Drying out basements and cellars is a more complex task than drying out freestanding walls. The main difference between underground and free-standing (above ground level) walls is the presence of sideways penetrating damp as some external walls are in direct sideways contact with the soil. These walls are thus subject to two main forces:
- Rising damp from the bottom, as walls are standing on the ground
- Sideways penetrating damp as walls are in contact with the soil
In choosing the best solution will ultimately depend on the intensity of the sideways penetration and the intended use of the cellar / basement space. The condition of drainage, pointing and ventilation must also be checked and addressed if necessary as they form an integral part of the solution.
Here are some guidelines on a few typical scenarios and the best ways to solving them.
1. Damp cellar - No running water, no flooding
If the cellar is damp, but without running / liquid water on the walls or flooding, indicates that the cellar is structurally sound and no significant sideways penetration is present.
In these cases our magnetic dehydration system is a great non-invasive and cost-effective option to get the dampness problem sorted or significantly reduced.
What you can expect:
- Free-standing basement walls with no direct contact with the soil dry out.
- Earth-touching walls with a vertical barrier also dry out.
- Earth-touching walls with NO vertical barrier will at least improve or dry out sufficiently to make the cellar fit for storage or even conversion, depending on the amount of sideways pressure. We can advise you better after an initial dampness survey.
2. Very Damp Cellar - With running water, potential flooding
The presence of liquid water on the walls or flooding indicates that the cellar's integrity has been compromised and penetrating water finds its way into the building. These cases require a more complex solution which address both rising damp and penetrating damp, which in this case dominates.
I. Rising Damp
The rising damp problem can be effectively eliminated using our magnetic building dehydration system, which can non-invasively deal with the problem, complementing any waterproofing protection described next, also protecting the upper floor from rising damp. In such cases the dehydration system will have a secondary role and be part of the overall solutions package.
II. Sideways Penetrating Damp
The penetrating damp problem can be solved in several ways:
- BARRIER PROTECTION [Type A waterproofing]: in some forms also known as tanking, provides protection against ground water ingress by applying a waterproofing material
(e.g. cementitious slurry, flexible waterproofing membrane (bitumen, rubber), bentonite clay liner etc.) to either the external and/or internal surface of the walls or floors. Once the waterproofing material hardens it makes the walls watertight on a permanent basis.
If the waterproof barrier is applied from outside the water is stopped at the outer face of the walls, allowing the walls to dry if the internal surface is left breathable. The installation of external barriers involves excavation, which is not always possible due to environmental constraints, limiting the options to a drained protection.
- DRAINED PROTECTION [Type C waterproofing]: involves some sort of cavity drain membrane and sump pump combination. The groundwater is allowed to penetrate the walls and floors which is then collected from under the studded cavity drain membranes via designated drainage channels, routed to a sump pump for disposal.
A WORD OF CAUTION: all these solutions seal the walls so they are non-breathable. Before applying them to old or heritage buildings their impact on the building must be holistically assessed.
Because they prevent the walls from breathing, these waterproofing solutions shift the moisture sideways or upwards, often creating other damp problems such as the appearance of rising damp on the floor above the cellar (e.g. ground floor). The presence of our magnetic dehydration system prevents that from occurring, keeping the rising in check.
Other Influencing Factors
Because cellars are affected by a combination of moisture sources rather than just one single source of moisture, the following aspects also must be checked and any irregularities rectified, as they affect how quickly basement walls dry out:
- Drainage: the condition of drainage is very important for cellar projects and it should be your first point of call. After all, it's easier and less costly to channel away the water from the building than to fight it. In lack of proper drainage, rainwater does not flow away but tends to pool around the walls, resulting in a more abundant sideways water penetration. Lack of improper drainage can be quite easily diagnosed, it is one of the problems we check during our initial survey.
Seasonal high water table problems can also be controlled with adequate drainage, subject to location and surroundings of the building.
- Ventilation: during the dehydration process some of the humidity evaporates indoors and needs to be ventilated out. Cellar walls are often covered by heavy salt deposits as a result of being in contact with the ground. Salts are not only a primary reason behind the crumbling of the building fabric, but they can also capture the humidity present in the air (hygroscopic effect) recycling humidity back into the building fabric. This can slow down or even halt the dehydration of the cellar.
Thus the presence of adequate ventilation is important. Now, this doesn't mean that you have to go overboard and install a costly ventilation system in your cellar. Most cellars have some vents or natural ventilation which allows for air exchange and the passage of moisture.
The surface of the walls is also recommended to be kept free of salts by regularly brushing them off the wall surface.
- Condition of pointing: good quality pointing can be an effective barrier in stopping sideways penetrating moisture, and it is the last defense mechanism before water reaches the internal face of the walls.
We assess all these aspects during our initial survey.