Unexplained damp

[Halle71]

We’ve got an unexplained patch of damp at the top of our main stairs.
It’s on the wall to the right of the stairs (opposite side to banister) about 30cm x 30cm and lines up with the third step down at a height of 10cm above the first floor level (see pic).

It is a terraced house and we assumed it was from next door – it is not a mirror image of ours because the houses are staggered and next door has been converted into flats so their stairs are not next to ours. However a builder working in the top floor flat claims it is not originating from there (although we only have their word) but we have not had access.

Alternatively, from what we can work out without measuring, the ground floor flat has an extractor fan on that wall although it is about a foot lower than the damp patch – do you think this could be possibly cause it? I can’t imagine where the damp from there goes and it seems too much of a coincidence but surely the damp would be at the same level – ie below, not above ground floor ceiling level. We have had access to this flat and I noticed very minor damp on their ceiling that would possibly correspond with our damp and also indicate it came from above.

Any other ideas as we are baffled?

What sort of tradesman would we get out to advise us – would it be a surveyor?

Thanks in advance.

[welsh brickie]

it looks like a leaking pipe in the wall from the picture.If its a cavity wall you can hire a fibre optic camera to see into the wall.

[Halle71]

Thanks for your reply Welshbrickie.
I think all our plumbing goes straight down to the kitchen and up to the loft conversion so if it is a leaky pipe I guess it is next door's.
It definitely lines up with the downstairs flat's bathroom so I presume there will be plumbing between the two flats.
I'm thinking aloud - no way you could confirm this online.

Would it be a damp specialist or surveyor who could diagnose the problem?

[paulbalrow]

Hi

Welshbrickie is right. It is unusual to find a patch specifically like this isolated like it is. Would be a good idea to speak with your neighbours. You can also carefully expose the small area of brickwork by removing the plaster and this will give you a better idea.

[welsh brickie]

you can hire an inspection camera from your local hire centre, and drill the wall,Its minimal damage and with the camera you can show the neighbour whos at fault.