MRB Plasterboarding Ensuite Bathroom

Not sure if this should be in the tiling forum. I've removed all the tiles and plasterboard from the walls in a downstairs single storey bathroom and have found that the walls have what looks like mould:




The walls are dry to touch though but there have been problems with the felt roof in the past and I will be re-boarding and fibreglassing the roof. Do I need to treat the walls with mould killer first?

I want to tile the entire walls and floor in the bathroom and also want to add some insulation. Can I dot and dab foil-backed MRB unplastered ready for tiling? Should I attach 2 x 1 to the wall, insulate and then fix the plasterboard on?

fix your roof first.
need bigger area photos to advise you on walls.?show most of whole room.

difficult to advise whats best?
best practice would be nock it back to masonry an start again.
whats on the walls now - plaster or lime render?

treat the mould an do the roof
i dont like battens or dot and dab esp in bathrooms.
all wet walls have to have tile on solid plaster or render.dont use any kind ofplasterboard around baths or showers.
sort out all water, and elec supplies to safe zone, an runs and waste an soilpipes.
install an extractor.

is the outside ground level lower than inside?
is the extn rendered or solid wall?

wall render or plaster should be cut back 50mm min from finished floor.

The walls were plastered and I have taken most of it back to masonry apart from small bit by door. The ground level outside comes up to just below the window as the bathroom is just off the basement. The wall outside is rendered and painted.The mould treatment has cleared up most of the black staining now. So you are saying it needs to be plastered again and then tiles directly to this?

Is there anyway I can improve the insulation at the same time or should just the roof be insulated? I am going to install a warm roof and then grp fibreglass the flat roof.

what youve got is a half basement an that changes everythin.
usuly tankin bubble wrap an pumped drainage channels are fitted in full orhalf cellars .
floors tankins are tied in to wall drainage tankin.
anyhow you get the idea that a proper job is detailed an expensive an not usulyfor DIY.

you could just render all the walls in sand an lime an pour bitumen liquid on the floor an tile over that lot hopin to get as long as possible trouble/damp free out of it?

how do you propose to drain waste an soil pipes?

divert any external water away from the walls - check soundness of any gulleys or drainage.