Case study
Petersham: When Every Wall Is Covered Up
The Property
An older brick house in Petersham with an original front section and a newer rear extension. Every wall in the original house had been covered with plasterboard or timber panelling. The floor had been raised 45 to 50mm over the original, and the front room floor was sinking.
With no wall visible, the evidence had to come from everything around them.
Reading a Covered House
Someone had cut vents into the walls themselves. The front room floor was dropping because bearers and joists were rotting where they touched wet masonry. Outside, a subfloor vent sat below the level of the external concrete, so water was running under the house, and there was mould on the wall.
Covered walls on their own can mean anything. But covered walls plus owner-installed wall vents plus a raised floor plus a sinking, rotting front room all point the same way.
What was causing it
Rising damp in the original house, hidden behind the linings. Covering a damp wall also stops it drying at the surface, so the salt damage usually climbs higher behind the sheeting than it would on a bare wall. I expected to find exactly that once the linings came off. The newer rear extension was left out of the injection scope, with the junction between old and new to be checked on site.
Options I quoted:
- Injection to the original house only
- Injection plus removal of plasterboard and panelling
- Render removal to about 1.2m throughout
- Re-render with a 3:1 salt resistant mix
- New cornices where full-height sheeting comes off
The lesson
Covering rising damp does not fix it. It hides it and pushes the damage higher. If you are buying a house with every wall lined, get it checked first with a pre-purchase inspection.