Damp proofing a party wall

Treatments that involve the wall

• Injected chemical damp proof courses, drilled into the mortar along the base of the wall
• Physical damp proof courses, where a slot is cut and a membrane inserted
• Electro-osmotic systems, with electrodes set into holes drilled in the wall

Why it matters next door

Drilling along the base of a shared wall can disturb the neighbour's plaster and floor finishes, and a badly installed damp proof course can bridge or divert moisture. A notice lets their surveyor check the method.

Before you treat the wall

Make sure the damp is not caused by something simpler, such as a leaking gutter, raised ground outside or a blocked air brick. Plenty of party wall damp problems need no work to the wall at all.

Costs

If the work amounts to repairing a wall that is defective, the cost can sometimes be shared with your neighbour, depending on how each of you uses the wall and who is to blame for its condition. Otherwise it is yours.