DIY Doctor UK DIY Forums

Hi
I live in a bungalow and recently noticed some damp in my living room. To cut a long story short I lifted the floor to find rotten joists and mould on underside of flooring. I replaced all of the timbers, treated new ones with dry/wet rot treatment just in case, replaced the floor, unblocked the air bricks (insulation in front of them) and replaced the air bricks around the rest of the house.

Having returned from being away for 2 weeks I lifted a piece of flooring (an inspection hatch I planned for) and the underside of the floor was wet with white mould growing on it. The new joists are also soaking wet with condensation forming on the underside of the new chipboard floor.

This is really getting me down, I thought I had cured it by sorting out the air bricks. The cavity wall insulation also feels wet. Any ideas please? Could it be caused by a wet external wall soaking through to the insulation which is causing it to spread further. I seem to have a lot of condensation on the windows in the lounge even though it is un occupied at present with no heating floor coverings in place.

Any help would be greatly appreciated as I can't re-decorate until this is sorted and it is starting to get me down
Kind Regards
Dean

how much gap is under the floor,it should be at least 150mm.
If the floor under the joists is earth,thats where the problem lies.It should be concrete clear and clean from all obstructions to allow maximum airflow .

Hi Welsh Brickie
thanks for your reply. I've got plenty of clearance beneath and it's concrete which I swept clean when I replaced joists. Since posting this I put a dehumidifier on under the floor which dried it out in about 3 hours and seemed to stay dryish for another 2 days. Having gone back to it today I have moisture and mould on my inspection hatch and I can see condensation on the end beams in the cavity. I made sure I left plenty of room behind joists so I wasn't bridging the cavity.
I do have a drain pipe which is at the corner of the houses but surely if there was a problem with the drain it would soak down and not come back up past the damp proof course??

Any ideas?
Thanks

[quote="Deano5"]Hi Welsh Brickie
thanks for your reply. I've got plenty of clearance beneath and it's concrete which I swept clean when I replaced joists. Since posting this I put a dehumidifier on under the floor which dried it out in about 3 hours and seemed to stay dryish for another 2 days. Having gone back to it today I have moisture and mould on my inspection hatch and I can see condensation on the end beams in the cavity. I made sure I left plenty of room behind joists so I wasn't bridging the cavity.
I do have a drain pipe which is at the corner of the houses but surely if there was a problem with the drain it would soak down and not come back up past the damp proof course??

Any ideas?
Thanks[/quote]
there should be no moisture, obviously the airbricks are not doing the job
I would replace them with bigger ones and add more,I cant think of what else it could be???

where the condensation coming from? the room above or somewhere else?

more airbricks would help remove the condensation and would be a good start, but think about where water is entering the void from?

leaking drains, rainwater pipes, or mains water pipes?

is the concrete floor lower than the exterior ground level? maybe its surface water entering somewhere.

is it rising damp coming up through the ground/ concrete floor?

maybe bitumen seal the void space - floors and walls

Hi both
thanks for advice. I've bought some bigger air bricks to improve air circulation. It's not obvious where water is getting in. There is no water pipes internally in the lounge area as I removed them last year when I got a gas fire fitted (removed old radiator). I do have some blown render on the front of the property so maybe rain is getting behind that and soaking through to the cavity??

I've painted all of the external bricks beneath render with damp seal stuff. May have to remove render to allow wall behind to dry out. May have to check out the drain as well and if all that fails I may move house!!