Preventing Wood Decay Begins By Controlling Moisture
Wood decay is a concern in moist, humid parts of the United States. Moisture is required for the growth of fungi which cause rot. Fungi are living plants that grow small fibers, called mycelia, through moist wood, getting their food from the wood.
There are two major kinds of fungus that cause wood decay: 1) surface molds, and 2) rot fungi. Decay fungi most common in structures are:
- White rot - gives wood a
white bleached appearance. The strength of the wood decreases gradually
until it becomes spongy to the touch and stringy when broken.
- Brown rot - wood turns brown and is broken into brown cubical pieces with cracks perpendicular to the wood grain. It is the principal cause of building decay in the U.S., and causes rapid loss of strength in infested wood.
Water conducting fungi (Poria)-recognized by papery white-yellow mycelial fans and dirty-white to black root-Iike structures called rhizomorphs that can conduct water up to 25 feet from a moisture source to the wood. Consequently, this fungus can attack wood that other fungi cannot, and can destroy large amounts of wood in one or two years.
Wood in unventilated crawl spaces under houses is subject to a lot of moisture. Condensation of water after evaporation from soil is the most common source of liquid water and subsequent decay problems in homes. The pest management professional can do much to remedy this situation by providing proper ventilation, installing a vapor barrier, and treating the wood.
Proper ventilation in crawl spaces can be obtained by installing one square foot of opening for each 25 lineal feet of wall. These openings should be located so as to provide cross ventilation. The opening should be unobstructed.
Installation of a vapor barrier on the soil surface of unexcavated areas will cause soil moisture to condense on the barrier and return to the soil, rather than condensing on the floor and joists above. Adequate barriers can be made by covering the soil with roofing paper or sheets.
It is very important to point out that the application of fungicides or insecticides to fungi infested wood or soil will not stop wood decay. Only by eliminating the moisture source can wood decay be completely controlled. Therefore, the application of chemicals is of very little importance in fungus control work.
When moisture problems result from poorly constructed or poorly maintained building, these problems have to be corrected before wood decay control can begin. Such problems as faulty roofing, siding, plumbing, etc., usually require the services of other specialists. If the source of moisture is removed and the wood dries out, decay will be stopped.
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