amp basement after a flood? Dry the wet basement. But how?
Wet cellar? Damp walls? What should I do? Tips on drying and dehumidifying

If the basement and living rooms show wet masonry after a flood, quick action is required. After removing all soaked objects, the floor covering – and possibly also the wall cladding – it is extremely important:
Dry the building fabric – as quickly as possible!
The moisture MUST be removed from the masonry and floor – this is the only way to prevent consequential damage such as mold and dust lice, harmful bacteria and germs. In some buildings, without drying, the statics would even be at risk, because too long exposure to moisture affects the masonry!
Can the damp cellar be ventilated and fans dried?
Limited. Especially in summer, the cool cellar is a “moisture trap” when outside air with high temperature and humidity is brought in. The humidity condenses on the cool cellar walls – and forms a barrier that prevents the damp masonry from drying out. If you want to dry with fans – make sure that the air output is very high. Only then is it possible to remove moisture at all. Small fans or even just tilt window ventilation is extremely unsuitable – and massive mold growth can result. However, ventilation is nowhere near as efficient as installing air dehumidifiers with SMF particle filters.
These devices work as circulating air dehumidifiers. So you do not need an external wall connection and no air piping.
How does cellar drying work with building dryers?

The dehumidifiers are placed in the damp basement. The air is circulated with an integrated fan and passed over a condensation surface on which the air humidity condenses. The water collects in a container that can be easily emptied. Dehumidifiers and building dryers with SMF filters also bind germs and mold spores to a filter surface. This prevents contamination of the room air through the spread of germs.
With this process, the air humidity is gradually reduced. By lowering the air humidity, the drying layers of air tend to saturate themselves with moisture – and thereby remove the moisture from the wall and the building structure. Successive and sustainable! This process takes time – but it is many times faster than ventilation measures!
ABOVE ALL: The humidity is kept CONSTANTLY reduced – and this counteracts any mold formation!
How long does it take to dry a cellar after a flood?
The drying time depends on many components: the wall thickness, the degree of moisture penetration, the material of the wall, the thickness of the screed, etc. For water damage drying, normally 1 building dryer is positioned per approx. 25 m2 of surface. The drying time then usually takes 4 to 12 weeks. Of course, you can also dry with a smaller number of dehumidifying devices and move the device (s) from room to room. Every one to two days. The drying time is then longer – but the costs for rent or purchase are cheaper!
Rent a construction dryer – or buy? What makes sense
In the first phase, rapid drying using a rental dryer is advisable. After removing most of the moisture, you can switch to a single dryer. Experience has shown that the residual moisture diffuses out of the masonry over a longer period of time. Therefore, after the initial drying, you should consider buying a device for long-term dehumidification. In order to reduce germs that inevitably penetrated the rooms during a flood, it should be possible to equip the dehumidifiers with SMF filters or HEPA adapters. Long-lasting and sustainable SMF dehumidifiers are available from specialist retailers from around EUR 600.00.
Water in the insulation layer under the screed
If water has penetrated into insulation below the screed, there is no avoiding professional help. In these cases, extensive drying of the underbody with special blowers / compressors and large-scale dryers usually has to be carried out. In the event of a large-scale damage event, however, the specialist companies will be fully utilized. Thus, the mentioned installation of drying devices remains as an initial measure in order to prevent further damage. If the drying of the surface of the building does not achieve sufficient drying of the floor, then the insulation layer must be dried. However, insulation layer drying can be very complex. The costs for a professionally carried out drying move for 50 m2 of basement area between EUR 1,000 and 3,000 – depending on whether accompanying measures such as B.Faecal germ removal in the subsoil, required or not. With these costs, it is necessary to estimate whether a core renovation – i.e. removal of the subfloor and renewal – is possibly more cost-saving than drying the insulation layer. In this case one is limited to the installation of building drying devices. You will find a schematic representation of the processes used to dry the insulation layerHERE . In serious cases – especially if faecal germs / sludge got into the insulation layer, a complete removal will have to be considered….
Dehumidify – or do you prefer ventilation?
Ventilation in the basement can be problematic, especially in summer. In addition, an excursion into physics: warm air can absorb more water vapor than cold air.
If warm air gets into the basement, this air cools down and can no longer hold the amount of water vapor it contains. The excess moisture settles on the walls. Mold spores find optimal colonization areas on this film of water.
Most of those affected try to get the problem under control through frequent and long ventilation. At first glance, this seems conclusive, but at second glance, this action is unfortunately counterproductive.

With more ventilation, more moisture comes into the basement from outside. There is increased condensation on the cool cellar walls .
What should be considered when drying a damp cellar? For ventilation, the outside temperature should be lower than the basement temperature, which is why autumn and winter are ideal for ventilating a basement on dry days.
Therefore: fans and ventilation after a flood can (to a limited extent) be recommended for LIVING ROOMS . For cellars, however, it is essential to ensure suitable drying – ideally with building dryers and SMF particle filters to prevent germ formation !