We discovered a crack in our shower tray, which subsequently got so bad we had to remove the tray (we don't use the shower so this didn't matter). On removal we found a large round headed rivet, protruding from the floor, which had been there since comstruction. It wasn't countersunk, so the tray was always going to have a weak point. OH filed it off slightly, covered the floor and part of the walls with waterproof cushioning, then fitted bathroom quality vinyl flooring. It looks lovely, isn't cold or ridged to walk on, and is far better than what we had before.