Damp in basements and cellars - Causes and solutions
Damp in basements, cellars and below-ground walls is common because these areas are in direct contact with the earth and are subject to the pressure of water in the ground. It can appear on the inside walls of a cellar, on a partly buried façade or in a basement, with marks that vary depending on the type of walls and the surrounding environment.
Common signs include: walls that remain damp to the touch, tide marks at the base or over large areas, whitish deposits (salts/minerals), deteriorating joints, a musty smell, and sometimes localised trickles of water. In cellars, more general damp can also be observed, sometimes accompanied by mould on stored items or in poorly ventilated areas.
This page helps you recognise the typical signs of damp in basements and cellars, and distinguish it from other forms: condensation often marks corners and cold surfaces, while water infiltration leaves localised stains or gets worse after heavy rain. The aim here is to understand the most common situations (below-ground walls, contact with the ground, poorly ventilated areas) and to correctly classify the type of damp observed on these walls.
Rising damp
Rising damp can affect older buildings when the masonry has no effective damp-proof course. Porous materials, such as brick, stone or mortar, then let water rise up from the ground.
The marks generally appear at the base of the walls. Salt deposits and deteriorating coverings may also be observed. A diagnosis makes it possible to distinguish this cause from water infiltration and condensation.
The causes of damp in basements
Damp in a basement can have several origins: lateral infiltration through below-ground walls, rising damp or condensation due to insufficient ventilation.
The most common signs are:
- Damp marks or whitish deposits on the walls;
- A musty smell;
- Deteriorating paint or plaster;
- Mould on surfaces or stored items.
Noting where the marks are and how they change after rain helps to guide the diagnosis.
Preventing damp in a cellar
A damp cellar requires action suited to the cause of the damp. A below-ground wall can let water from the surrounding soil seep in; a cold surface can also be affected by condensation.
Before starting any work:
- Check the ventilation and air circulation;
- Look for leaks and points where water gets in;
- Have the waterproofing of below-ground walls checked if necessary.
We recommend treating the source of the damp before redoing any coverings. Our ATE and ATG devices are designed for rising damp; they do not replace a waterproofing repair.
Damp marks on façades
Damp marks on a façade can be caused by water entering through a crack, a damaged joint or a faulty gutter, or by rising damp at the base of the wall.
Signs to watch out for include:
- Persistent stains or streaks;
- Blistering paint;
- Render coming away;
- Salt deposits on the surface.
The origin of the problem must be identified before choosing a treatment. Depending on the diagnosis, repairs to the joints, the roof or the waterproofing may be necessary. A crack also needs to be checked appropriately.
Choosing the right solution
To treat damp in a cellar, basement or façade, start by identifying its origin. Ventilation, repairing a leak and waterproofing work address different causes.
If the diagnosis confirms rising damp, we can tell you about our ATE electromagnetic devices and our ATG geomagnetic devices. The choice depends on the area to be treated and the layout of the building.
