Bathroom walls - what are they made of?

[Beginnersluck99]

Hi, I'm rennovating my bathroom and stipped off the wallpaper to reveal a pink boarding material. From where the previous owners have drilled holes to attach shelves etc the boards appear to be made of wood. At first, before I stripped the wallpaper off I thought this was chipboard but now it appears to have a pink coating on the surface of the wall boards. I can't tell what it is made of, maybe some waterproof material? I've searched online but can't seem to find what this might be. If anyone has any ideas and if they know if it is waterproof and can I paint directly on it, I'd be very grateful. Also, can I tile directly onto it?
Thank you!

 

[s60tsy]

i had something sounding like this in my bathroom when i started rennovating it, it was like a really thick wallpaper that seemed waterproof, getting it off for the plasterer though was an absolute nightmare it was backed or sealed on with a tar substance and took hours to fully remove. I had the same tar in a room downstairs which i left bits on before plastering and they seep dark stains through the plaster and paint. yours may be this and may be waterproof apart from the holes you said about? it may be different stuff, my house is an 1890's terrace

 

[Beginnersluck99]

Thanks for the reply but I'm not sure mine is the same. My bathroom is a 1970s extension and the pink boards are attached to the wall like plasterboard would be. They are obviously made of some kind of wood inside but the surface of them is a pink coloured waterproof looking material. Your tar stuff sounds a nightmare though, glad I don't have that I think I'll just try painting my pink boards directly with bathroom paint and hope for the best

 

[Newboy]

It's possible that it's fire rated plasterboard (Gyroc fireline)
The previous owners may have hit studs when mounting shelves etc