What is lateral damp?
Lateral damp is when groundwater penetrates sideways into a property, and it can affect any floor that is in contact with soil. If untreated, this damp can erode building materials and cause a room to be uninhabitable as the amount of moisture will make electrical plugs dangerous and the space useless for storing products or materials.
Lateral damp causes more problems than just an unpleasant basement, it can also lead to severe structural issues for walls which the entire building is relying on for support. The increase in moisture content in the air can also lead to increased condensation and mould with all the associated health problems they cause.
Though they’re similar and affect the same parts of a building, lateral damp is not to be confused with rising damp, which is caused by water travelling upwards through porous building materials. However, these two types of damp are often linked, and can occur at the same time, so just because one’s been diagnosed and solved doesn’t mean you’re damp-free.
What causes lateral damp?
Buildings on sloped ground are also more vulnerable, as the slow flow of groundwater downhill puts additional pressure on any walls in the way.
But it’s not always underground floors that are affected. Soil also rises over time, exposing groundwater to walls not originally built to withstand lateral damp. In such cases, in addition to treating the damp, it’s worth excavating excess soil build up to stop the problem reoccurring.
Lateral damp can become even more serious if hygroscopic salts from the surrounding soil contaminate the walls. These salts are constantly absorbing moisture, even from the air, which can rapidly accelerate a damp problem as the wall ends up being attacked from two fronts.
You’ve probably seen lateral damp on a small scale when a flower bed is attached to an external wall. This wall will usually have a wet surrounding the flower bed caused by moisture being absorbed from the soil, which is exactly what happens when soil beneath the ground rests against a wall.