Fungi attacking wood

To better understand the threat posed to wooden structures by fungi, let’s start with a bit of biology. Fungi feed as parasites or saprophytes, meaning they require substances accumulated by other organisms to survive. Another important factor necessary for their growth is high environmental humidity. The body of a fungus is composed of thin, often colorless threads called hyphae. This system of hyphae forms a mycelium that grows through the infected structure. The hyphae are invisible to the naked eye. Their presence is only revealed when we notice wood decay.

Conditions for the growth of fungi

For fungi to thrive in wood, they need:

  • Food: in the form of unprotected wood
  • Adequate temperature: 5-35°C
  • Access to air
  • Adequate wood moisture: 20-90%

Based on the above factors, drying and impregnation are two simple methods of protecting wood from fungi.

Recognition of wood infection by fungi

Based on the type of wood decay, fungal infections are divided into:

  • Brown decay
  • White decay
  • Gray decay
  • Blue stain of wood

Brown decay

Grzyby w drewnie
Brunatny rozkład drewna

It poses the greatest threat to construction. Initially, infected wood turns brown, then becomes brittle and cracks, forming prismatic cubes. Finally, the wood turns to powder.

White decay

Grzyby atakujące drewno
Biały rozkład drewna

Also known as white rot, infected wood turns white and becomes softer while retaining its dimensions. Heavily infected wood bends and crumbles under finger pressure.

Gray decay

Szary rozkład drewna

The least dangerous of all types of infections, it causes destruction of wood tissue. The surface is significantly altered, but the infected layer extends 2-4 mm into the material. This decomposition is relatively slow and requires high wood moisture content (approximately 80%). This means that elements exposed to constant moisture are most susceptible to this decomposition.

Blue stain of wood

Sinizna
Sinizna

The sapwood part of the wood turns a bluish-gray color, a very common phenomenon. Besides the obvious aesthetic impact, the mechanical properties of the wood remain unchanged. In other words, the strength of wood infected with blue stain is not reduced. Wood is most often attacked by blue stain fungi when it is still round in storage or freshly sawn, and its moisture content is between 35 and 80%.