Floorboard Rot and Neighbor negligence?

Bendy_House

Thanks. So these joists will likely be sitting in the party wall, possibly with next door's adjacent to them.

The external stack was removed before you moved in, and the roof presumably closed over it. Then you had the internal - loft - part removed too?

The party wall goes right up into the loft, but does it also go through the roof? Is it a parapet wall above the outer roof covering? Was this a shared chimney stack? Have the neighbs also had theirs removed?

Basically, is there any way a leak on the roof could be finding its way down to ground level via the old stack, and causing this damp patch?

I'd agree you are best acting along with the other house owner with one surveyor/builder who can examine both sides at the same time and arrive at the source of moisture. If there really aren't any leaking pipes there, then it must surely either be from below - ie either 'rising' or due to condensation from a lack of ventilation - or from above, if there remains a path from the roof?

Could you take a couple of outside photos of the roof to show where the stack used to be? One of your side of this parapet, and one from t'other?

stuart45

How old is the property? The sleeper wall would normally have a DPC and then a timber plate on top. 
The fender wall may still in there where the hearth was, it could also be full of hardcore. Should be removed when the floor was boarded over after the removal. These photos might give you a better idea.