Problems. Causes. Solutions.
The musty, mouldy smell inside a humid basement may be annoying, but most people regard it as harmless. In fact, however, a wet basement does not only constitute an odour nuisance but also a genuine health risk, because moisture also attracts mould. Problems, causes and solutions for a wet basement – let’s get to the bottom of the matter:
The simplest cause: a leaking water pipe
If it is not necessary to open a wall for sealing the leaking pipe, this problem can usually be remedied quickly and inexpensively. For other causes, the matter is often more complex.
Cause: missing horizontal sealing
If the basement walls are humid, this may be due to a missing horizontal sealing against the soil, particularly in older buildings. It can be added subsequently, for instance by slitting up parts of the brickwork at the inside or outside and inserting metal sheets.
Cause: missing or overcharged drainages
If the groundwater level is high and water penetrates into the basement through the light shafts of the basement windows, or if seepage water collects on slope properties and intense rain cannot flow away, this may be due to missing or overcharged drainages. To ensure a permanent and optimal functioning, TÜV experts recommend to have drainages maintained and flushed by a specialist every 10 years.
Cause: wrong ventilation
If the outdoor temperature is high, basements should never be ventilated during the day. This is because warm air stores more moisture than cold air. And when the air inside the basement cools down in the evening, the moisture condenses at the cool wall.
Cause: defective protective coating
There is also a risk of vertical moisture penetration caused by defective protective coatings. Bitumen, for example, which is used to seal the basement construction, decomposes after only 30 to 40 years. Renewing the sealing is generally a very complex task because the external walls must be dug up to the bottom plate and sealed again.
Cause: blocked roof outlet
If a humid stain appears in a corner of the basement again and again, this may be due to a blocked roof outlet system on the outside wall: rainwater running off accumulates inside the gutter and will sooner or later penetrate through the wall. That is why gutters and downpipes should always be empty. If humid spots have already formed on the walls, the use of a construction dryer should be considered in order to prevent consequential damages.