I have a stone shower tray. It was professionally installed 15 years ago in my victorian house on a suspended timber floor on the first floor. It has developed a hairline crack from one side to another. It came with a lifetime guarantee and I have contacted the manufacturer. They asked me whether the tray had been laid on a bed of cement. I said from memory it hadn't. I am now in dispute with them as they say this invalidates the guarantee. My arguement is that a bed of cement on a suspended floor isn't a lot of good. To allow for waste pipe clearance and a fall over 4 or 5 yards of flooring I seem to remember a wooden frame of 2 by 2 or 3 by 3 was constructed as a cradle and screwed to the floor. Your comments would be gratefully received.