Correctly dehumidify cellar
We have been carrying out electrophysical cellar dehumidification since 2010. In this guide, we give you an overview of the possibilities and show you the advantages and disadvantages of the various methods.
Damp basement? This is what you should be aware of
Core statements
- Without eliminating the cause of the moisture, the use of building dryers can lead to an increase in moisture in the masonry in the medium term and thus to lasting damage to the building fabric.
- For sustainable basement dehumidification, the source of moisture must be eliminated and the building fabric must be dried.
- The horizontal barrier is a deep irreversible intervention in the structure and statics of the building, and the masonry below the barrier remains damp.
- With the internal vertical barrier, the wall remains damp on the outside; the external vertical barrier is associated with high costs due to the earthworks.
- Electrophysical wall dehumidification actively combats moisture and is able to dry the building structure down to the basement floor, but may not be strong enough in the case of pressing slope water.
1. What are the causes of damp basements?
The most common causes of damp cellars are capillary rising damp in the walls, condensation and faulty installations. Pressing damp, on the other hand, is very rarely the problem. In most cases, several sources of moisture overlap. For this reason, it is advisable to consult building experts to identify the actual causes of damp. In the following sections, we take a closer look at the individual causes.
- Capillary rising damp in the wall: This effect, along with condensation, is probably the most common cause of damp in the basement. The real reason for rising damp is not wall leakage, but the physical properties of the building fabric. The naturally electrically negatively charged wall promotes rising damp within the wall.
- Condensation: Moisture condenses on cold wall surfaces, where it can cause consequential damage over time, such as mold growth. Condensation is often caused by incorrect ventilation: Warm air can absorb significantly more moisture than cold air. This is why ventilation should only take place when it is cool outside. Otherwise, the warm air will bring moisture into the house, which will then condense on cool wall surfaces, similar to the outside of a cool glass bottle. Another cause of condensation is high humidity caused by showering, cooking or drying laundry.
- Faulty installations: Faulty installations are unfortunately very common. These include external rainwater systems such as water barrels, gutters, downpipes and flat roofs; the poor condition of bricks, stones, mortar, wall bases, rendering, weatherproof paints and silicone joints; weak points in wall construction, such as cracks in brickwork or copings; structures adjacent to the brickwork that conduct water to the brickwork, including leaking windows and doors; the location and condition of vents; chimneys and rain deflectors; mechanical or chemical damp proof courses.
- Oppressive moisture source: Oppressive moisture sources are rather the exception. They are usually a sign that the building was constructed in an unfavorable location. Sources of oppressive moisture include oppressive slope water, springs or water veins near the building, and groundwater that periodically stands high.
2. How to dry a basement?
To keep the cellar permanently dry, both the cause of the damp and the building fabric must be dried out: If the moisture comes from inside, the problem can be solved with intelligent ventilation and dehumidification devices. In less severe cases, targeted shock ventilation may even be sufficient. If, on the other hand, the moisture is penetrating the building from the outside, the leaks must be sealed in addition to dehumidification. There are three ways to do this:
- Vertical barrier: Large-area waterproof barrier layer such as a bitumen coating or slurry plaster seals the wall from the outside or inside.
- Horizontal barrier: injections of a sealant or the installation of a waterproof barrier layer prevents moisture from rising within the wall.
- Electrophysical basement dehumidification: Installation of low continuous electrical voltage permanently removes moisture from the basement wall down to the basement floor.
Rising damp
Principle of the vertical barrier
Principle of the horizontal barrier
Electrophysical barrier
3. Why are dehumidifiers counterproductive?
Dehumidifiers in the form of powerful building dryers are primarily suitable for drying out buildings after water damage or during the construction phase. In contrast, they can have a counterproductive effect in the case of a constant moisture problem, if, for example, the wall absorbs moisture via the capillary suction tension of the building material. In this case, in fact, the construction dryers lead to an increase in salinity, which increases hygroscopy.
As a result, even more moisture gets into the masonry in the medium term. Together with the moisture, other mineral salts enter the masonry. These dissolved salts can crystallize if some of the moisture on the inside of the wall evaporates. On the one hand, this salting of the wall means that the wall can absorb even more moisture. On the other hand, the salts increase their volume during crystallization, which over time causes flaking on the wall surface and lasting damage to the building fabric.
4. What are the risks associated with manual sealing methods?
Rising damp
Principle of the vertical barrier
Principle of the horizontal barrier
Electrophysical barrier
Horizontal and vertical barriers only partially solve the moisture problem: With horizontal barriers, the areas below the barrier, such as the cellar floor, remain damp. Even with a vertical barrier on the inside, such as slurry plaster, the wall can continue to absorb moisture from the outside and from below.
In contrast, the external vertical barrier effectively protects the wall against moisture from the outside, but not against rising damp from below. In addition, the external vertical barrier is very complex and expensive to implement because the basement wall has to be completely exposed.
Even if the horizontal barrier is not quite as complex as an external vertical barrier, it still requires extensive intervention in the masonry, which can affect the structural stability. It is better to refrain from this, especially in old buildings.
5. What are the advantages and disadvantages of electrophysical sealing?
Installation of the electrophysical dehumidification system DRYMAT®
The electrophysical cellar dehumidification with the DRYMAT® system is able to permanently dry both the cellar walls and the cellar floor, even with high moisture levels. An electrical potential is generated with the control unit and the installed electrodes. This counteracts the suction tension in the wall. In this way, moisture can no longer rise in the wall. The residual moisture in the wall evaporates over time. This makes the wall permanently dry.
Thanks to the electrical potential, the dehumidified building fabric does not absorb any new moisture, but remains permanently "sealed" or protected from moisture. The potential of electrophysical drying requires only minimal structural changes and thus brings significant cost savings compared to vertical and horizontal barrier methods. The electricity costs for maintaining the electrical potential amount to approx. 50 EUR per year.
Electrophysical drying with DRYMAT® is also risk-free for people and the building fabric, does not interfere with the building statics, is reversible and therefore suitable for listed buildings. The DRYMAT® system works according to scientifically recognized principles and is certified in accordance with Ö-Norm B 3355-2. Finally, we give you a 10-year guarantee on the control unit and a further 10 years from the ISO:9001-certified manufacturer.
6. How much does electrophysical dehumidification cost?
The cost of electrophysical dehumidification with the DRYMAT® system for a detached house with a floor area of 60 square meters is around EUR 15,000 to 20,000. This amount covers all steps of the job, including analysis, installation and follow-up measurement 18 months after installation. In addition, there are operating costs of around EUR 50 per year, while no regular maintenance work is required.
In comparison, the cost of draining the same property, for example by draining the cellar walls, is around EUR 45,000 to 60,000. The costs for the earthworks are particularly high if external remediation is required. Internal waterproofing costs around EUR 350 per square meter.
7. Conclusion
Basement dehumidification is only successful if both the cause of the dampness is mitigated and the building fabric is dried out. In the case of capillary rising damp within the cellar wall, the use of powerful building dryers can lead to an increase in damp in the cellar in the medium term and to damage to the building fabric.
With the horizontal and internal vertical barrier methods, part of the building structure remains damp. The horizontal barrier also requires extensive intervention in the building fabric. The external vertical barrier is also associated with high costs due to the complex earthworks. In addition, both methods use chemical substances that can be harmful to the environment.
In contrast, the process of electrophysical basement dehumidification with the DRYMAT® system involves fewer risks overall. Only minimal structural interventions are required - without delicate construction chemistry. DRYMAT® is able to sustainably dry out the building substance down to the basement floor. However, the electrical potential is only of limited use in the case of oppressive moisture sources, such as slope water or an excessively high groundwater level.
Contact us without obligation
Do you have any further questions or may we prepare an offer for you?
Get in touch with us without obligation. We look forward to your inquiry!
Get in touch with us without obligation. We look forward to your inquiry!
Tobias Bayer
Managing Director
