Help - possible causes?

[Paulbobbert]

Hi - whole house has been plaster boarded and skimmed, old 1930s house which previously had wallpaper on (and not changed) since 70s. Checked all the walls with a moisture meter and checked the whole place for damp beforehand, found nothing. Now that walls have been plastered and painted for about a year starting to see issues with damp in two of the bedrooms, primarily around the windows but also in corner of room - both upstairs and no other issues in any of the other rooms or ground floor of the house which have all been treated the same. Windows relatively old and so is guttering and fascia but can’t see anything obvious on outside wall. Outside wall has also been rendered recently so not likely to be that. Cavity wall insulation which has been in since the 90s. Any ideas or things it definitely is/isn’t to help me narrow my plight for a solution? Whole house is newly plumbed with all brand new rads too. Currently thinking it seems like a problem with the windows but the corner of the room is throwing me off (though is only the corners on the window wall so maybe now a red herring…) pics attached, any advice gratefully received!

 

[Monkey Boy]

No trickle vents

 

[malc]

The mould would be condensation. It needs the mould wiped off , windows opened and the heat turned up. When a person breaths out there is a tiny amount of moister which goes to the coldest areas of the room. The whole house need better insulation.
The cavity wall insulation sinks about 15% each year, so I guess that there is nothing left on the first floor.
On refurbs the old insulation is pumped out and replace with polystyrene balls.

 

[Stevieo]

The mould would be condensation. It needs the mould wiped off , windows opened and the heat turned up. When a person breaths out there is a tiny amount of moister which goes to the coldest areas of the room. The whole house need better insu
The cavity wall insulation sinks about 15% each year, so I guess that there is nothing left on the first floor.
On refurbs the old insulation is pumped out and replace with polystyrene balls.

The amount of trouble those polystyrene balls cause is unreal. They bridge the cavity and transmit any external problems right inside.

OP malc is right about a spread like thst in corners on window walls being condensation but dont listen him about how to tackle it. You will spend your whole life fighting a losing battle.


Zinsser mould paint is what you want. Its £80 a tin but it works

 

[themucky1]

Stop wiping your cock in the curtains you dirty little bugger

 

[ChrispyUK]

The amount of trouble those polystyrene balls cause is unreal. They bridge the cavity and transmit any external problems right inside.

OP malc is right about a spread like thst in corners on window walls being condensation but dont listen him about how to tackle it. You will spend your whole life fighting a losing battle.


Zinsser mould paint is what you want. Its £80 a tin but it works

No it doesn’t