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Decay fungi can cause
severe structural damage to any wood member, even wood species such
as redwood and cedar. Every year they cause at least as much damage
to structures as termites. 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.
Once decay has started in a piece of wood, the rate and extent of
deterioration will depend on conditions such as temperature and moisture
content. Under suitable conditions, most fungi species develop fruiting
bodies of various shapes, colors and sizes, These fruiting bodies
contain enormous numbers of microscopic spores which act like seeds.
If a spore comes in contact with a suitable material such as moist
wood, it can germinate and spread the infestations. Many people exhibit
allergic reactions to fungal spores. |
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Brown & White Rot Fungi
Brown and White Rot 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 Fungi are evidenced by wood
more brown in color than normal, tending to crack across the grain.
When dried, wood previously infested will turn to powder when crushed.
Brown rot fungi primarily attack softwoods such as pines, spruce,
and fir. They require a minimum moisture content of 28-32%. Often,
old infestations of brown rot which have dried out are labeled as
"dry rot." This is really a deceiving term since wood will not decay
when dry.
 When
White Rot Fungi attacks wood, it breaks down both
the lignin and cellulose causing the wood to lose its color 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. Boards can become severly damaged
in 6-12 months, and even faster under moist and hot conditions.
White fungus rot most commonly occurs in hardwood materials but
can be found in exterior columns, steps, porches, and decks, as
well as in doors, windows, and door and window frames. Occassionally,
it occurs in wood trim, rafters, joists, sheathing, siding, sills,
joists, and subflooring.
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Water Conducting Fungi
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 infested wood is often
mistakenly identified as subterranean termite damage. This type
of fungus can transport water for up to 30 feet through large root-like
structures call rhizomorphs. They attack softwoods such as pine,
spruce, and fir.
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 begin in earth-filled porches,
damp crawlspaces, and basements where wood is in contact with the
soil, moist concrete, or damp bricks. At first, yellowish myelial
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, or other moist areas.
 The
rhizomorphs are dirty-white when young, but turn brown to black
with age. They are typically ¼ to ½ inch wide, but can be an inch
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 ½ inch thick, and pale olive-grey 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 infested wood dries it usually shrinks and cracks across
the grain. Such cracks or depressed areas in painted woodwork may
be the first evidence of a Poria 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 source of water, you
are probably confronting Poria incrassata or an infestation of subterranean
termites. In either case, the wood should be treated as soon as
possible.
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Molds and Stains
Molds and stain fungi are sometimes mistaken for decay, and
while they may discolor wood, they cause no structural wood damage.
The presence of molds and stains, however, is a sign that conditions
are favorable for decay fungi and a preventative treatment may be
necessary. In addition, molds can increase the capability of wood
to absorb moisture, opening the door to attack by decay fungi.
 Surface-Staining
Fungi, Midlew and Mold give a fuzzy or powdery appeaarance of
various colors such as black, green, orange, red, yellow, and white.
Molds and mildews can grow within may different kinds of materials
as long as there is sufficient nutritive value, moisture, and warmth
present. Moisture can come from condensation, showers, clothes dryers,
cooking, damp basements or crawlspaces, roof or plumbing leaks,
etc.
 Sap-Staining
or Bluestain Fungi stain the sapwood as they grow through it.
Although these fungi do not structurally weaken wood, the resulting
stain limits where or how this wood can be used. The sapwood is
commonly stained blue, blue-black, gray, or brown, but occasionally
shades of yellow, orange, purple, and red occur. The stain may affect
the entire sapwood or be present in wedge-shaped patches, narrower
towards the heartwood.
Sap-staining fungi most commonly occur in roof trim, siding, sills,
joists, and subflooring. Occasionally they occur in exterior columns,
steps, decks, and porches, roof rafters, joists, sheathing, doors,
windows, and door and window frames, floors, walls, and interior
trim. Their most serious effect on wood is that they greatly increase
the porosity of the colonized wood resulting in greater vulnerablity
to water soaking and subsequent decay fungi. Sapstain that has occured
in logs or unseasoned lumber will remain visible in seasoned wood.
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Treatment & Control of Wood Fungus
It is necessary to determine if the fungus is a wood-decay fungus
or a non-decay fungus. If it is a wood-decay type, recognition of
the type is required as different control measures are necessary.
The critical factor in the development of a wood decay damage problem
is not lack of fungi, but lack of conditions that favor its development.
Moisture control remediation should be implemented. Inside the
structure, proper venting of moisture sources from bathrooms, air
conditioners, driers, and other sources of moisture should be instituted.
Leaky plumbing and drain spouts should always be repaired in addition
to treatment. Wet crawlspaces should be vented and plastic sheeting
installed. Structural wood members that are no longer sound must
be replaced..
Treatment for fungi can include also a combination of spraying
, brushing, and fogging. Other preventative treatments can be suggested
by the inspector.
Elimination of surface molds and decay fungi progresses rapidly
after treatment. Within one week, molds will begin to disappear
and fungi fruiting bodies will begin to dry out. Although the treatment
chemicals have no odor, the decomposition of dead fungi may occasionally
result in a "rotten" smell a few days after treatment. This odor
will only last a few days and can be eliminated with the use of
biological odor control agents.
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(860) 582-9242