Dry rot (fungus damage) - Description of and prevention tips

Wood Decay Fungi

Brown rot, white rot and soft rot are three classes of fungi that are listed according to the type of decay they cause. Wood decayed by brown rot fungi looks like dry leather and breaks easily into small cubical pieces. The strength of the wood decreases as the growth spreads. Most of the damage to structures is caused by brown rot. Wood decayed by white rot often assumes a bleached appearance, frequently has black lines through it and feels spongy. The strength of wood attacked by white rot decreases gradually with little loss in strength during early stages of decay. If caught soon enough White rot may be treated by spray of a bleach and scraped away. It is important to correct the moisture problem that caused the wet wood in the first place.

Soft rot fungi looks like brown rot but the affected wood softens gradually from the surface inward developing cavities (invisible to the naked eye) within the wood cell walls. Soft rot occurs in situations where wood is wet over a long period of time, such as an earth-to-wood contact.

Some types of decay fungi colonize only when some event such as a roof or plumbing leak brings wood that is below the fiber saturation point into contact with water for an extended period of time. Unfortunately, we cannot always see an event. Other types create root like strands, called ÒrhizomorphsÓ, which can wick water from wet portions of the wood to dry portions. Decay begins when dry wood reaches the fiber saturation point. Under certain conditions, rhizomorphs have been known to travel 25 ft. and break out again. They needed a long term source of moisture; an earth filled porch will do it. If you cut off the moisture, you stop the invasion and keep it from spreading throughout the house.

Four principles of decay prevention

• 1. Build with properly seasoned wood if possible.
• 2. Keep wood dry.
• 3. Break contact of untreated wood and soil.
• 4. Where soil must contact wood, use properly pressure treated lumber. Concrete counts as soil.