Wood rot or decay is caused by fungi. The two types of fungi with which inspectors are concerned — decay and sapstain fungi — are plants which lack the ability to produce food using sunlight, as most plants do. Instead, they feed on organic substances found in wood cells, causing varying amounts of damage in the process, depending on the type of fungi.

Log homes have a greater proportion of wood in their structure than conventional homes and can, therefore, suffer a greater amount of damage from the actions of decay fungi.

A number of situations can create conditions which encourage wood decay: poor design of the home or building site; inappropriate exterior finishes; environmental conditions; poor maintenance; and simply a lack of understanding of the causes of decay and how it can be prevented.

Inspectors inspecting log homes should have a basic understanding of the causes and effects of decay, as well as how to recognize decay and the conditions that can encourage its development.