Damp & mouldy wall - solid wall

Hello,

We've got a fairly nasty damp problem in our bungalow with black mould growing on the wall.

The exterior walls are solid with no cavity (bricks are placed lengthways and then to tie to second skin at every other course - for example they look like this: ___ _ ___ if that makes sense!)

The DPC looks ok and is bitumen - bungalow was built in 1957. Surrounding one of the damp walls is a concrete path right up against the wall, about 150mm below the DPC, the other has bushes, and one has nothing near it/is clear. The internal floor has subsided (dropped by 10-20mm as an entire slab) and has come away from the skirting so you can see the DPC in the wall. I suspect a broken drain at the front but that has been diverted so no reason why the wall is still getting damp.

Any ideas what might be causing it? The walls seem to condense when cold out and warm inside.

We're doing some fairly significant renovations in the new year and hope to insulate the walls externally then render. The floor gets a little damp as well so was planning on putting a new damp membrane across the floor and up the walls to seal them and also injecting a new DPC around the house in case it was the DPC that had failed, then thin studding with foil insulation inside before plasterboarding. We the plan to lay rigid board insulation on the existing concrete floor and put underfloor heating in a screed on top.
Would this be ok or would this cause more problems than it would solve?

Hi,

I am not an expert but it sounds like what you are doing is a good idea. Insulating externally will help with the condensation. Might also be worth looking at the ventilation?

I would perhaps investigate the drains - if these get damaged they can cause major problems - subsidence and all sorts.

Getting a new damp membrane sounds like a good idea also.

Thanks gissle.

I have thought about temporary ventilation but the wife isn't keen as we have no heating in the bungalow and it easily gets down to 10 degrees in the habited rooms over night - she doesn't want anything else making it colder. This morning was very wet - around -4 outside last night and not that hot in here, but every window was soaked even in unheated closed rooms, and the walls were wet as well in places. Otherwise, all the doors are open and some rooms have ventilation and there is just so much condensation.

In the future, most of the bungalow will get encompassed by new extensions so it is only a large hallway, downstairs WC and snug which will be in the old part of the house with the solid walls. I am hoping that with enough damp proofing and insulating this part of the house won't suffer from condensation anymore.

As for the drains, these will all be replaced as they're full of roots and we'll do that early next year. I imagine they've been like that for years given the state of the place so I imagine they've done what damage they're going to do, and I have put in place temporary diversions to stop them leaking near the foundations.