Black Mould on plaster behind wallpaper

rdpro

I'm just having my house renovated, which includes removal of external walls (ouch) and rebuilding an entire new outer skin (brick, block and insulation) - it appears that, at some point, water was getting through the old wall in one corner of the living room, and a nice big crop of black mould developed behind the wallpaper.

Now I'm stripping this all off to have the interior reskimmed, what's the best way to treat this blackened area? Chop out the affected area, or can I treat it with something - I'm assuming the new outer wall will have stopped the damp ingress, as there's no other water source near this corner and the floor is concrete. Total area is about 1 sq metre - it's not on plasterboard, so another assumption is that it was growing on the wallpaper, but stained into the plaster.

TIA

owls

chop it out, to be on the safe side, if your getting a plasterer in, ask him to undertake it and his advice.A bit difficult to tell with out looking first hand

benood

It could have been condensation it commonly occurs in corners - was the original wall single skin?

rdpro

original wall was concrete outer, ash block then a grey concretey plaster(?) with a standard skim over that

madeane

Hi
I had this on a job recently, black mould behind wallpaper due to a bath/shower leaking. I removed the wallpaper and the old plaster down to the brickwork, used bonding plaster (could be boarded, depending on the size of the removed plaster) onto the bricks and then skimmed over using Gypsum multi-finish, customer very pleased! Ensure that the cause of the ingress is sorted before any other work is done. Good luck

benood

Still might be condensation but it's less common on cavity walls