Problem: Rising Damp

Rising damp occurs where moisture is absorbed from the ground into a wall or floor. Think of how spilt liquid on your worktop soaks upwards into a sponge – that is exactly how rising damp happens in a wall, only much more slowly. This is called capillary action.

The first thing to understand is that the bricks, stone and mortar that make up our homes are all absorbent to some extent and as they age, they tend to absorb moisture more readily. For this reason builders install an impervious plastic or polyethylene barrier strip all round a new house, just above the foundations. This is called the "damp proof course", commonly known as the "DPC" and it stops ground moisture from absorbing up the walls. Older properties were often not fitted with any DPC or it may have failed over time, as the bitumen, tar and slate used before the advent of modern plastics were often not very durable.

Checklist for rising damp*:

1. Damp or mouldy skirting boards.
2. Plaster is damp to a maximum of one metre above floor.
3. White marks appear on the plaster (groundwater salt contamination).
4. Paint is bubbling due to salt contamination (up to one metre).
5. Wall paper is peeling due to moisture and salt contamination (up to one metre).
6. A "tide" line is visible and doesn't dry out, even during summer.