Mold rot

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Soft rot is a form of wood rot that is caused by various fungi (especially Ascomycetes such as the fire crust fungus and Deuteromycetes ). In contrast to the brown and white rot, the soft rot has a very high need for moisture. Therefore, this form of rot occurs on wood that is permanently exposed to moisture. Woods that are installed or stored outdoors and are therefore exposed to very high levels of moisture are particularly at risk . The risk of mold rot infestation and thus damage to the wood is also increased by direct contact with the ground (e.g. with wooden posts and masts, even trees with roots in well-watered soils) increased considerably.

Damage

Wood destroyed by rot, dried

Rot-damaged wood shows a greasy, blackish discolored surface when wet. After drying out, the wood surface takes on a broken cube structure , which is similar to brown rot , but is much finer and often limited to the immediate surface (up to a few millimeters deep).

The mildew pathogens cause a breakdown of the cell walls and consequently a considerable loss of strength in the wood. Even if the rot damage can only be seen with the naked eye on the surface, the entire wood cross-section can be affected by the loss of strength.

Mold rot is treacherous in that affected wood can suddenly break through when exposed to stress and without warning, while in intact wood an overload is initially noticeable acoustically through creaking, crackling and / or cracking.

At the microscopic level, the damage pattern shows a clear difference to the other two forms of wood rot. The soft rot forms diamond-shaped caverns within the secondary walls.

prevention

The best protection against mold rot and other wood-destroying fungi is to design constructions in such a way that wood is not exposed to increased moisture or direct contact with the ground. If this cannot be avoided (if the hazard class 4 according to DIN 68800 Part 3 is present), then, as a rule, load-bearing structures should be treated with a chemical, etc. a. Wood preservative effective as a preventive measure against mold rot is required. A special feature of soft rot, which must be taken into account when protecting wood , is its tolerance to chromium-fluorine salts. However, many types of fungus are very sensitive to wood preservatives with copper compounds.

An alternative option is to use types of wood with sufficient natural durability . For the installation situation in hazard class 4 described above, woods with resistance or durability class 1 according to DIN EN 350-2 would have to be used. However, there are only a few (expensive, mostly tropical ) types of wood that can be used for this.

literature

  • Tobias Huckfeldt, Olaf Schmidt: House rot and timber fungi. Verlag Rudolf Müller, Cologne 2006, ISBN 3-481-02142-9 , 377 pp.
  • Olaf Schmidt: Wood and Tree Fungi. Springer Verlag, Berlin Heidelberg, 2006, ISBN 3-540-32138-1 .