Dark circles from dot & dab on limestone floor - Tile Advice

[Excalibur]

Hi everyone,

Going through a major refurb on the house and recently had a 13mm limestone floor installed in the kitchen. After a couple of days, dark circles started appearing on the slabs which suggests that the tiler used dot & dab to install (see picture). Not sure what adhesive was used but will find out.

There's a wet underfloor heating system underneath so I'm already aware that using dot & dab reduces the effectiveness of this and generally is an inferior way of installing tiled flooring.

Believing it to be just a moisture issue, we've been using heaters and dehumidifiers to try to dry the stones out over the last few days but nothing seems to have changed. I'm now worried they are permanently stained and need to be ripped up and replaced.

Would welcome any thoughts from some experts on here. Thanks in advance.

 

[Excalibur]

Update:

Adhesive used is Topps Tiles rapid set flexible S1 adhesive in white. The adhesive thickness is c.15mm. The flooring underneath was latexed so was very flat already. Main contractor has said that adhesive was applied to both the floor and the back of the tile, then dot & dab was used between the two.

Some further photos attached

 

[Dave]

Totally wrong installation method used. And why is the adhesive so thick. The circles might dry but I’d be more worried about longevity of that installation

 

[bsc ceramics]

Not good at all, as said wrong way to lay any floor. I think you will have problems
in the future. Hope uv not parted with your cash yet..