Tiling

[I/HATE/DIY]

I have floorboards in the bathroom that have been sheeted with quarter inch ply, what is the best adhesive to use when laying ceramics as I have had problems in the past with tiles coming loose and cracking underfoot?

[Clanad]

If the plywood is not marine grade or the British equivalent recommended for water intense areas, such as baths, then what you currently have should be covered or better, replaced with subfloor material for baths. Having said that, what your are looking for to use with ceramic tile on floors is a mastic called "thin set" here in the U.S., that comes in tubs. Here, in the U.S., the tubs are either 1 gallon or 5 gallon size depending on the areas needed. It can be purchased ready mixed or in bags to mix with water. It's layed down with a notched trowel. The depth of the notches needs to be equivalent to the thickness of the intended tiles. Lay it on the prepared surface in straight lines. The space between the ridges should be almost clear of the mastic. A rubber mallet comes in handy for tapping the tiles for good compression of the mastic. I suspect the reason you had past problems with cracking and loose tiles had more to do with the subfloorng bending and deforming, which, again, is a good reason to consider the soundness of the surface you are preparing... Good luck!

[dummkopf]

You could also try this site which I've found very useful in the past.
http://www.diynot.com/forums/