Treats wood rot in concrete

The variety of wood-destroying fungi: Is it good if it's not a real dry rot?

The key question when you find "rotten" wood in your house is: Was or is that it Real dry rot , Serpula lacrymans, or another mushroom?

The process of a proper control differs according to this.

An infestation with real dry rot usually results in strong growth through the masonry and other mineral building materials, which makes a combative sponge restoration costly.

Other wood-destroying building fungi do not have such growths or they are less pronounced or easy to remove. To combat this, it was sufficient to replace the destroyed beams and permanently and effectively eliminate the causes of moisture in the wood. Only in a few individual cases with ingrowths in mineral components might additional preventive chemical treatment be necessary.

A determination of the fungus species to exclude the real dry rot and related species from the other wood-destroying fungi is therefore absolutely necessary, because according to DIN 68 800 Part 4 Section 4 Paragraph 2.1. to be noted:

  • without an unequivocal determination of the fungus species, the control is to proceed as with the real dry rot
  • the species related to the dry rot should be treated like the real dry rot.

According to current teaching (Schmidt 2003), the only species related to the real dry rot is Wild dry rot,Serpula himantioides. It has to be treated like real dry rot as intended, so it is essential. In the building, however, it occurs extremely rarely, e.g. on the plastered framework near leaking drainage. In the open air it can be found on dead wood, where it is more common and also in greater spread. Its then numerous fruit bodies are much smaller and thinner than the real dry rot. When viewed under the microscope, the strands can hardly be distinguished from the real dry rot.

Wild dry rot on lying dead wood (pine), young dried out fruiting body. Photo: Rüpke
Typical fold (merulioid) of the wild dry rot on the dried out fruiting body. Photo: Rüpke
Vessel hype from wild dry rot with bars (no difference to real dry rot!) Photo: Rüpke

The wrinkle skins are not related to the dry rot. They can be found in buildings Little onesWrinkled skin , Leucogyrophana pulverulenta , the Sclerotia wrinkled skin , Leucogyrophana mollusca and the Pine wrinkle skin,Leucogyrophana pinastri.

All Leucogyrophana species have a higher moisture requirement than the real dry rot. They show a clear brown rot (crushed powdery, cellulose is broken down, lignin remains) with a broken cube similar to the real dry rot. The differentiation from dry rot is often not easy and requires a microscopic determination.

As intended, the types of folds are to be treated like wet rot fungi, i.e. only to a limited extent.

Sclerotia wrinkled skin ,Leucogyrophana molusca , larger fruiting bodies grown on a mineral base. Photo: Thumper
Strands of Leucogyrophana pulverulenta on oak, young, embedded in surface mycelium. Photo: Rüpke
Resembles the real dry rot, a vascular hype from Leucogyrophana pulverulenta. The difference is, for example, the missing fiber hyphae. Photo: Rüpke
Young infestation by the pink juice spore on a wooden frame component as a result of moisture spreading in the wall. Photo: Herff
Otherwise rather seldom, as a result of increasing, densely packed energy-saving construction methods, the damage pattern of the Pink juice porlings , Oligoporus placenta occur in the building . The brown rot pathogen on coniferous but also on hardwood has a high moisture requirement and is to be expected especially in the case of condensation damage in wooden structures. Moisture penetration of the insulation material is often the cause of infestation.

This is a building fungus that appears regularly and frequently (2nd place) with often great damage to wood Spread out house porling,Donkioporia expansa.

It belongs to the group of white rot pathogens (more precisely: simultaneous rot), which means that the fungus "eats" mainly the lignin from the wood and only leaves the cellulose. (The wood compared to reinforced concrete: lignin would be the concrete and cellulose the steel reinforcement).

This makes the wood very fibrous and light like balsa wood. In addition to oak, coniferous wood is also infested, provided there is a necessary source of moisture in the building. The spread house porling can compensate for dry times. As a result, sewer pipes are leaking

The fruiting body of the spread house lobster has clear pores on the often gray top and a corky leather-like consistency. Its destructive power often leads very quickly and not only on oak, but also on coniferous wood up to a total loss. In relation to e.g. the real dry rot, which often causes only minor damage to the edge of the oak, its destructive power is incomparably greater and covers the entire oak cross-section.

You can find another interesting, well-hidden case of damage to the Spreading House Porling here. It is interesting how this damage and its cause was found non-destructively without opening the component.

Damage to the roof is often the cause of an infestation on the purlins of the wooden structure by the Star set mushroom , Asterostroma spp., also a rarer wood destroyer on softwood.

This wet rot pathogen produces an intense white rot and can be safely recognized under the microscope by its own "star set". The damage to the wood is often considerable. The fungus can also be found in or on the masonry. -> see the damage cases

Less often one encounters the damage on the building Two-colored resin bark mushroom , Resinicium bicolor, which can be recognized under the microscope by its typical star system.

The finger-jointed glued wood affected in the picture on the right is spruce. The second wood-destroying fungus was the wood-leaved Gloeophyllum trabeum found.

In late spring it comes to fright in wet rooms (baths) if suddenly and unexpectedly a Meat cup , Peziza spp ., grows out of the joints of the tiles. Underneath there is often a chipboard that is already completely moistened and dissolved in its initial chips, which the fungus eats. The fungus is a sure sign of pronounced (but often invisible) moisture damage, not infrequently after previous construction errors. His presence in the bathroom is an occasion to open the floor and build it up again after the source of moisture has been found and removed. That is the only sensible fight. Any poisonous substances against the Peziza species, otherwise known as edible mushrooms, are unnecessary here.

Left picture: fresh meat mug, Peziza spp. in the bathroom. A very humid climate is a must. The infestation is usually an indication of moisture damage, often after construction defects. Right picture: here the meat cup grows - in a completely different way than usual - out of the joint of a brickwork. Photo left: Rüpke, photo right: Ibold

The same applies to another representative of the white rot pathogens, the

Oyster mushroom, Pleurotus ostreatus, on a new insulation facade. Photo: Thumper
Oyster mushroom , Pleurotus ostreatus that we find now and then (more by chance) on the building.

He is one of the oatlings. Their traditional area of ​​life is otherwise more weakening or dying hardwood, to which they quickly and thoroughly damage caused by a white rot. But amn knows them better as tasty edible mushrooms.

They often grow out on the plaster or on the masonry, if there is a corresponding nutrient substrate.

In the picture on the left, it grew out of a highly modern thermal insulation composite facade. For us it is a tasty indicator of damage, because behind it it must be sufficiently moist and - as I said - also provide a nutrient substrate ...

Another representative of the oyster mushrooms, the lung oyster mushrooms, occasionally occurs as a wood destroyer in the human living environment.

Actually, one does not suspect any fungal attack on green impregnated timber. The two following pictures show the opposite. Apparently, the builders' limitless trust in the green color was the reason that the timber merchant was able to sell this defective lumber after all .


Older surface mycelium of the brown cellar sponge, spin-like adherent.
Photo: Rüpke
The beginning of the cube break of the brown cellar sponge, a brown rot pathogen.
Photo: Rüpke

Some people get shocked when a web of black threads appears on the wall in the dark cellar light. It is the typical mycelial network of the, mostly based on a leaning wooden part Brown cellar or wart sponge , Coniophora puteana. It overgrows masonry and plaster, and can possibly also grow into them.

The fresh mycelium, which is the opposite white, can be confusing. Together with the damage caused by a "brown rot", it can easily be confused with the real dry rot.

Brown cellar sponge on the cellar wall, old, rooty. Photo: Rüpke
Brown cellar sponge, white when young, under flooring on chipboard. Photo: Rüpke

One might think that brown cellar sponge can typically be found in the cellar. But it can also be found on the higher floors of a house, e.g. under dripping cold water pipes or near the damaged roof. In contrast to the real dry rot, it requires a significantly higher wood moisture content, if possible> 50 - 60%. If it becomes permanently dry, it dies quickly.

It often occurs together with the white pore sponges, Antrodia spp. on, e.g. with the Broad-pore white pore sponge,Antrodia vaillantii a uf, which needs a lot more moisture in relative terms. Its white mycelium can be similar to that of the real dry rot. It can also be found in and on the masonry. For this purpose, a case description and a reader inquiry "Cellar sponge in the clay ceiling".

The white pore sponge welcomes wood built into the outdoor area. A pressure impregnation does not bother him after he has chemically cracked the fixation himself. Photo: Rüpke
A look into the opened wood reveals a white fruiting body. The high moisture content in the wood built into the ground is just right for the white pore sponge. Without a cover, there is a good supply. Photo: Rüpke

The white pore sponges have a good life thanks to the large amount of wood built into the ground in gardening and landscaping. These fungi made seasoned experts faint when it became known that they had successfully overridden the chemical wood protection that had been used against them in the boiler pressure process. They actively cracked the chemical fixation, which is supposed to prevent the active substance (poison) from being washed out, and were then able to calmly destroy the wood. The wood preservative chemists now had to upgrade against it. The overgrowth of modern mineral building materials such as cement fiber boards e.g. by the Narrow-pore white pore sponge , Antrodia sinuosa, sometimes surprise.

This also includes a less common fungus that causes brown rot, the Yellow pore sponge , Antrodia xantha. He constantly demands high humidity. Its destructive power is rather moderate. The yellow pore sponge, Antrodia xantha, is also often found together with the brown cellar sponge.

Yellow pore sponge, pore layer of the fruit body with 3-5 pores per millimeter. Photo: Rüpke
Yellow pore sponge, small, bulbous fruiting bodies with only a few pores. In the center of the picture all white woolly aerial mycelium. Photo: Rüpke
That the Mussel crimping (Pit / fan sponge), Paxillus panuoides, has a very high moisture requirement, as evidenced by its popular name "pit sponge". Today we find a mine-like climate in the building construction after faulty thermal insulation (mostly leaky vapor barriers or if it is located on the cold side). It is therefore not surprising to find the mussel kremling in buildings today, audibly in such incorrectly insulated loft constructions. The mussel krempling can only be found on the wood. Supposedly found on the masonry or plaster, it is usually a type of mushroom, such as the fluted mushroom, Pleurotus cornucopiae or the oyster mushroom, Pleurotus pulmonarius.

The Scaly saw blade , Lentinus lepideus , occurs more outdoors, prefers hardwood and often causes damage, e.g. to railway sleepers, through white rot.

Such mushrooms growing on the ceiling are at first a mystery to the explorer. These are harmless ones Inks that indicate high humidity and indicate water damage. Photo: Rüpke

The Inking , the genus Coprinus, amazes the viewer when he finds it in buildings. They usually grow out of the ceiling, wall or floor without any wood being found nearby. They are commonly called dung mushrooms. But be careful, this small, harmless fungus is an indication of water on the building structure and it is not uncommon for severe damage to be found nearby. Therefore one should always take this fungus seriously and consider it as a helper in the search for building damage.

The ink in the bathtub, on the one hand very funny, but here something is wrong with the building structure.
Even if a tint grows out of the ceiling through the plaster as here, (severe) structural damage will be hidden behind it.

In addition to the wood-destroying fungi that were economically important after the damage, there are also the Fir and fence leavesGloeophyllum abientinum, G. sepiarium , which are mostly to be found in the first link (window mushroom) when windows and outside wood are destroyed. Both are softwood specialists, the first on spruce, the second on pine. The difference is that Wood leaflet , Gloeophyllum trabeum , which also attacks hardwood (e.g. oak). All of them cause brown rot and are feared on load-bearing components. They destroy wood from the inside out unnoticed.Fruit bodies appearing on bridges and roof structures mean an acute risk of collapse! Condensation due to thermal bridges on metal components built into the wood is often the (invisible) cause of the infestation.

There are also lesser-known mushrooms like that Large-pored fire sponge ( also: cinnamon-brown pore sponge ) , Phellinus contiguus which apparently rarely occurs in our country, but causes greater damage in neighboring countries to the north. It may be that it is only less popular with us because of the lack of awareness.

Phellinus spp. on the weather side of a softwood framework. Probable cause was n.a. Contamination of condensation in the (too) tight compartment. Photo: Rüpke
Phellinus spp. on the softwood flooring of an attic, above with damage to the roof covering. Photo: Rüpke

Rarely on the building, more in its surroundings (trees) you will here and there come across a strange type of pitch-black, charred-looking strand mycelium on the deadwood. Then you have to do with mushrooms of the genus Armillaria (Hallimasch) , the main causative agents of stem and root rot. Mostly starting from dead wood, wood residues or left tree stumps, such rhizomorphs grow through ( R.subterranea ) the soil and lead to white rot on the trees. Because of its enormous spread, this mushroom is probably the largest and oldest living thing on earth.

The black strands of the Hallimasch can be discovered under the bark of this deciduous tree stump that remained next to the building. Photo: Rüpke
After the bark is removed, you can see the rizomorphs. This is the cord mycelium of the honey fungus that continues in the ground. Photo: Rüpke


O. Schmidt, Holz- und Baumpilze, Springer, Berlin, 1994
V. Rypacek, Biology of Wood-Destroying Fungi, VEB Fischer, Jena, 1966
G. Langendorf, Holzschutz, VEB Fachverlag, Leipzig, 1988
E. König, Animal and plant wood pests, Holzzentralblatt_Verlag, Stuttgart, 1957
M. Wishes, sponge in the house, Deutscher Verlag, Berlin 1952
T. Huckfeldt, O. Schmidt, Holzfäule- ad Bauholzpilze, Rudolf Müller, Cologne, 2006

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