest sometimes,got the two mixed up

 

[stusgsx]

There's no way I would think about tiling this type of screed until it's been tested and tested again. The one I have just completed was down for 6 months or so and I used gypsum addy and still worried!

 

[AliGage]

I don't know an awful lot about these screeds so won't really comment. However, it sounds like there may have been a few errors. Leaving latence to ither guts to advise on, the picture you show once the screed is primed looks to me like the SBR was applied heavy and undiluted. Anyone else?

 

[John Benton]

Going back approx. a year I was doing a couple of bathrooms for a customer when his neighbour came round and asked me to look at a problem with his newly laid floor in the large kitchen\diner extension had just been built.

Tiles were lifting in the same way yours are. When I asked how the floor heating was commissioned he looked at me as if I'd called him a Man U fan. The tiles had been fixed before the floor was full dry. This was the result of not having a fully dry floor.


The green is the primer that had lifted from the screed in the same way yours has!

The result being that the kitchen had to be removed, 90m of tiles skipped and re-fixed again. All this was done at the builders expense, he held his hands up and paid for it all (quite a reputable local builder btw).

Good luck but I suspect the whole floor will have to come up, and I don't think anyone will hold their hands up and take responsibility by the sound of things.