Our 1930's semi currently has separate plastic guttering systems, with
each half having their own single downpipe, although our downpipe is
cast iron. We've lived there over 10 years, with our elderly neighbour
living there far, far longer. Neither gutter have been replaced in that
period, but as neither is cast iron, both have been replaced at some point.

Our neighbour approached us to say that she's replacing her guttering.
Apparently she also mentioned something about having a damp problem, but
I'm not certain where it is, or whether the guttering replacement is
meant to resolve this. Apparently there was some discussion about
whether we wanted our side replaced as well - we can't afford this.

Today we've been asked to confirm whether we want the guttering systems
connected. At present they're separate, and doing a quick check around
neighbouring properties, there's a mix of both joined and unjoined. I
suspected originally they were joined, but over the years some have been
separated as one half replace theirs.

When I said I was happy to leave it as is, she was fairly polite, but
pressed the point that (she was advised?) as there would be a gap
(however small), that water could run down and cause damp. She
repeatedly said that she's fine with our decision, but to make it clear
she's warned us of the potential problems. I think she was trying to
make it clear that if things go wrong, its our fault.

My reason for not wanting them joined was mainly that it's not been a
problem for the last 10 years (and likely longer), and that I'd like to
avoid shared systems were possible to prevent potential disputes should
one side leak/overflow etc.

What do people recommend? Should we connect our guttering (assuming
it's possible) or keep separate? Is there a real chance of damp due to
the gap, or is it best to keep as-is?

Thanks

David