Damage Caused by Wood Decaying Fungi
Wood destroying fungus (fungi, plural) or wood decaying fungi, causes more damage to structures than all the fires, floods, and termites combined! Wood decaying fungus requires four fundamentals to survive which are oxygen, favorable temperatures, water and food. Fungus occurs generally when the moisture content of wood exceeds 20 to 30 percent, coupled with optimal temperatures (32 – 90 F), an adequate supply of oxygen and a suitable source of energy and nutrients.
Fungus is a plant that lack chlorophyll. Unable to manufacture its own food, it feeds off of cells in the wood. The fungus secretes enzymes that break down the wood into usable food. Fungi will significantly reduce the strength of the wood, if the condition continues over a period of time.
Two most commons types:
White Rot Fungi:
White rot breaks down all major wood components (cellulose, hemicelluloses and lignin) more or less simultaneously, and commonly causes rotted wood to feel moist, soft and spongy, or stringy and to appear white bleached. Wood affected by white rot normally does not crack across the grain and will only shrink and collapse when severely degraded. The strength of the infested wood decreases gradually until it becomes spongy to the touch and stringy when broken.
Brown Rot Fungi:
Brown rot primarily decays the cellulose and hemicelluloses in wood, leaving a brown residue of lignin, the substance which holds the cells together. Wood affected by brown rot is usually dry and fragile, readily crumbles into cubes because of longitudinal and transverse cracks (tending to crack across the grain). Infected wood may be greatly weakened, even before external evidence of decay can be seen. Brown rot is generally more serious than white rot. Old infestations of brown rot which have dried out will turn to powder when crushed. They are often labeled as “dry rot”. This common term is deceiving, because dry wood will not rot. Actually, wood kept dry will never decay.
Thus, one reason to have a periodic roof cleaning and a treatment with a Borate solution to preserve the wood.