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moldy rotten wood joist in crawl space

Dry Rot: Is Your Home’s Infrastructure at Risk?

Dry rot affecting your wooden supports is a severe structural problem. Learn more about this issue and how it can be fixed.


Almost 20 billion feet of wood board are destroyed by wood rot in the U.S. each year. This is far more than the amount damaged by wildfires. Needless to say, dry rot is a force of nature that can pose a serious risk to a home’s safety and infrastructure. Many times, dry rot damage is mistaken for termite damage. The treatment options for dry rot and termites are very different so a certain distinction must be made.

moldy rotten wood joist in crawl space

Dry Rot Science

Dry rot is more accurately called “brown rot” because it does, in fact, need moisture to survive. The fungus species Serpula lacrymansis the culprit and its spores can stick around in environments for years until the conditions are just right. It needs a wood moisture content of at least 28-30% to thrive. If given the opportunity, dry rot can pull moisture from wet areas to dry areas and can even grow through mortar, concrete, masonry, and plaster. Often times, dry rot is not detected until the damage has already passed the point of no return.

Cleaning it Out and Repairing the Damage

The first step to eradicating dry rot from your home is to have a professional remove all damaged wood as well as the wood within one meter of the visibly damaged pieces. Any nearby material that could also be housing the fungus spores (paneling, ceilings, linings, etc.) must also be removed.

A wire brush will then be used to remove any loose material from the surfaces of the affected area. The “red brick dust” that results from this is actually fungal spores that have accumulated over time. If the dust is not removed, the spores can plant themselves elsewhere and cause the rot to begin again in new areas.

After brushing, all surfaces are coated with a disinfectant. Then the professionals must rebuild the areas they ripped out earlier. Any beams, joists, or posts will be replaced with brand new, pressure-treated wood or wood that is treated with boric acid.

Dry Rot Prevention

The best way to prevent dry rot from damaging your joists, beams, or posts is to control the moisture levels. This is the easiest and most effective way to prevent both mold and fungus growth as one of their key ingredients is humidity. Removing any standing water, sealing up walls and floors with a thick vapor barrier, and installing a self-draining dehumidifier will do wonders for the area. This process will also create an inhospitable environment for other damaging fungi, mold, termites, carpenter ants, cockroaches, and other household pests.

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