We have just moved out of our old terraced cottage built c.1790, and we’re getting it ready to rent out, as we have rented another house for a while.

With all the furniture out we’re obviously spotting issues, one of which is an area of damp in the living room. It manifests itself as darker patches, no mould, no tide marks, just damp patches that extend from about 3ft up the wall and as high as 6ft up the wall.

I’d always put it down to condensation, as it’s in a corner and not well ventilated. When we lived there I always kept it ventilated and heated as best we could. I’d hoped with us out, and not using the shower/cooking/washing that it would disappear, after a week of it being vacant it’s worse though.

I’ve now noticed that it seems to get worse after wet weather, which would indicate penetrating damp, but the same wall upstairs is dry as a bone, as is the ceiling, as is the loft.

There is evidence of a chemical DPF having been installed before I bought the property, and I also have a pretty useless guarantee passed to me from the previous owners, that requires me to have the original receipt for the work to be valid, which I don’t.

What would be the best course of action? I obviously want to rent it out, but it’s going to put people off.

Wondering if I should try a dehumidifier for a week or so to see if it is condensation or call in a specialist approved surveyor, re-plaster in lime or something else.

Any experience/advice gratefully received.

What’s on the other side of the wall?

Is it near a chimney?

My last house we had a damp patch on the same wall as the chimney and it was rain falling down the chimney and penetrating the wall from within.

What’s on the other side of the wall?

Sorry, I should have mentioned, I have been into the neighbours house, and there’s nothing on the other side of the wall, and no obvious sign of damp on that side, although it’s papered with woodchip and years of emulsion on top.

water can track all over the place. we had to have our chimney completely re-rendered and leaded last year.

it was suprising how far away from the point of entry the water damage was.

Damp is not near a chimney. Unfortunately, all the possible obvious and easy to sort causes don’t seem to be the culprit.

Anyone got experience of using a specialist surveyor?

water can track all over the place. we had to have our chimney completely re-rendered and leaded last year.

Still wondering if it could be penetrating damp

If it starts 3ft up the wall & extends above that, you can discount rising damp due to a faulty dpc. There must be a leak from somewhere- central heating pipe work?

Damp is a natural feature of many older houses. The problem is that the ‘modern’ approach to damp-proofing – chemical treatments/sealed windows/doors etc – when applied to an older house with no membrane tend to trap the damp rather than do what it should be doing naturally, which is escaping into a well-ventilated house. Modern households are worse ventilated, warmer, and produce a lot more moisture that adds to the problem.

When you vacated the house you closed all the windows and doors, air stopped circulating and the damp worsened.

Yes, agreed. Hence why I wondered if I should re-plaster with lime to aid the breathing?

I need to ventilate it while I’m not there, but keep it secure at the same time.

Tape clear plastic sheeting across the wall, if its wet behind its coming from the wall, if its damp on the surface its condensation.

It could be ‘rising’ damp if the wall treatment didn’t work…especially if the neighbour has had their side treated with waterproof plaster and your side was re-plastered up to about 3′ from the floor which I believe is common with these scam happy damp firms.

your side was re-plastered up to about 3′ from the floor which I believe is common with these scam happy damp firms.

The 3 foot bit made me think exactly that.

Given your security concerns, positive pressure ventilation might be a lot less faff than replastering, which TBH will just let it out to condense somewhere else (if it is coming out of the wall, that is).

Whether it would be as effective WRT damp entering a downstairs room, I don’t know.

I’ve now noticed that it seems to get worse after wet weather, which would indicate penetrating damp, but the same wall upstairs is dry as a bone, as is the ceiling, as is the loft.

Which would indicate water coming in.

I’d start by looking on the roof, then the gutters etc and finally the walls (including at ground level).