ground floor damp - could it be caused by roof?

[damphouse]

We have no damp on the ceilings or anywhere upstairs.
But we do have small amount of damp inside the base of the chimney and about 2m up on 1 of the ground floor walls. A wall which used to be the back of the house but which is now internal.

Someone once told me it was rising damp, but having looked into rising damp it doesn't start at the floor and is too high up the wall to be rising damp.
It cant be penetrating damp as its not an external wall.
Could it be caused by faulty roof even though there is no sign of damp upstairs or on ceilings?

I've no idea but you have described my situation exactly.
I wondered if ours was due to something being stuck inside the chimney (?birdnest) and that holding on to damp when it rains.
My other thought was that whatever has caused the damp has now gone but the salts are left in the old plaster and attract moisture from the air when it rains or I'm cooking spag bol!
Hopefully, someone will come along and tell us both.