NC State Extension

Wood Rot

by James B. “Jim” Kea
Area Extension Forestry Agent – now retired
Thursday, February 9th, 2006

Warm, wet weather makes a lot of things grow faster. One that most people don’t think about until it’s too late is wood rot. Most homeowners are quite familiar with termites and the damage they cause. However, wood rotting fungi are more likely to damage homes than termites.

Fungi can occur in any part of the house that stays moist, and especially in floors, door frames, porches, roof trim, and decks.

To control rot, homeowners must get rid of the moisture and allow the wood to dry. Pressure treated wood should be used where moisture can’t be eliminated, such as on a deck or fence. Spraying wood with preservative chemicals will not control rot when the wood stays moist.

Rot commonly occurs when the crawl space under the house is poorly drained and ventilated. A lot of people don’t realize the importance of the small vents around the house at ground level. They must be open from spring through fall; otherwise, water can condense on the wood joists causing rot. In addition to good ventilation, a plastic sheet places on the soil is a relatively cheap and effective way of keeping moisture in the soil and out of the house. Four milpolyethylene can be used to cover about 70 percent of the soil. Check the plastic after a heavy rain to make sure that water doesn’t drain on top of the plastic. If that happens, you may have to improve drainage around the house. With polyethylene on the soil, you should have at least one vent about every 15 feet around the house. Without the polyethylene, there should be a vent about every 8 feet. The exact spacing depends on the size of the house and the free air space through the vents. Many homeowners are installing automatic vents. These are a convenience because you don’t have to worry about opening and closing the vents. However, regular vents will do just as good a job providing they are opened. Open vents when night temperatures are over 40 degrees.

Keep gutters and downspouts clear, and inspect the house at least once a year for plumbing leaks, and evidence of rot, as well as for termites and other insects.

In a well built and maintained home, rot will not be a problem. Unfortunately, there seems to be an increasing number of homes that have been either poorly built or poorly maintained. Lack of good building sites and the tightening up of houses for energy conservation are adding to the problem. It’s relatively cheap and easy to avoid rot problems if you know what to look for. We have detailed information on how to prevent rot available at the County Extension Office, and there are several teletips on wood rot and its control.


Revised 2/16/2006.

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