Last summer, I attached ceramic tiles to my polystyrene pool wall using an adhesive specifically designed for the material. The polystyrene had been exposed to the elements for a while and had become powdery. Over the winter, all the tiles fell off. The plan now is to put them back up with fix. Does anyone have any experience? Do I need to use a mesh first? Primer? Or perhaps sand off the powdery surface on the polystyrene?
It might be that a dusty surface has formed on the styrofoam, and then the glue can't adhere, it's like flour on a dough board—the dough doesn't stick. You should try brushing away the dust and attaching a tile as a test. Primer is probably a good idea, but I don't know which type is needed. The bottom tiles should have a solid base to stand on, so the glue only holds the tiles in place against the styrofoam, they won't tip out, otherwise, they might fall off again.
Might be difficult to make it even with the edge at the top, I see, but you have long clamps, keep them in place and put concrete underneath. Just make sure the concrete is in good contact with the bottom of the tiles, and wait a day before removing the clamps.
I would probably think that it is the wrong type of boards to mount tiles on.
I absolutely believe that fix holds better than glue, but talk to a skilled construction sales person (not Bauhaus or similar), whom you trust, and you'll get something good. I would choose Arden or CCHöganäs.
