Cellar fungus

The cellar fungus often grows in areas with moist or wet conditions such as groundwork, rising damp or leaking sewer systems or roofs. The cellar fungus grows rapidly and affects both softwood and hardwood. Wood species of sustainability class I are not affected, class II rarely. Because of the consistently high humidity in crawling spaces, these areas are easily affected, as are roof structures in case of leakage.

The spores of the cellar fungus sprout quickly in favourable conditions, after which the fungal threads, called hyphen, penetrate the wood. These hyphen have a diameter between 0.0005 and 0.005 mm and are not visible to the naked eye. Initially, the hyphen are white. On the wood surface, mycelium, entangled hyphae are rarely formed. In some places, for instance under linoleum and behind plinths, a thin degradation can be visible similar to that of dry rot. If mycelium develops on the surface of wood or stone, this only consists of thin hyphen of 1 to 2 mm that branch out in a fan-shaped manner and that look like roots or vines and have a dark brown to black colour. Fruiting bodies are rarely found in buildings. Initially it consists of an ochre coloured thin plate of about 3 mm, which later turns olive brown, with an irregular shape, covered with small nodules. It may vary in size from several centimetres to over 50 cm in diameter. The edge remains yellowish white. The spores created by the fruiting body, are dark brown, oval and very small, with a length of 0.008 to 0.0013 mm and a diameter of 0.005 to 0.009 mm. They spread through the airflow or insects, which completes the cycle.

The cellar fungus is family of the brown rot inducing fungi. The degradation of cellulose and hermicellulose, destroys the walls of the wood cells. At first, the wood has a dark discolouration that can turn almost black in an advanced stage. Characteristic are the cracks that run in the fibre direction of the wood. This is often visible in smaller wood, such as in windows and frames, whereas in larger wood, such as beams cracks will also be visible, perpendicular to the fibre direction, causing cube-shaped elements similar to the damage caused by dry rot, but less sharply defined.

Internal deposits
Another important characteristic of the cellar fungus is the interior deterioration of the wood, in which a thin layer of 3 to 4 mm of healthy wood remains in tact at the surface. Even in an advanced stage, often just a small deviation and discolouration of the surface is the only signal that the wood has been affected by cellar fungus. For non-experts, the cellar fungus is hard to identify.


Cellar fungus

Not only because of the germination of the spores can wood be affected by cellar fungus, but also by hyphen of previously inflicted damage. Cellar fungus affects wood with a moisture level of 40 to 60% with an optimum of more than 50% In 21 degrees it develops the fastest, and in 35 degrees it still shows minor growth. In 0 degrees the growth stops, but even -30 degrees won’t kill it. For a treatment against cellar fungus or other fungi, please contact the EWS.

Dry rot

When wood processed in buildings has a moisture level of more than 21% for a prolonged period of time, it is likely for fungi to grown on and in this moist food. The most prevalent wood harming fungus in the Netherlands is the Serpula lacrymans Both conifers and broad-leaved trees can be harmed by these fungi. The fungus can exist in beams and / or other wooden parts of the ground floor flooring. On or in wood outdoors, the dry rot is hardly ever found.

Appearance / Lifestyle
Wood affected by dry rot has a brownish discolouration. As the wood is affected further, it turns soft and loses its strength. An an advanced rotting stage, the wood is brown with deep parallel shrinkage cracks perpendicular to the fibre direction.

The fungal threads in the wood cannot be seen by the naked eye. These threads penetrate the wood to a very deep level. The cross-section of such threads is very small, just 0.0016 mm. At the surface of the wood the fungal threads are usually somewhat thicker, and sometimes visible in the form of white flakes. Fungal threads don’t just exist on wood, but also on stone or concrete floors of basements for instance, and in and on damp walls etc. Sometimes bundles of fungal thread are found with a diameter between 5 to 8 mm. These are called strands, and are white at first, and later turn grey.

In places where the fungal threads grow in the wood, substances are formed that degrade the cell walls. A portion of the wood is converted into carbon dioxide and water by the fungus. In this process, energy is released that is used for the growth of the fungus. Even dry wood can be affected, because dry rot is able to transport moisture from moist places using the fungal threads. After a while, fruiting bodies are formed on the wood or wall, consisting of compact tissue. The fruiting bodies are fairly flat, 1 to 3 cm, thick, brown with a white edge and vary in size from several centimetres to 1 meter. The fruiting bodies form the base for the spores that cause the species to spread. A fruiting body can form billions of spores. Large numbers of spores together look like rust-brown powder.

Dry rot develops the fastest in temperatures of 23 degrees Celsius. In 28 degrees C. or higher, the fungal threads die off. The spores however can withstand higher temperatures. At freezing temperatures the fungal growth comes to a halt, but the dry rot doesn’t die. After the frost period, the growth simply continues.

Prior to control measures, it is important to take all possible measures to prevent leakage, condensate, rising damp, resounding walls, water entry or high ground water levels. After the control measure, the wood should not be allowed to get moist again, because that would make it appealing for dry rot again.

The wood affected by fungus must first be removed. In addition, the adjacent, not visibly affected wood across a length of 1 meter must be removed and replaced, preferably with wood pre-emptively treated with a fungicide. Affected elements that cannot be removed must be treated with a curative agent, such as azaconazole or tributyltin phosphate. It isn’t simple to impregnate the wood with the necessary amounts of the substance in such a curative treatment. For that reason, the treatment must sometimes be carried out twice.

Walls that may contain fungal threads must also be treated. Loose stucco must be removed and the joints must be scraped out. Afterwards, the walls must be treated with the agent.

In case of serious deterioration due to dry rot, it is recommended to drill diagonal holes downward in the holes. The depth of the holes must be 2/3 of the wall thickness, 30 cm apart and 20 cm crosswise to each other. Afterwards, the drill holes are injected with the fungicide several times in a row. After drying, stucco can be applied to the wall. For a treatment against dry rot or other fungi, please contact the EWS.