On Oct 11, 4:32 pm, wrote:
This isn't exactly a diy question, although it might be in the future.
I have discovered that the chimney breast in the loft area of my house
is totally saturated with water. There's fungus on the bricks and the
mortar can be picked out with bare fingers. At the very least the
stack itself in the loft will have to be rebuilt.

Now to the real question. The damage is a consequence of the next door
neighbour's chimney not having any flashing (the two chimneys are in
one stack) so what can I do? I want to get any repairs paid for by the
neighbour, but how do I go about this? Has anyone had a similar
situation where the neighbour's lack of maintenance to their house has
caused damage to your property? If so can you offer any advice please?

This is more appropriate to uk.legal.moderated than here, but anyway.

IANAL. Your neighbour is only liable if he has been negligent -
usually because he knew that damage was occurring. Also note that if
you sue your neighbour, when (if) you come to sell your house you will
have to disclose this as a dispute with your neighbour - and that will
knock a /significant/ chunk off the value of your house.

If your stack is falling to pieces, then his is probably doing the
same. This is going to be a major piece of work, and you ought to
arrange to fix it together (only one lot of scaffolding for starters).

How long has this been going on?

Fungus doesn't feed on bricks, so if there is any fungus, it must be
feeding on something else - probably somebody's rafters. It may be
dry (as opposed to wet) rot. The good news is that once the source of
moisture is removed, the dry rot will die; the bad news is that it may
have already seriously damaged wood a long way from the dampness.

I think you need to start talking to your neighbour - at the very
least you need to get this fixed ASAP before any further damage
occurs. Do try and get it done by mutual agreement - it will be much
less stressful, and probably cheaper than a successful court case (and
obviously MUCH cheaper than an unsuccessful one).