Mould on lining paper but not plaster?

[MICH43L]

Hi all,

We had small room with two external walls and a pitched roof that was leaking. A couple of years ago, I got the leaks sorted out (I think) and the exterior repointed.
My mistake, but at the time I decided that wet plastering was the best way to go, and spent far too long building it all back up from brick. First attempt at wet plastering, and the finish wasn't great. We covered it in thick lining paper and painted - it was good enough for a spare room.
So two or three years on, and there's massive mould patches spreading on the external walls. I have started stripping the paper with a view to knocking all the plaster off and treating the brick before boarding out. Expected to see the mould coming through the plaster but it's lovely and pink.
What's going on?

 

[Jadele]

Its likely mould growing due to surface condensation rather than damp penetrating the brickwork. A spare room will often be less heated and all the moisture laden air will dump that moisture on the nice cool external walls especially behind wardrobes etc where there is little air movement.

 

[MICH43L]

You're dead right about the wardrobe issue. Shocking behind there. I've emptied the room, I think I will remove all paper and paint anti fungal on the plaster, leave it a bit and repaper, just ensure enough ventilation and maybe one of those little moisture traps in addition to the dehumidifier we have on the landing below.

 

[Jadele]

Assuming it is just condensation you could dot and dab them two walls with insulated plaster board. skim and paint and that should solve the issue without the need for running a dehumidifier. Obviously if there is a roof problem then you would just be hiding a problem.

 

[MICH43L]

More recently I've been doing batten / board with insulation between the battens for external walls, and ideally I'd knock the old plaster off and do that. But I have an attic and three bathrooms to renovate, so don't really have the time at the moment.

 

[MICH43L]

Mm.. Insulated lining paper.. A medium term fix.

 

[foxhole]

insulated lining paper fixes nothing, ventilation prevents condensation.

 

[MICH43L]

It will help reduce the cold surfaces. A few other changes should also help, eg taking out much of the furniture (its going to be an office), looking at better dehumidification and/or cracking open the window a bit where possible.

 

[DIY67]

Well I lined all the upstairs external walls on a Victorian semi with no cavity wall. So far it has been great on all walls that used to attract condensation. However, the outside wall on the inside of a wardrobe cupboard is now damp to the touch with black mold patches starting. It has been dry for weeks since I hung it (4mm thermal backed lining paper with Wallrock thermal paste) but I am pretty shocked it has attracted condensation given the wall has been warmed with the paste and foam backing. Why would it still attract moisture as the walls are sound outside.