Mould growing behind vent

CardiffCrank

Just moved in (FTBs) and discovered this patch of mould in our kitchen. It was behind a piece of furniture and the surveyor didn't catch it. On the outside of the wall, directly in line with this patch, is this vent. It's hard to tell from the photos but the vent looks a bit clogged.

Any advice? I wonder if the vent is not letting air through while also making that patch of wall a bit colder, so that condensation forms there and then doesn't dry off. Does it seem reasonable to get something like a screwdriver out and try to get any crud I can out of the external vent, hit in the inside with some vinegar spray, and then hope for the best?

shiraz99

It'll likely just be a cold patch leading to condensation and mould, particularly when you've got furniture and the like pushed up against the wall. Best think to do is fully clean the area with a bleach solution and/or mould killer, if it's on wallpaper then strip that too and treat the underlying wall. Then leave the area clear to allow air flow.

How old is the property, is it a solid brick wall construction?

CardiffCrank

1950s council semi - brick with cavity wall. This particular location seems to be paint on plasterboard actually. Does that make it more challenging or is it probably just all on top of the paint?

stuart45

Years ago cavity walls often had the cavity vented with high and low level air bricks. However the practice was stopped because of this issue with cold spots. It was also thought to increase the U value to more than that of a solid 9 inch wall.