I have done a lot of work for a pub and hotel chain I would say the last 14 years all there toilets and bathrooms walls and floors get plyed, over the years I have tried to educate them that the way to go now is cement board but do they listen no.Even tell them that theres not much difference in price but the owner listens to the carpenters and sticks to ply the times I have been back and chopped tiles out where the ply has moved on the studs and hair line cracks appear and internal corners opening up,Ive told him time and again it cost him more in the long run it was only in the last couple of years that he agreed to have the showers tanked, it takes a lot to change peoples ways,cannot refuse to do the work as it has kept me going for some time, but always have my say before I start a new job for them ,they all say that I dont stop moaning.