Wall/ceiling stain - but no obvious cause, weird !

Dick_here

Hi all


We've got a dark, damp looking stain (not mouldy) that is on the wall/ceiling above the stairs so not reachable from below. It doesn't look wet on the wallpaper though. It is in line with the chimney breast. We've had roofers and plumbers round and they all can't see anything that is causing it, no roofing or plumbing leak they insist. I've looked in the loft too - regularly - and nothing is wet there.


It can't be a 'real' leak or else we'd have dripping water I assume. It seems that it dries out overnight as the stain doesn't look as dark when I get up, but during the day gets darker again.


Damp/condensation would go mouldy I assume ?


I'm at a real loss, so any ideas welcomed !!!


Thanks guys.

Aylesbury_Duck

Could it be a cold spot where water condenses? Is it noticeably darker on cold days or in the morning if you've had your heating off overnight?

Dick_here

Aylesbury_Duck wrote: »

Could it be a cold spot where water condenses? Is it noticeably darker on cold days or in the morning if you've had your heating off overnight?

Thanks. I'd guess the brick chimney breast could be a cold spot. It is darker during the day, it is lighter in the mornings (the heating is always off overnight).

Aylesbury_Duck

Do you generate lots of moisture by drying washing indoors, showers without extraction, lots of cooking, etc? If it is a cold spot and it's noticeably worse during the day, it would correspond to increased humidity levels, although I would expect it to be worse overnight as the general temperature cools and the air can't hold its moisture.

I think you need to get up there somehow and see if it's wet to touch. Or perhaps put some tissue on the end of a pole, hold it up against the stain and see if the tissue absorbs moisture.

Dick_here

Aylesbury_Duck wrote: »

Do you generate lots of moisture by drying washing indoors, showers without extraction, lots of cooking, etc? If it is a cold spot and it's noticeably worse during the day, it would correspond to increased humidity levels, although I would expect it to be worse overnight as the general temperature cools and the air can't hold its moisture.

I think you need to get up there somehow and see if it's wet to touch. Or perhaps put some tissue on the end of a pole, hold it up against the stain and see if the tissue absorbs moisture.

Humidity from showers etc, yes we have that situation.


Good point, what would it help prove though by touching it though (excuse my ignorance) ? If it was damp to touch it sounds worse, but if it is dry to touch - though dark - we've still got a mystery of a problem, correct ? Or is there a more likely explanation either way based on that ?

Aylesbury_Duck

I think you need to establish if it is indeed damp. It sounds likely, but the tissue test would confirm it. If it is damp, and previous investigation suggests that there's no obvious source of water, that would suggest that condensation is the problem and that a cold spot is providing the opportunity for vapour to condense. If that's the case, you need to do two things. One, reduce the amount of vapour in the house. There are loads of threads about that on here, but fitting proper extraction in bathrooms and kitchens is important. Drying clothes inside should be avoided or done in well ventilated areas. Leave trickle vents open or a window slightly ajar. Consider buying a dehumidifier.
Two, you should consider what can be done to remove the cold spot. From your description I'm not sure how accessible it is, but is there sufficient insulation in that part of the loft? Is there something providing a contact bridge so that that part of the ceiling is in contact with something cold like a metal beam or pipe?

Dick_here

Thanks again. And if it isn't damp ? What does that say ? (I'm at work now so can't touch it right now !)

FreeBear

Is the flue within the chimney breast in use ?
How old is the property ?

If it is an old property and the flue is disused, it could be damp forming inside the chimney (especially if it isn't capped & ventilated) and tar deposits are migrating through the brickwork.

Short term fix would be to slap some stain blocking paint over the affected area and redecorate.

Aylesbury_Duck

!!!!_here wrote: »

Thanks again. And if it isn't damp ? What does that say ? (I'm at work now so can't touch it right now !)

I don't know. FreeBear has posted a plausible reason behind it, but all you can do is establish if it's wet, when it's wet and then try and eliminate possible causes. If FreeBear is correct, it may not ever feel damp because the dampness is inside the chimney and the stain is the external (to the chimney) manifestation of the problem in the chimney.

If it doesn't feel damp, to get to the bottom of it and check FreeBear's theory, you'd need to get inside the chimney and see what's going on. Screwfix and other places sell endoscope cameras with LED lights on them at around £30 that are ideal for that sort of thing.

Hopefully it's a cold spot where condensation is collecting. If it's damp in the chimney, the chimney will need ventilating and capping.

Dick_here

Thanks guys, all advice greatly appreciated !

beautiful_ravens

Sounds like tar getting through from the chimney.
Sometimes can be solved by re-lining the chimney [I was told]
Otherwise use a stain block or damp seal paint, or that fancy foil wallpaper to cover it over.