Terry’s Guide to Lateral Damp Treatment

Last Updated 28 August 2018

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?

When soil presses against a wall that is cracked or made from porous materials, groundwater can seep through and saturate the wall. Soil becomes wetter the lower you dig down, so the risk of lateral damp is increased for deep cellars and basements.

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.

How to spot lateral damp

Look out for paint that’s peeling or has a bubbly appearance, or plaster that’s discoloured and/or crumbling. The walls are also likely to be cold and wet to the touch, and if hygroscopic salts are present, then you may see a white, chalky coating as well. Black, sooty mould is a dead giveaway of a damp problem and can be just as easily smelled as spotted.

How to treat lateral damp

First, we perform a thorough investigation of the affected floor using moisture meters and our years of experience in damp problems to find the source of the damp and its severity. If we believe the walls are so damaged that they pose a structural risk, we may need to install supports immediately – but these are extreme cases.

Our standard solution to lateral damp is to tank the walls, which first requires us to strip away any damp plaster or rotten timber until we have nothing but the bare brick or concrete. We then leave the exposed wall to air out until it’s completely bone dry or perform specialist works with wet-friendly renders.

Next, we install a special tanking system which makes the walls permanently watertight. This system is provided by world-class damp proofing experts and suppliers Sovereign, and is backed up by a 30 year guarantee. These works can take up to six weeks on a small size basement.

On completion of works, a manufacturer guarantee will be granted and we’ll provide a quote for any plastering or decoration works that you might require to get the basement or cellar looking good as new.

If you have any questions about lateral damp or want to book a free, no obligation survey and quote, call Environ or request your call back today.

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