Quick answer. A party wall is the wall that separates your building from the one next door. When it is exposed, because the neighbouring plot is empty or the building next door is lower, it takes rain and sun directly, and it was often never properly protected. The solution is usually to repair the cracks and protect it with a waterproof, breathable coating.
Would you like us to take a look? Send us photos and we’ll give you a no-obligation quote.
Why party walls cause problems
- They were built on the assumption that another building would cover them.
- They often have a poor finish or no coating at all.
- They take wind-driven rain over their full height.
- The joint with the neighbouring building is left open.
How to tell if the damp comes from the party wall
- The stains appear on the wall facing the exposed side.
- They get worse after rain with wind from that side.
- From outside you can see cracks, unprotected brick or loose render.
- If the stain appears mainly in winter, in corners and behind furniture, it may be condensation. We explain it in damp from the facade or condensation.
Common solutions
- Removal of loose areas and crack repair.
- Sealing the joint with the neighbouring building and the top copings. See joint sealing.
- Waterproof, breathable coating that keeps out rain without trapping moisture inside the wall.
- Finishing paint, if the system needs it.
On tall party walls, rope access lets us work without putting up scaffolding on the plot or on the neighbour's roof.
The neighbouring building and permits
Sometimes access is needed through the roof or plot of the building next door. It is best to discuss it beforehand with the neighbours or their property manager. If the public highway is occupied, the town council may require a permit. If there is any doubt about who owns the wall and who should pay, check with the property manager.
Common mistakes to avoid
- Painting without repairing the cracks.
- Using a coating that does not let the wall breathe.
- Treating the damp from inside without stopping the water getting in from outside.
- Forgetting the top coping of the party wall, where water also gets in.
Common questions
Can the damp be fixed from inside the home?
The appearance can be improved, but if the water comes in from outside, the stain comes back. The outside face has to be protected.
Is scaffolding needed?
Not always. Many party walls can be repaired with ropes from the roof, especially if they are tall or the plot below is not accessible. We compare the options in ropes or scaffolding: how to choose.
How long does the repair last?
It depends on the system and the exposure. A suitable coating, properly applied on a sound substrate, protects for many years if it is checked regularly.
Do you have damp in a party wall?
Send us photos of the wall from outside and inside and we will tell you what we see.
Or write to us at info@buildararat.com
This guide is for guidance only and does not replace an inspection of the property or reports by qualified technicians.