rising damp, penetrating damp, percolating damp, who else wants to get creative?

[JohnD]

a wee, wee stream of water coming off the sleeper walls

the water company can detect what sort of water it is

e.g. tapwater contains chlorine; drain water contains soap

I think gutter water contains leaf material but it's not my sphere.

If it is a tapwater leak they may have an interest in repairing it. Presumably the water main runs under the pavement

I bet if you keep digging you'll find the source.

 

[bobasd]

what happened on sat 5th oct? did you get any answers?

where is your outside stop-tap for your main water supply?
where does the water line run at the front?
where is the interior stop-tap located?
the same questions ref your RH neighbour?

as previously asked: post a pic of the whole front elevation please?
ladder up to the main roof gutters and clean them out if needed - same with any bay roof gutters and down pipe.
completely drop the main down pipe and clean it out and refix it - eliminate any open ground guttering.
clean out with "rods" & a hose the under pavement drain, and securely fix the main down pipe into the pavement drain .