Veranda floor

[Northumberland veranda]

I'm looking for advice on how best to rectify a problem with the floor in my veranda.

The veranda is fully enclosed and built on a concrete slab. A layer of dry screed was laid on the slab to bring the level up. A liquid self levelling screed was then spread over the dry screed. Interior grade tile adhesive was used to fix 1200x400x20mm exterior grade ceramic tiles. I'll try and attach three pictures showing levelling batons screwed to the concrete slab, the dry screed and then the ceramic tiles.
The problem is that the adhesive has not set under the tiles near the outside edge of the veranda with the result that they are still loose 6 months later. The tiles have not been grouted.

I thought the problem was condensation on the inside of the veranda running down and preventing the adhesive from setting. I've had a dehumidifier running for the last few months. The condensation has ceased but the tiles are still loose.

I was planning to take up the tiles and continue the dehumidification but I'd be grateful for thoughts on how to relay the floor.
David

https://photos.google.com/share....F94TW1n

https://photos.google.com/share....F94TW1n

https://photos.google.com/share....F94TW1n

[Tony McC]

Have you checked with the tile adhesive supplier/manufacturer?

Even with some residual moisture, I'd expect a cement-based adhesive to have cured. When you say it "has not set" just how not set do you mean? Still mushy and runny? Or just soft and not binding?

[Northumberland veranda]

Thanks for the quick reply!
The adhesive is solid at the back of the veranda but liquid at the front such that the tiles move under foot, six months down the line.
The tiles are manufactured by Castelvetro and the manufacturers offer little information on tile adhesives. In retrospect I wonder if it was a mistake to use interior tile adhesive on top of levelling screed? Would it have been better to lay the tiles on a bed of mortar on the original dry screed (ie take up the levelling screed)?
David

[Tony McC]

The substrate shouldn't really matter. I suspect there is a fault with the adhesive itself - it may have perished or been out-of-date.

Have you had any communication with the adhesive manufacturer/supplier?