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Wood Decay
Wood decay is an important issue here in the
Pacific Northwest. It happens because our moist climate feeds
fungi on our roofs, our siding, under our house, and every where else
you can think of. Fungi are filamentous organisms which begin as
microscopic spores that land on the surface of wood, and germinate to
produce strand-like cells called hyphae. Hyphae grow through the wood
and secrete enzymes which degrade and weaken the wood.
The term "dry-rot" is often mistakenly applied
to decay, suggesting that decay occurs in the absence of water. Most
fungi can only decay wood which has free water within the cells which is
when moisture exceeds 30% (by weight). Most wood in buildings range
between 7-13%, and decay is not normally a problem in a well
constructed, properly designed building with adequate ventilation and
maintenance. The most common form of fungi decay in the Northwest,
especially west of the Cascades is brown rot. Brown rot fungi is most
common on softwoods, and at the advanced stages, their damage leaves the
wood as a brown, crumbly mass with numerous cross-breaks perpendicular
to the grain.
Signs of fungal attack in wood are often subtle. Decay is a gradual
process which is divided into three stages: incipient, intermediate and
advanced. No inspection device is capable of detecting incipient decay.
However, clues to invasion may be detected as change in color, lack of
luster or brashy appearance. Most decay can be detected at the
intermediate and advanced stages by careful examination of the
structure. Areas which are most subject to attack include: floors
beneath kitchen and bathrooms, poorly vented crawl spaces, wood-soil
contacts around perimeter of home, decks, wooden steps, railings and any
areas where water is collected.
The simplest method for decay prevention and control is to eliminate any
sources of moisture in the structure such as eliminating slow leaks,
maintaining gutters, controlling ground water and keeping a vapor
barrier over the soil in crawl spaces.
However, when Bugaboo gets the call to remedying a wood rot situation,
we have some nifty solutions.
First have the structural repairs done by
a competent contractor. Then any remaining questionable wood can be
treated with a borate solution. One such product is is  JECTA®
Diffusible Boracide contains 40% disodium
octaborate tetrahydrate formulated in a patented carrier system which
facilitates rapid penetration throughout wood of any moisture content.
JECTA is particularly suited for treatment of wood which is coated with
a water repellent finish or is in ground contact, such as fence posts
and utility poles. JECTA kills infestations and prevents termites,
carpenter ants, wood
destroying beetles and decay fungi.
Packed in a 30-cc syringe, JECTA is adaptable to ACTIVE
INGREDIENT:
40% borate
/ A diffusible Boracide (like boric acid) which is an
effective termiticide,
fungicide,
and other wood
destroying organisms box of 3 syringes $ 35.50 (item no. A-027)
Visit their website at http://www.nisuscorp.com/
.
Identification
There are two main classes of wood rot. In one type, the decayed area has
a brown discoloration and a crumbly appearance. It usually breaks up into
variously-sized cubes, giving rise to the name "brown cubical rot."
Another type of rot results in a white or yellow discoloration, with the decayed
wood being "stringy" or "spongy."
Although many decay fungi may grow for long periods without producing any
external evidence of their presence, others produce "fruiting bodies"
on the surface of decaying wood. Fruiting bodies are usually "crusts"
or shelflike "brackets" which are a few inches or so in diameter. The
fruiting body of Serpula lacrimans, e.g., is a rust-brown, crust-like structure
on the wood surface. It has a waxy appearance, with shallow, net-like folds or
"wrinkles." The fruiting body of Poria incrassata is also crust-like.
It is white to light buff when initially formed, but becomes brown as it ages
and dries out. Small pores can be seen in the crust when it is examined with a
hand lens. Gleophyllum trabeum forms bracket-like fruiting bodies. The upper
surface of the fruiting body is dull gray-brown and smooth. The lower surface
has elongate openings (pores) or split-like openings (gills). These fruiting
bodies produce millions of tiny spores which may, in some cases, serve to spread
the decay fungus to other areas.
Also, surface molds, "mildews," and stain fungi are often found
growing on the surface of damp wood and can be confused with decay fungi.
Although these organisms may discolor the wood, they do not break down wood
fibers and thus do not weaken its structure. However, these organisms indicate
that moisture is present and that decay will likely proceed if a wood-rotting
fungus becomes established in the wood.
Life Cycle & Habits
Decay fungi are living organisms which send
minute threads called "hyphae" through damp wood, taking their food
from the wood as they grow. Gradually, the wood is decomposed and its strength
is lost. Such damage is often inconspicuous until its final stages, and in a few
instances homeowners have suddenly found floors breaking through or doors
falling from their hinges due to wood rot. When previously dry wood is
placed in contact with moist soil, or in a location where it is subject to
condensation (such as unventilated crawl space), it is likely that wood decay
problems will occur. Rain leaks, faulty plumbing and leaky downspouts also are
common sources of moisture. In some instances, water can be transported to the
site of decay through strands or "rhizomorphs" of the decay fungi.
Water-transporting strands may extend for thirty or more feet across brick,
concrete or similar materials. The wood decay fungus, Serpula lacrimans, has
been known to transport water up three stories to an area where decay is
occurring. Poria incrassata is also capable of transporting water long
distances. However, these fungi are exceptions to the rule. Most wood-rotting
fungi must have a direct supply of water at the site of decay. Thus the term
"dry-rot," sometimes applied to decay in wood structures, is
erroneous.
Control Measures Prevention
1.If the decay hazard is high, select the heartwood of decay-resistant
species or use wood properly treated with a good preservative.
Conifers from which decay-resistant lumber is produced include Pacific yew,
juniper, redwood, baldcypress, and western red cedar. Durable hardwood species
include osage orange, black locust, red mulberry, catalpa and black walnut.
2.Build on a well-drained site. Use proper grading to prevent water from seeping
under the house. Install effective drain tile, roof overhang, gutters, and
downspouts. Place no untreated wood within 18 inches of the ground.
3.Provide adequate cross ventilation beneath buildings to eliminate dead air
pockets. Install two square feet of opening for 25 linear feet of wall.
Dense bushes or other plants should not be placed in front of these ventilators.
4.Install a vapor barrier on the soil surface to cause soil moisture to condense
on the barrier and return to the soil rather than condensing on the floor and
above joists. Satisfactory barriers can be made by covering the soil with
asphalt roofing paper or polyethylene sheets.
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