Fungi Control

Decay of wood doesn't happen mysteriously or without cause. Wood that is recognizably rotten is the product of a sequence of events involving a succession of microorganisms operating under certain conditions. Understanding the conditions under which wood in a building can break down is a first step in interrupting the process of decay and preventing wood deterioration.

Fungi can be a cause of wood deterioration. Not all fungi weaken wood: for example, mold will merely stain it. Staining fungi give wood a “blue stain” that goes deep into the interior of the tree and typically occurs before logs are sawn into lumber. According to the Forest Products Laboratory, unlike decay fungi, staining fungi and mold fungi feed off the wood's free water and its sugars but don't impair the strength of the wood. However, if the wood remains wet for too long, it can be eaten by decay fungi.

Molds are notorious for their contribution to poor air quality and potential impact on human health. Mold spores can grow and thrive where there's moisture, including humid air—which means they can proliferate almost anywhere. They grow on many surfaces, wood included, and usually signal a deficiency in a building's moisture management program.

The MC of wood is the deciding factor in the growth of fungi. Wood with an MC of 19 percent or less is dry enough to virtually eliminate the ability of mold to grow. The risk of mold increases with higher moisture content and relative humidity, particularly when these conditions are sustained for extended periods of time. Relative humidity greater than 80 percent is a cause for concern—even though mold growth can be slow initially, higher humidity levels will accelerate growth. Most fungi grow fastest in the 60-80°F range; at freezing temperatures they either do not grow, or grow slowly.⁷

Termite Control

Insects, mainly termites, carpenter ants and powder post beetles, can cause significant property damage, including (though not limited to) wood-frame structures or wood- or cellulose-based components.

They will also attack fixtures and fittings, furniture, cardboard boxes and books; therefore, even steel and concrete buildings are not immune to invasion. Of the offending insects, subterranean termites cause the most damage, particularly the non-native species known as the Formosan subterranean termite. Though found only in the southern U.S., it is responsible for most of the value loss due to insect damage to U.S. buildings in the south.

Installing termite shields has proven to be an effective means of control. Images courtesy of American Wood Council