What is Lateral Damp?
Last Updated 13 September 2018
Lateral damp is when groundwater penetrates sideways into a property through cracks or porous building materials.
It can affect any floor which is in contact with soil, but is most common in basements.
Areas that have high water level – such as Fulham, Putney and Richmond – are more vulnerable to lateral damp.
You can learn more on the causes of lateral damp in our article.
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.
Walls affected by lateral damp 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.
Lateral damp causes mould and property damage
If untreated, lateral damp can ruin paint and plaster, spread mould and cause electrical failures and shocks – none of which you want in a basement you intend to spend time in.
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.
To prevent damage from lateral damp, building regulations require that all new builds with basements and all basement extensions are equipped with tanking systems.
You can learn more about treating lateral damp in our article.
Lateral damp is often misdiagnosed
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.
Rising damp is treated with a damp proof course (DPC), while lateral damp is treated with tanking.
Another source of confusion is condensation, which might be caused by increased moisture from lateral damp, or from poor ventilation and cold surfaces.
However, all these 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.
You should also be careful of cowboy “damp experts” misdiagnosing the source of damp in a basement, often conveniently diagnosing it as a damp problem that’s more expensive to fix.