Why use flexible adhesive to lay stone tiles?

The adhesive isn t flexable as your thinking. I under stand what your saying. The "flexing" is so minute you can t even see it, feel it or notice it in any way.

And as for your grout , most grouts now are modified to do this also. You don t notice it but its there.

As for sealing the stone, you want to prevent water from getting into the stone, this causes the staining , from dirty water or impurities in the water left behind when water evaporates. Water, water in thin set, waterin coffee etc.

If you have any specific questions click on my avatar and you can e mail me directly. I ll always answer ASAP. Right now I m going out to mow and I ll get back with you. GL

you want flexibility to counter movement caused by temperature fluctuations, even minor ones will crack tiles or grout eventually,especially laid on a concrete floor, a few years ago i was working for builder, on his own house,he had me lay down an "anti fracture membrane"on all the areas where there was going to be tile/marble over concrete, it consisted of a fine mesh (almost like window screen)laid down first, then i rolled this black liquid over it when dry it was like the concrete had a thin layer of rubber on it, the tile guys came and laid the tile right on that using their normal adhesive and grout

Are you sure that you took up Ceramic tile? It sounds more like the Asphalt emulsion adhesive generally called Cutback adhesive. Cutback was generally used to adhere Vinyl and Asbestos tiles. Cutback can have asbestos in it as well, so be cautious. Cutback will generally be a thin layer about 1/16" thick with trowel marks showing lines of adhesive about 1/16" thick and 1/16" apart. It is very dark brown to black in color and will usually remain tacky. There are very few other adhesives that will bond well to cutback, it literally eats them up. All that can be done is to cover it up with new underlayment-grade-plywood. Or you can scrape up the adhesive until there are only traces of it left, and then float over it with a portland cement-based patching compound like Dap's Webcrete 95. Then the regular flooring adhesives can be used over that. As far as ceramic goes, be sure to use a good grade of ceramic mortar over suitable underlayment (like Hardibacker). Ceramic mastic is better in lighter use areas like counters and walls. Its bond generally gets weaker over time where mortar gets stronger. I strongly suggest that you contact a reliable flooring specialty retailer in your area. They have the expertise and answers usually far beyond the box stores.

you would not use flexible adhesive on a stone floor ...the only time you use flexible adhesive ..and grout is when you are tiling on ply with a wood floor beneath that ...we dont use this ..backer board they use in the states in the uk ...and the flexible floor will feel as solid as a normal floor ...the only times a tile adhesive would fail is if the original floor had a loose or defective surface