:? I have discovered a brown fungus growing behind tiled wall in bathroom. I have removed the tiles.......very damp behind, plasterboard very wet and just crumbled as tiles came off. I have taken all of the tiles and plasterboard off... battons holding plasterboard v wet and rotten so I have removed these also. What should i treat the walls with? should I line it with damp proof sheeting then replace battons on top of this ready for new plaster board or should I paint the walls with a water repellant paint and do I need to treat the walls with an anti-fungal agent even though I have cleaned the walls?????? thankyou and I look forward to hearing from you.