Reasons for mold appearance on the barrel sauna

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Reasons for mold appearance on the barrel sauna

Wood is a natural material that is not only environmentally friendly and aesthetically attractive but also has good hygroscopic properties. Wood quickly absorbs moisture, forming a very favorable habitat for fungi, mold, microorganisms, and insects.

The reasons can be as follows:

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1. Bioactive outer environment

The main reason for mold appearance and growth is the high moisture content in the air. For example, frequent rains or the location of your site near a water reservoir beneficially influence the active appearance of mold. A high risk of mold growth is thought to occur at the humidity of 70-80%. Mold fungi are everywhere: they can be found in air, soil, and even in water. So, the appearance of mold on unprotected materials is inevitable under such conditions.


Antiseptic impregnation helps protect your barrel sauna from mold, rotting, and maintain its well-kept look. These are unique products that do not form films on the wood surface, i.e. do not prevent it from breathing.

To extend the service life of wood, it is recommended to treat surfaces with a protective impregnation at least once a year. You should choose the impregnation, on which it is indicated that it has to be used under the conditions of barrel sauna installation (corresponding temperature and humidity).

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2. Ground moisture

The formation of mold in the lower part of a barrel sauna can occur primarily due to installation faults. The barrel sauna weight can vary from 500 kg (for the 1.6 m model) to 1500 kg (for the 5 m model), so customers do not always install the structure on a flat foundation. Mold often appears on wooden products where they constantly contact with soil.  If dirt is not removed from the façade for a long time (especially in warm and wet weather), mold spores will have a chance to set tight and grow quickly on the surface.


The excessively moist ground is an excellent place for moss and mold growth. If you find a lot of moss in your garden when cleaning your lawn, we strongly recommend installing a barrel sauna on a flattened area filled with gravel or concrete foundation, but at first, remove the top ground layer (at least 10 cm).

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3. Improper care of the barrel sauna

Barrel sauna is designed to avoid the appearance of microorganisms at maximum: dry air inside the steam room, high-temperature conditions, no corners. However, long periods of downtime without any air circulation, shade, lack of ultraviolet rays, use of water in the barrel sauna, and lack of regular ventilation can be factors causing the mold growth.


  • Check the ventilation cleanness and condition regularly (keep ventilation holes open)
  • Ensure that your barrel sauna is fully ventilated after procedures have been taken. It is necessary to leave doors and windows open. Ventilation is required at any time of a year!
  • Don’t leave wet towels, brooms or any other wet things in your barrel sauna.
  • The ideal solution is to allow the access of sunlight through at least small windows.
  • Regularly wash your barrel sauna thoroughly! There are special household cleansers for saunas. For example, Finnish detergents Harvia Sauna, Tolu and others. They are applied with a sponge and cleaned off with warm water. Common water rinsing is not effective.

The usage of cheap materials and breakdowns of construction technologies result in additional expenses, as they are often covered with fungi.

The easiest and safest way is to buy an outdoor sauna under the manufacturer’s warranty.

We are sure about the quality of our products and offer a 2-year warranty on outdoor saunas and all elements.

Our goal is excellent quality at a reasonable price!

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