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The Home Depot

Causes of Wood Fungi

Pro Referral > Home Guides > Carpentry > Causes of Wood Fungi
Causes of Wood Fungi

Wood is a primary component in just about every facet of the home. From roofing to floors to outdoor additions, wood provides structure, beauty, and protection from the elements; however, since wood is a material that naturally degrades when exposed to certain conditions, it is in every homeowner's best interest to protect the wood in their houses.


Dry rot, brown rot, and white rot are all forms of wood decay that can be attributed to fungus. While homes in some regions of the U.S. are far more prone to seeing fungal damage, these kinds of issues need only moisture and a certain few kinds of conditions to present themselves before taking hold, making wood fungi a concern for homeowners nationwide. The Ohio State University suggests that nearly 10% of our country's annual wood production is used as replacement materials to repair damage caused by decay. Additional studies suggest that more than $17 billion worth of wood damage is caused by fungi each year!


Thankfully, there are measures homeowners can take to reduce their likelihood of being affected by wood fungi. Here are the three leading causes of residential fungal decay and a few tips on how to protect your home from this destructive and costly foe.

  1. 1.Misplaced Moisture Inside the Home

    When a fungus problem occurs, a combination of replacing the affected wood and eliminating the offending water source is typically the most effective treatment.

    If the Grand Canyon demonstrates anything beyond a shadow of a doubt it is this: A little bit of water can be a very powerful thing when left to its own devices for long periods of time. While a leaky pipe behind a wall might not be powerful enough to carve rock, it can certainly create prime conditions for fungal growth. Wood fungi thrive in moisture-rich environments and are especially likely to grow in temperatures between 77 and 90 degrees Fahrenheit. Since most of us tend to keep the interior of our homes somewhere between these two temperatures, all it takes is a little moisture, the presence of wood, and a couple spores (which can be found all over the place!) to create a perfect habitat for fungal growth.


    Small leaks behind walls and under flooring can definitely be difficult to spot. Taking notice of areas of discoloration and having your home periodically inspected by a professional are two ways of identifying small leaks before they become larger issues. Remember: Attics, basements, and crawlspaces are primary areas where moisture issues go unnoticed, so make sure to give them a visual inspection a few times a year.

  2. 2.Insect Activity

    While insects do not actually cause fungal growth, they can hasten its progress by making wood more susceptible. Most homeowners will take action when they spot a large number of insects in their house, but it is important to make sure that areas where insects--especially termites--have been are repaired to make them less hospitable spots for fungal growth.

  3. 3.Residing in a Moisture-Rich Region of the Country

    In moisture-rich areas like the Northwest, Northeast, and Southeast, wood fungi are more likely to be a cause for concern. Unlike a leaky pipe that can simply be fixed, moisture-laden air and high levels of rainfall are things homeowners simply cannot avoid. Homes in these areas are often designed in a way to limit the chances of fungal activity, but adding extra ventilation in particularly moist areas of the home and using gutters, downspouts, and drainage systems to keep water away from the home's structure can be integral parts of reducing the likelihood of fungal growth.


    When a fungus problem occurs, a combination of replacing the affected wood and eliminating the offending water source is typically the most effective treatment. However, when dealing with non-decaying fungus (fungi that stain wood rather than eat away at it) or very mild cases of decaying fungus, replacement may not be necessary. Surface-staining fungus may sometimes be effectively eliminated by scrubbing the affected area with a half-water half-bleach solution. Milder instances of decaying fungus may be treated using Borate, which is environmentally friendly, but lethal to wood-eating fungi and insects. When fungi find an area they like, they'll continue to return as long as conditions are favorable; so no matter what kind of fungus you're dealing with or how mild the situation is, it is always important to find a way to stop moisture from returning to the area or you'll likely be dealing with the same issue again in the very near future.

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