Direct or indirect contact between ground or surface water and stone or concrete can cause rising damp. Water is extracted upwards, by the natural absorption and capillary action. This process is continuous. Water moves from the ground into the foundation, and from thereon into the walls.
The amount of rising damp is dependent on several factors: the construction, the temperature, the insulation and the presence of (moist attracting) salts.
Rising damp: the cause
Rising damp occurs primarily in older houses that predate world war II. Most of the times it is due to the masonry style of old foundations and the lack of closed layers between the foundation and the walls. Because nowadays foundations are of concrete, this is less likely to happen.
The rising of damp is a slow process that usually just gets discovered after decades. The ever-changing groundwater levels and the presence of salts in the masonry have the biggest influence on the speed and on how high the rising damp might rise in the walls.
Rising damp is not always caused by the direct contact between the foundation and ground or surface water. It can also be due to the horizontal supply of moist from the surrounding ground.
Rising damp: the consequences
Most of the time, rising damp gets discovered because it causes mould or moist stains. Besides that, it also produces a stale smell. Paintwork, stucco and wallpaper will fall (let go) in the long term. It is even possible for mould to pass on to the furniture.
Walls can contain so much water on the long term, that they become a Petri dish for algae or similar fungi. Fungi can cause serious wood problems. If transferred to the wood in a building’s core, it may cause severe problems.
Rising damp: the solutions
When damp mounts itself from the foundation into the walls, it typically stores itself first in the crawlspace. The moist increase can be lowered by ventilating and insulating this location. These solutions might stop or, in some cases, entirely clear the rising damp. If it is not possible to ventilate or insulate, applying a layer of sand with seashells might help. This layer is a natural and inexpensive solution, which keeps the moist in the crawl space rather than letting it penetrate a facade.
In old buildings, such as monuments, it is often a necessity to take more extreme measures. These can involve recovering or even completely rebuilding the foundation or walls or removing all the surrounding water-soaked soil. A different option is to impregnate or inject the walls with a unique product, making them water-resistant. A combination of the solutions mentioned above is often necessary.
Borèl offers non-binding advice on how to solve these problems.