Is there a right and wrong way - Fixing floor tiles

[Total]

I have a question about different methods of setting (fixing) tiles to flooring.

All manufactures of tile adhesives/glues state that concrete or sand/cement screeds should be allowed to cure for a certain amount of time before the application of tiles.

I understand this.

What I don't understand is how floors tiled with porcelain tiles, which have such a low absorption rate, can be fixed with cement dust to a wet bedding of sand/cement? I am under the theory that cements rely on both the surfaces - tile and bed - to draw the moisture from the cement to create the bond.

Isn't this method - (thick-bedding) - a contradiction to what the adhesive manufactures believe, that the bedding has to be dry. I know that Im comparing gluing a floor to thick-bedding it but it comes back to the fact that the bedding is wet. And the floors done in this method have lasted and are as strong today as they were all those years back.

I did a job years back that I screeded a bed of sand/cement and then applied mapei cement based glue to the back of the tile and then tapped them in with a mallot. Their still there and their solid. The job was for the local butcher's shop entrance and it gets a good workout 6 days out of the week.

I await your knowlagable responses.

Jeremy

[grumpygrouter]

Cement based adhesives cure by chemical reaction not by drawing moisture out of the mix. If moisture is drawn out it can increase the speed of reaction slightly or even in a worst case, draw it out too quick and not allow the curing process to happen correctly.

Dispesion adhesive on the other hand (tubbed stuff) does rely on moisture evaporation to cure properly which is why it is not usually recommended for porcelain or large format tiles.

[lucius]

Hi Total we lay crazy paving drives in various stone with the method you describe, it never moves.
Lucius.

[oogabooga]

I've wondered how well a porcelain tile might stick when a cement slurry or dusting method is used - I know it works fine with ceramic. Never done it that way with porcelain because I'm afraid it wouldn't bond. Might do a sample board and see what happens.

[garythetiler]

when i do this method i put sbr in my slurry when fixing porcelain

[Total]

Porcelain tiles will stick when laid onto sand/cement bedding with the cement dust, but it is better to coat the back of the tile. Not fun when replacing tiles on old floors when laid this way.

[whitebeam]

As Gary says, sbr is the dogs danglies