Who is responsible for repairing this chimney breast in a terrace?

[megandraper]

We're getting bad damp in a bedroom. It looks like it's coming from the chimney breast in our neighbour's house. It seems that two flashings need to be replaced, one on the side of the chimney breast that faces our house, and one on the back of the chimney breast.

It will be pretty expensive because scaffolding is required to reach it.

Who should pay for the repair? We will get the benefit of the repair (the damp is only coming through on our side of the wall) but the chimney breast itself is in our neighbour's house.

In my mind it should be split 50/50 but neighbour thinks we should pay for it all.

Does anyone know what is right? Or what's usual?

I assume it is a shared chimney so half is on your property and half is on your neighbour's? Which side is the damaged flashing on? If it's your neighbour's side then they have to pay for it to be repaired, even though the damp is only coming through to your side. There is a legal obligation to not let your house deteriorate if it results in damage to someone else's property. If the damage is to the flashing on your side then you have to pay. If it's both sides then you both pay.