Hi,

In my end-of-terrace victorian house, the bathroom is housed in a
brick built extension. It is well built and well “integrated” into the
rest of the building. I can't afford to do the internal reorganisation
of space I would like but I need to refurbish the bathroom.

The walls are ceramic tiled throughout. Currently tiles are “blowing”
off the walls and during the recent cold spells the room is freezing
in the morning with puddles of condensation.

I need to pull some of the tiles off the walls before they fall off.
If am am going to do this I'm thinking of insulating the walls. My
idea is to use Kingspan or Celotex or some “finished” urethane board
that I can tile directly. I only want to tile the area around the bath
and shower. What “finish” can I put on the untiled boards that will be
100%(?) water resistant given the 100% humidity level created by a
shower?

Thanks

Clive