The fruiting bodies of wood decay fungi vary in size, shape and colour. The type of fungi encountered by building inspectors & pest controllers usually reside in poorly ventilated sub-floors, below wet areas of the home, exterior timbers and in areas that retain water in the soil. The durability and type of timbers are factors along with the temperature and environment. Destruction of affected timbers varies with the symptoms involved
Removal of the moisture source usually alleviates the problem. Fungal decay is attractive to termites and if the problem is not rectified it may well lead to future termite attack.
Wood decay by fungi establishes growth in unsealed, split, exposed timbers and/or timber sections. Timber joints and/or sections that have gaps due to shrinkage or poor joinery and have not had ends properly sealed could have established fungal decay that is not visible, this decay may advance to extensive fungal decay within a short period of time. To minimise further decay it is recommended to seal all gaps with sealant and/or paint as a matter of priority.
Decay fungi can cause severe structural damage to any wood member, even wood species such as redwood and cedar. All that is needed is a source of water in contact with the wood. Decay will occur in untreated wood in direct contact with ground, cement or concrete, or exposed to a source of moisture such as rain seepage, plumbing leaks or condensation. Wood kept dry will never decay!
Brown rot fungi feed on the wood's cellulose, a component of the wood's cell wall, leaving a brown residue of lignin, the substance which holds the cells together. Infested wood may be greatly weakened, even before decay can be seen. Advanced infestations of brown rot are evidenced by wood more brown in colour than normal, tending to crack across the grain. When dried, wood previously infested will turn to powder when crushed. Often, old infestations of brown rot which have dried out are labelled as "dry rot." This is really a deceiving term since wood will not decay when dry.
When white rot attacks wood, it breaks down both the lignin and cellulose causing the wood to lose its colour and appear whiter than normal. Wood affected by white rot normally does not crack across the grain and will only shrink and collapse when severely degraded. Infested wood will gradually lose its strength and become spongy to the touch.
Not Common In Sydney, Australia
Most decay fungi are unable to conduct water very far and can only attack moist wood. However, Poria incrassata, called dry rot or the water-conducting fungus, will decay wood which would not be attacked by typical decay fungi. Poria incrassata infested wood is often mistakenly identified as subterranean termite damage. This type of fungus can transport water for several meters through large root-like structures called rhizomorphs. Once established, it can quickly spread through a building and destroy large areas of flooring and walls in as little as a year or two.
Typically, infestations of Poria incrassata begin in dirt filled porches, damp crawl spaces and basements where wood is in contact with the soil. They also begin in moist concrete or damp bricks. At first, yellowish mycelial fans grow over the surface of joists and sub-floors, or in protected areas. Irregular root-like rhizomorphs may appear on foundations, framing, sub-flooring and other moist areas. the rhizomorphs are dirty white when young but turn brown to black with age. They are typically 6mm to 12mm wide, but can be an 25mm or more in diameter in old infestations. they are often hidden in concrete, masonry or behind wood structures. Fruiting bodies do not always form, but when they do they are found on well rotted wood and are flat, up to 12mm thick, and pale olive-gray with a dirty white/yellow rim when young. With age they become dry and turn brown to black. The under surface is covered with small pores.
When Poria incrassata infested wood dries it usually shrinks and cracks across the such cracks or depressed areas in painted woodwork may be the first evidence of a Poria incrassata infestation. The best tool for discovering a Poria infestation is a moisture meter. If wood has a moisture content above 40% and there is no apparent source of water, you could possibly be confronting Poria incrassata or an infestation of subterranean termites. In either case the wood should be treated as soon as possible.
Moulds and stain fungi are sometimes mistaken for decay, and while they may discolour wood, they cause no structural wood damage. The presence of moulds and stains, however, is a sign that conditions are favourable for decay fungi and a preventative treatment may be necessary. In addition, moulds can increase the capacity of wood to absorb moisture, opening the door to attack by decay fungi.
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Office of Fair Trading (NSW)- Building Inspections - A Home Buyer's Guide PDF Reader
Office of Fair Trading NSW - Home Building Service - Includes Licence Check
Institute of Building Consultants
AEPMA - A Code Of Practice - For Prior To Purchase Timber Pest Inspections - Stephen Koelewyn - participant Drafting Committee
AEPMA - Australian Pest Managers Association I am no longer a member of this Association
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