Mould/damp

[Asleeping]

Hi, I looked at a bungalow with a view to buying it.

There is mould in the corner of the living room, photo attached.

There are numerous air vents outside below the damp course. The damp course looks intact, as does the pointing on the brickwork outside.

It looks to me as if the air vent has been added later to try and stop a long term problem. The vendor said that the vent was there twenty years ago when they bought the property.

Has anyone any ideas what could be causing this? I’m concerned that the only way to solve this is to dig down outside.

Many thanks.

[Loofah01]

What else is nearby? Single skin wall? Would there happen to be a leaky gutter above that point? Could easily be a leaky DPC but you'll need some more investigating for that

[PlanDeRaccordement]

I think the vent may be worsening the mould. The cold air coming in it will cause the moisture in the warmer air inside to condense all around the vent and nearby on the wall, and then the mould grows where there is moisture.

Outside it may be a case of the ground sloping towards the house, so rainwater pools against the outside wall. Have you checked to make sure that the ground outside slopes downwards away from house? If it slopes down towards houses you can dig around the wall and replace dirt with a layer of gravel to fix.

It wouldn’t be a roof leak or leak from above because that would cause mould to grow in upper corner of room.

[PigletJohn]

I don't believe that ventilation causes damp or condensation.

if there is no vent on the outside, rain might possibly get in, but it would usually dry out afterwards.

There is quite a severe problem in that corner. If, on the other side of the wall, there is a kitchen or bathroom, or a garden tap, probably a plumbing leak.

If the floor is concrete, water may be climbing up from a wet floor, often, again, a plumbing leak from a buried pipe or broken drain.

A dripping gutter or leaking downpipe on the outside of the wall might also cause it, thouh this is less common in a post-1945 house with cavity walls.

Quite rarely, a roof or plumbing leak can cause water to drip inside the cavity, resulting in a wet patch at the bottom.

Some photos of the outside, all the way from paving to roof, may be informative.

[Asleeping]

Thanks for the replies.

It is an external corner. As far as we can tell, there are no pipes or drainage there - this room is at the back of the property, behind the kitchen. The mains drainage is on the other side of the property.

The guttering looks ok but we haven’t got up to have a look at it. There are no obvious signs of damp externally.

I will get some more photos at the weekend.

[Asleeping]

Meant to add, the ground is level, slopes away slightly from the wall where the vent is.

There is a flower bed on the right hand wall. Mostly just earth and, from memory, lower than the

[Asleeping]

Sorry, posted too soon.

Lower than the damp proof course.

[PigletJohn]

how old is the building?

have you got any pics that show the pattern of the brickwork?

I would look carefully at the angle connector on the guttering at the corner, and the roof tiles.

[Asleeping]

Thanks PigletJohn.

I’d say 70s, possibly late 60s.

The brick work looks fairly standard but I will take some photos at the weekend.

[PigletJohn]

then it more than likely has cavity walls.

It is unusual for damp to reach the inner leaf above the DPC, although the cavity may be clogged with mortar and builders rubble. On a corner, this is fairly easy to rake out. Removing a brick may also give clues on the source of water. The wall is wetter than I'd expect from a bit of plaster or rubble bridging the dpc, and more than I'd expect from rainwater penetration through a defect. I still suspect some kind of leak.

[Asleeping]

Thanks again.

The guy I got in to give me a quote on some other stuff felt the wall and said he was surprised it felt so wet.

Pretty sure there’s no underground water there. Need to get up a bit higher at the weekend!