Treats wood mold

Mold on wood - formation, removal, prevention


Why does mold develop on wood?

This question is easily answered. Wood provides mold with many nutrients in the form of cellulose and lignin, which the fungi can metabolize. In addition, for example, construction timber that was installed too damp provides the mold with the necessary moisture so that it can grow.

If there is still standing air, the conditions for the mold to grow on the wood are perfect. So there must be nutrients, moisture and little air movement for the wood mold to grow.

Is mold in the wood a problem?

Well that depends. There are roughly three areas ...

  • Mold on structural components
  • Mold on non-structurally relevant components
  • Wood mold as a cosmetic problem

Any mold on wood that appears on furniture, visible wood paneling, etc. is usually a purely cosmetic problem. Structurally irrelevant components such as wooden floors, ceiling paneling or non-load-bearing studs in wooden houses, etc. are definitely a building biology problem, as mold on the wood can also spread to any adjacent load-bearing parts. But they are not an acute danger for structural problems. Mold on wooden parts that have a structural load-bearing function (e.g. ceiling beams, half-timbered beams or load-bearing roof structures) are to be viewed as critical, as the load-bearing capacity is impaired by the mold in the wood in the event of a long-term infestation can be. The cell structures in the wood are destroyed by many wood fungi.

However, not every mold on wood is a wood-destroying fungus. Many types of mold discolor the wood surface (or the inner part), but leave the cell structures intact, so that no problems are to be expected from a structural point of view.

Other types of fungus, on the other hand, are dangerous, as they can often cause considerable damage to the building fabric in just a few months and thus often cause high costs for renovation work. A short selection of wood-destroying fungi is listed here. Some of these species are covered in detail in further articles on this website. See list at the end of the article.

The following wood-destroying fungi are specifically mentioned ...

  • Real dry rot
    Probably the most aggressive and most difficult to control mold on wood that thrives in our latitudes. The infestation by dry rot must be reported nationwide to the building authority!
  • Brown cellar sponge
    A typical fungus that can be found in new buildings with wood that is too damp. It grows very quickly, but is not as destructive as the dry rot
  • Leaflet
    Only infects coniferous wood and usually does its mischief for a long time undetected under the surface of the wood. This wood mold can often be found on old wooden windows, for example.
  • Big bark sponge
    Likes to grow on pine wood (but other softwoods are also attacked). Often found on roof beams that are too damp. Only attacks the sapwood and not the core in the wood.

All mushrooms (with the exception of the real dry rot) have in common that they need a fairly high level of wood moisture to grow. Wood mold can usually only develop when the wood moisture is above about 25%. The dry rot can, however, also grow at lower moisture levels; it only needs a high level of subsurface moisture to develop. If the wood dries out, most types of mold can go into a dry rigidity for years and will simply continue to grow when the moisture is renewed.

How to remove mold from wood - what can you do?

If furniture or other visible parts in the apartment are affected, the biggest problem is usually to remove any discolouration in the wood. Many fungi penetrate the wood structure, so that a complete removal of mold in the wood is only possible with mechanical processing (sanding, planing, etc.) of the surfaces. If this option is not available, you can either try to treat the surface with a cleaner containing chlorine, or you can use hydrogen peroxide solution. Both variants bleach the wood surface and can possibly restore a correspondingly attractive surface. But be careful when handling these chemicals, they can be extremely irritating to the skin and eyes. Always use in the apartment with the window open. In any case, do a test on an invisible corner to determine how the subsurface changes.

If the building fabric in the house is affected, a specialist should always clarify which mold is at work on the wood. In order to then have appropriate countermeasures carried out. Fighting mold yourself is only useful for smaller, clearly demarcated infested areas, as it is necessary to clarify what the causes of the mold infestation on the wood are.

Prevent mold on the wood

As already mentioned above, the cause of the wood mold must always be determined, otherwise all removal measures only help in the short term. To ensure better air circulation behind furniture, you should move the furniture about 10cm away from the wall in the future. Moisture created by condensation can dry off better and the wood mold is deprived of its livelihood.

All wood to be installed in the house should always have a humidity of less than 20% before it is installed, or have enough opportunity to dry off while it is installed. In many cases, wood that is installed too moist is irresponsible, regardless of the mold, as shrinkage during subsequent drying can cause connections between wood to become wobbly and, depending on the situation, undesirable drying cracks can arise.

All wood parts in contact with the ground should always be provided with insect and mold protection, which can protect the wood from infestation in the long term. Wooden parts that could be exposed to penetrating water on external facades in extreme situations should also be treated in the same way.