Drying out a damp house - experience?

[PastaFasool]

Anyone had experience drying out a very damp house after it's been unoccupied?

Bought a 1930s terraced house before the summer that had been largely unlived in for the past couple of years. Windows had been painted shut, curtains and blinds closed for months.

We had specialist damp surveys done, who recommended letting the house dry out once the windows were replaced before doing any damp treatments.

We've been in the house for 3 months now. Replaced all windows, been getting lots of fresh air into the house, heating on when needed. However, we're getting a lot of cracking paint, peeling lining paper... our survey found no evidence of subsidence but did warn we'd probably get shrinkage on plaster and lath walls.

Anyone had experience of what more to expect?

We live in a 1930's semi and found the worst of the damp was behind the skirting boards and where the damp had seeped in under the rotten window frames. Can you get a dehumidifier or two of them and leave them running a while too? We had a silverfish infestation in the kitchen due to the damp. Once a house gets cold and damp it takes quite a while for it to dry out. Also check that any air bricks are free of rubbish etc and if you have a chimney even if you don't use it perhaps get it swept and have bird cowls fitted as crows and jackdaws etc will drop twigs down which then get wet and hold the damp. Do not get cavity wall insulation as 1930's houses are not really suitable. Hope you dry out soon.

I wonder what kind of paint is it. It might make the difference.

Do you need air bricks. Has anything else been bricked up or covered when it shouldn't have been? Some houses should have a ventilation type brick under the front bay window, and when these are covered or filled in, it causes issues.

Is it cavity or solid walls?

If paint etc is peeling you might need to strip it all back to original plaster and re-do with properly breathable materials.

Do not let anyone near it with injected 'solutions', damp-proofing, tanking, replacing lime with gypsum.

Heating and ventilation are key, slow and steady for both works best IME.

Dehumidifiers can make it worse if you've got solid walls as they draw moisture out of the walls too quickly.

We had a lot of issues with damp in our 1950s semi. The thing that finally sorted it was replacing the roof felt with a new more breathable one and putting in 2 air vent roof tiles on each side of the roof. And having a dehumidifier running all day long - we got ours from AO for about £250. We put it on from October to April ish.

In our experience of several damp houses, both old and new, it takes around 12 months to dry out after sorting out whatever the causes were first. (Gutters/bridged damp proofing/leaky windows and roofs for us.)

Thanks all for the advice! The house does seem to be drying out, but we do need to also get the front stonework fixed and some gutter repairs done, now that the new windows are in.

Front wall brick covered with stone, back wall is brick cavity. We had a cavity survey done plus the window guys had a look, seems like it needs cleaning in the cavity. Good to know about the insulation - we'd been advised by neighbours that they regretted having it done...

Walls are brick covered with plaster and lath internally I think. Lining paper on all the walls which was OK when we moved in but now starting to unpeel a bit, I think it's because of the temperature and humidity change?

It might be, or might be a sign of moisture trying to escape. See how it is after a couple of seasons of hearing and ventilating.

Thanks @Scampuss we'll get the roof and gutters checked, and front stonework fixed, then give it a couple of seasons.

It's a lovely solid old house but it's definitely in need of maintenance that the previous owners gave up on...

Check that the ground level outside isn't higher than the damp proof course.

Also check below the floorboards and see if you can see the water supply pipe to check it's not leaking. Ours was and it was like a small lake under the house.

@MrsMoastyToasty our damp survey did say something about the height of the damp proof course, I will dig that out. The damp is definitely improving, part of me is wondering though whether to wait with painting and plastering yet or wait for more drying out.

What are you plastering with? If not lime then definitely wait until it’s dry. And yes I’d wait to paint.

We uncovered a wall we knew had been wet, but was sorted and a year later the bricks were still damp. Ours was a leak though so if yours is just condensation it might not be so sodden.

Don't decorate until the damp issue is sorted or you will just end up having to redo it (voice of experience). Fixing the gutters is really important as that might mean they the walls are getting wet every time it rains and as we have had a very wet summer, that could mean that they can't dry out at the moment.