Converted garage ceiling

[thwildfire]

We have a garage that's been converted (without building regs) to a bedroom and during the recent hot weather the wallpaper on the ceiling all fell off to reveal some sort of grey polystyrene. I imagine it has been used for insulation but as it's only around 4mm thick I can't imagine it's much use and I'm worried it's flammable. I also think that if we papered over it, it would all peel off again. Would anyone know what it is exactly and recommend what we do with it?

 

[tell80]

its difficult to say without a pic but



it could be polystyrene tiles or polystyrene rolls.
polystyrene is bad news in a fire because of the toxic smoke it gives off.
its usually safe to remove it and use plasterboard instead.