Neighbours Chimney leaking into our attic.

We live in a old semi D. We have no chimney on the left hand side of our house. Our neighbour has. In the attic you can see the brown soot and water leaking down the dividing wall that their chimney is on and the attic smells of smoke. I will ask them to fix this. What is the best solution to fix this. The houses have no chimney flues in them. Finally can my neighbour have this prombem fixed by their insurance.

There may be a problem with the lead flashings around the chimney where it protrudes through the roof tile, this can allow rainwater to bleed through along the chimney breast. These will need to be reset if loose, they could be sealed in place if it is minor using a lead sealant similar to silicon mastic.

Cracks in the brick or blockwork can cause the fumes to escape, especially if it is a flueless chimney. You would need to identify where the smoke and soot are escaping and seal the leak. This could be done by replastering the chimney with sand and cement as this will achieve an airtight seal.

Ideally you would look at inserting a flue liner to the chinmey shaft and sealing it into the fireplace. This is possible to do in some situations and would avoid the future risk of more leaks.

Do not delay, get this seen to!

You are under risk of CARBON MONOXIDE poisoning if the chimney/flue is leaking

it sounds like, it is their chimney but your wall, joint effort between both of you to put in a flue liner. there are loads of companies that do this and it is a painless job