Weird one

nicholas221078 · 2 Jan 2026

Hi all.
In 1 corner of 1 room which is adjoining to the neighbours, I get mould build up in the corner , it literally starts 1 inch down fron the top.
I have re boarded the ceiling 4 weeks ago and painted, now this.
It did happen hear in the past due to the drain pipe blocking up, the water started splashing and hitting a gap between ours and the neighbours fascias, this was sorted.
I've checked in the loft, pulled all insulation back and it's dry up there on the top , I did manage to squeeze My hand down the brick face in the eves and it felt dry.

What else can it be
Thanks

Wayners · 2 Jan 2026

It's a cold spot so condensation forms on surface.
You can add insulation to the back if you can gain access and run a dehumidifier for a few hours every evening.

Also don't dry washing inside without a dehumidifier and try and find ways to increase ventilation.

Watch the skillbuilder YouTube channel on condensation

nicholas221078 · 4 Jan 2026

Hi, as its a corner wall connecting to the neighbours, I cant get behind it , I'd have to remove the eves , it's upstairs .
Then I d have a fight to get insulation down due to wall ties etc.

Thanks

nicholas221078 · 4 Jan 2026

Also we don't dry clothes up there and have a window 1 myr to the side of it with trickle vents open

Wayners · 4 Jan 2026

It's a cold spot. Moisture floats around and will settle on a cold spots no matter where it is.
Trickle vents help ventilation but I'm of the opinion they do little to stop condensation. Humidity in houses now is off the scale. It travels through walls and ceilings. Often in lofts there is no insulation at some edges. Just gets missed as they can't be bothered to cut a strip and tuck behind a joist that's not tight against wall.
You will often see mould around the edges of rooms because of this. I'd pull some insulation off the existing rolls and shove in the missed edge gaps when I was in lofts

nicholas221078 · 4 Jan 2026

I'll pop up and have a look but I did re lay insulation all along that edge .
I'll see if there's a gap and fill it thanks

aveatry · 4 Jan 2026

I had a friend who had a similar problem with a connected to neighbour wall, turned out next door was a cannabis farm and it was leaking watering system

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