Preventing Moisture-Related Problems in Residential Wood Framing

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Jeanette Fitzgerald

The Prevalence of Moisture-Related Issues Today
Despite the potential destruction that these moisture-related problems can create, building codes require minimum protection. Today's minimum standard building code requirements specify that only a small amount of lumber used in home construction must be treated against rot fungi, termites, and other wood-ingesting insects. The piece of wood that requires protection is the sill plate in slab construction, which separates the cement slab from the wooden structure built upon it.

New construction techniques are changing the interior environments of many residential homes. Over the past few years homes have become more energy-efficient and air-tight. Less natural air infiltration has caused more moisture to build up inside the houses. This moisture-rich air circulates throughout the house day after day, creating a home-sweet-home environment for mold, rot fungi, and termite infestations.

Today, that lack of required wood framing protection costs the construction industry and homeowners a significant amount of money, time, and headaches to remedy. Current estimates show that replacement materials needed to repair damage caused by rot alone account for nearly 10 percent of the annual wood production in the United States. Homeowners pay $2 billion/year to replace wood damaged by fungal decay and wood ingesting insects. To address a mold problem, the average residential remediation ranges between $50-$100K. Currently, there are over 10,000 mold-related law suits weaving their way through the legal system. "Mold, rot, wood ingesting insects and moisture are some of Florida's biggest building issues that I'm confronted with as a builder," said John Dukovac, President of La Maison Homes in Sarasota, Florida.

The average mold remediation in a residence costs homeowners between $50-100K.

It is also important to note that at the present time there are no accepted federal, state, or local health-based standards for permissible exposure to mold and mildew, but mold has been credited with affecting the health of human beings. Runny noses, itchy eyes, wheezing, and skin rashes resulting from mold allergies have been well documented over the last few years. Recently, too, mold has been attributed with causing infections in people undergoing chemotherapy treatments and in people with severely disabled immune systems. Stachybotrys is the mold usually associated with sick building syndrome and it is being investigated as the cause of hemorrhage in the lungs of infants. While the potential threat of mold on human health and well-being is still being evaluated, it is universally accepted that houses should be kept free of mold.

Moisture and the Construction Process
Moisture-related problems stem from wood that has absorbed too much moisture. Unfortunately, it is impossible to keep wood from being exposed to water during the construction process. Typically, the untreated lumber is manufactured at the mill, shipped to the lumber yard, and then sent directly to the construction site where it can sit for weeks or months as the house is being built. From morning dew and fog to Gulf Coast humidity and May showers, exposure to moisture occurs before, during, and after construction.

Wood arriving to job sites today often already contains more water than wood used years ago. As the demand for wood has continued to grow, the supply of wood from the United States has become much younger, or greener. Greener lumber has a higher moisture content than its slightly more mature sibling. As greener supplies make their way onto job sites and into homes, this wood is even more susceptible to moisture-related problems in the future.

In addition, much more wood on United States construction sites today actually came from Canada, Australia, or Europe. The lumber from these new locations experiences the outdoor elements on the open road or a transoceanic voyage before becoming part of an American home. This wood gets plenty of opportunities to absorb rain, mist, and salty water en route.

Moisture is an undeniable presence in the construction process. The average new 2000 square foot home contains about five tons of moisture that must evaporate from the structure.

 

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Originally published in Architectural Record.
Originally published in November 2007

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