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Old Mod
Well to be honest, can you trust his judgement?
And “doesn’t seem to think” is exactly the definitive answer you require.
I’ve recently laid over 100m2 of 120 x 120 x 6mm thin tile on to a liquid cement based screed, and all the information supplied stated laitance free, and does not need sanding.
Un-sanded.
The darker patches are surface laitance, you can not adhere to this, it will separate at some point.
You mentioned a thin skin on the bottom of the adhesive!!
This does not mean it no longer needs sanding, for peace of mind I’d still want it done.
A 60# grit copper disc on a floor polisher type machine should work easily enough.
Sanded.
If you expand the image you can see the aggregates in the screed, that’s what we prefer to see before sticking even a mat to it.
When I say we, I mean the crew I personally work with.
Priming is an exact process too.
If it’s applied in coats that are too strong, it can form a skin instead of soaking in to thescreed.
Then you’re sticking to the skin and not the floor.
First coat should be very weak, 5/6-1 with water.
Second, slightly stronger.
If it’s still drying instantly, it could have another coat.
But it must soak in and not pool on the surface.
But your tiler should know this.
I would also insist on a 1mm antifracture mat on top of the screed too, before it was tiled.
As far as the product suggested above, Bal Flexbone 2easy.
Personally have no experience as yet with it, so I can’t comment on its suitability I’m afraid.
But it’s all assumption, very difficult to pin point all the reasons it’s failed without seeing it in the flesh.
