Tiles coming up, cracks, and hollow points

[One Day]

can I insist they redo the tiles or would these incorrectly laid tiles not be considered a defect until they actually crack?

They are all going to come loose, sooner or later. As for a way forward, if your contractor plays hardball, I'd suggest a Tile Association report accompanied by a solicitors strongly worded letter.
The job is sub-standard and you paid for "due care and attention".

 

[One Day]

I always thought you needed S1 adhesive for underfloor heating.
Could be wrong though.

I will always choose minimum S1, but many manufacturers will be happy with less.
It's all down to the amounts and types of polymer I suppose.

 

[DazedConfused]

Still, I think any adhesive would have struggled to stick given that there was so much air between the tiles and the substrate!

this is what concerns me. if the cost of the tiles/adhesive/labour was X, can I refuse to pay the full amount until the redo it to my satisfaction or at least a higher standard?

my main problem to be honest is that my rather expensive kitchen and bar unit has been built upon these suspect tiles.

 

[Boggs]

I use Tilemaster Ultimate S2 on all my floors, timber or screed, heated or not.

 

[acaciaguy]

I would use s1. S2 used with a correct overall method should be better than than that

 

[One Day]

this is what concerns me. if the cost of the tiles/adhesive/labour was X, can I refuse to pay the full amount until the redo it to my satisfaction or at least a higher standard?

my main problem to be honest is that my rather expensive kitchen and bar unit has been built upon these suspect tiles.

If you've not paid in full, then definitely don't!
I am currently working with a customer who has exactly the same problem, only she paid in full; then they all failed, then the company went bust!

 

[One Day]

I use Tilemaster Ultimate S2 on all my floors, timber or screed, heated or not.

Ultimate for a reason! Good choice, even if a bit "icky" to work with.
Look out for Magix S2...

 

[acaciaguy]

Don’t pay. Let them do the chasing. Give you them solid reasons for you being unhappy. Be honest

 

[DazedConfused]

Tile Association report

https://www.tiles.org.uk/services/technical-inspections/

blimey, at 120sqM of tiles this could get expensive. I will give them a call tomorrow but I presume I can't ask them to just inspect a small section of the floor area!

 

[Flintstone]

I'm almost certain that's not anhydrite looking at the photos. I put this down to installer error mainly, and as impish has said, that adhesive is poor quality and debatable weather it's suitable.

 

[acaciaguy]

To start With don’t pay. Personally I would of go around and pull up tiles randomly. They will all be same. Then get contractor in and let him pick some. Show him the bad work. So sorry you are in this situation

 

[One Day]

https://www.The Tile Association/services/technical-inspections/

blimey, at 120sqM of tiles this could get expensive. I will give them a call tomorrow but I presume I can't ask them to just inspect a small section of the floor area!

My customer's lawyer said that an expert opinion is an expert opinion, even if not from the Tile Association, so make of that what you will!
Agreed, it's expensive and I have my doubts about being able to reclaim those costs on a win.

 

[Flintstone]

All those tiles will pop up with a claw hammer and a light pull

 

[acaciaguy]

I agree sadly. Use this to your advantage

 

[J Sid]

take lots of photos, keep written records of everything, correspond by email.
I'd ask them for the fixing method they use, materials used, substrate material. If they are not forthcoming with this it will go in your favor if it goes to court.
the fixing method does not meet those set out in the British Standards for tiling, as you have pointed out not back buttered, not solid bed, there may well be others.