Floorboards Damp or not?

[darkpeak]

We have recently moved in to a 1920's terrace, there are 3 small damp looking patches on the floorboards in the downstairs rooms. when you touch them residue is left on your fingers. So I though may be rot or damp.

I took a floorboard up to have a look underneath and the underneath surface of the floorboards are dry with no residue. There is no leaking pipes, and the under floor cavity is not bone dry but I would not really call it that damp either.

I tried cleaning a patch it sort of took the residue surface off but a couple of weeks later it was back as it was.

The patches are not changing size in anyway (smaller or bigger)

I have had 3 general builders opinions on it -
1)could be a bit of damp
2)could be some split oil type product
3)no idea

so any ideas what it could be and how to sort it if needs be?

 

[markie]

If it's not getting worse and there's no water of any sort, why don't you peplace with new boards, and if they get wet stop spilling your tea/drinks on the carpet,

 

[JohnD]

Put your cat, dog and small child outside for a few days.

 

[darkpeak]

we did initailly think it could be Mouse pee - but the patchs are to big - unless the mouse is a real drinker!

If I can avoid don't really want to replace the boards but it is looking like the only option.