Party wall already faulty

[tracykf]

After undergoing renovations in my mid terrace house, the neighbour on one side has claimed cracks have appeared in the plaster due to the work carried out. The wall in my neighbour's property is so damp the plaster no longer has any key and is not bonding to the wall.

I recently appointed a tradesman to replaster the affected wall and it is claimed further cracks have appeared since then. The decorator has refused to paint said wall as it is so wet the paint won't adhere to the surface.

My neighbour on the other side has not been adversely affected by the work undertaken in my property, my property walls also remain sound as both our properties have been damp coursed.

The neighbour with the damp walls is now seeking recompense for the cracks in the plaster. Am I really liable to pay to get already faulty walls fixed when the plaster lacked so much key it was bound to crumble/crack/fall off sooner or later.

[buildersmate]

Cracks in walls are generally caused by movement. Either because of shifting/undermining in the foundations, or because the wall itself (abive ground) has been subject to considerable mechanical pushing/shoving.
Plaster is keyed onto the underlying wall and has no strength initself so it will crack if the wall underneath cracks.
In my opinion, dampness in the wall is unlikely to cause cracking - but it will create crumbling and eventually whole pieces falling off as the top surface becomes detached from the substrate.
The party wall must presumably be double-skin with a cavity between the two houses - otherwise it doesn't make sense that you have no damp on your side. If the roofs above are continuous, it must also be true that the moisture is coming up his side from the ground - but not on your wall (which has had a damp-proof membrane inserted?).
Are you saying that you paid for replastering of the neighbour's wall on his side as a goodwill measure? - the same wall that is still so damp it can't be painted? Are there any cracks on your side?

[tracykf]

Hi Buildersmate and thank you for replying!

The party wall is indeed double-skinned but no cavity - the two walls butt up to each other but are not bonded as the houses were built long before building regs were invented (circa 1800)!

My side has been damp proofed, my neighbour's side has not.

There are no cracks on my side and there are no cracks on my other neighbour's side where exactly the same work has been carried out on my side of the party wall(replastering, damp coursing, cutting away for an rsj and digging foundations for a pillar for rsj).

Cracks have appeared on the damp neighbour's side since the wall has been replastered by my plasterer, but not where he replastered as he only repaired a small part of the wall where plaster had fallen off from when I had radiators fitted on my side. Cracks are appearing in the old plaster where the rsj was fitted on my side and the painter won't decorate as he says the wall's too damp.

I have to say my plasterer had one hell of a job getting the plaster to stick to the wall and had to replaster a much bigger area than was damaged.

If there is no cracking on my side and there is no cracking on my other neighbour's side, why would there be cracking of plaster on my damp neighbour's side?!

Thanks for your help!

Tracy