Saturday, December 30, 2006

Wood Decay

Wood decay is created by microscopic fungi which feeds on the starches and sugars that are in the wood. The fungi slowly destroys the wood cell structure of the log.

There are several types of decay fungi, but the prevailing cause of log damage is from brown rot. The wood appears brown and crumbly and looks unusually dry. Sometimes this rot is called "dry rot".

Wood decay fungi requires four conditions to survive: a warm temperature (about 70 degrees to 100 degrees F), oxygen, wood (food source), and water. Keeping the water away from the log contruction is the most effective means of decay control.

Of course, choosing the proper wood species helps control wood decay too. Wood species such as cedar, cypress, redwood heartwood are naturally resistant to decay and insect attack. The heartwood is that portion of the log that is the central column of wood that runs through the center of the log. The sapwood of the log is that wood that surrounds the heartwood and is less durable in nature. The sapwood is the light colored wood: whereas, the heartwood is the darker portion of the log.

The historic log structures of Europe, United States, and Canada are grand because of the virgin timber of years ago. These virgin timbers had large portions of heartwood, thus these log structures have stood for years. Some good examples are the Lodges of Yellowstone, Glacier, and Yosemite National Parks.

(Grand Canyon Lodge photo curtesy of the National Park Service. Photo by L.S. Harrison)

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