Lateral Damp can be described as moisture forcing its way through a wall. (Rising Damp is moisture moving from the ground up through the masonry). The illustrations will help you understand different occurrences of Lateral Damp.

You can expect to find lateral damp if the tanking material - that is, the vertical damp proof course - has deteriorated or if it has been omitted or incorrectly installed. Some sypmtoms of lateral damp are the appearance of salts crystallising on the walls, flaking or blistering paint, and deteriorating plaster.

Some likely locations of Lateral Damp
If there's a problem with the vertical damp course you might find cases of lateral damp:

• where the ground is a lot higher than the damp proof course
• in split-level construction
• in basements
• around plastered plinths

Treating Lateral Damp
Lateral Damp is treated by tanking - that is, installing a new vertical chemical damp proof course - in combination with chemical injection, where necessary, to ensure the prevention of Rising Damp.
After the wall has been sealed by tanking, the plaster or rendered finish is applied.

Showers and Baths
It is not common knowledge that showers and baths must be sealed during construction to prevent lateral damp. Tiled walls are not waterproof, because moisture can penetrate the joints between the tiles. Another weak point is the junction of the shower base and the walls.
What's more, raising the floor of the shower above the original damp proof course can cause a breach

We don't hide damp. We stop it.