Dry rot (also known as brown rot) is one of the most damaging forces on household wood in the world. Approximately 20 billion feet of timber is destroyed by wood rot in the United States each year – far more than is damaged annually by fire!
Replacement wood used to repair damage caused by wood rot accounts for almost 10 percent of the annual wood production in the U.S. alone, and wood rot in general leads to about 17 billion dollars of damage each year in the United States.
What is Dry Rot and Brown Rot?
"Dry Rot" is a term most often used to describe a particular kind of dry, cracking, rotting wood. However, dry rot occurs because of a variety of brown rot species, most notably the "true" dry rot fungus known as Serpula lacrymans. Dry rot originally got its name from the thought that it did not need water to survive, but used a fermentation process to survive. Research has long since been proven that theory untrue, and dry rot is now more appropriately called "brown rot".
Dry rot needs much less moisture than other types of wood-rotting fungi -- a wood moisture content of just 28-30% -- to survive. While there is no official proof on the subject, many contractors have observed that dry rot also will not grow on wood with too much moisture.
Protect Your Home from Dry Rot
The Bad News:
- While dry rot is not the most common type of rot, it can deal serious damage to your home and endure conditions that are too dry for other types of rot to thrive. In fact, up to a 75% loss in the toughness of the wood [PDF] is possible with just a 1% decrease in the wood's weight of the wood.
- Dry rot fungus spores are present in most homes and can survive for several years, waiting for the right conditions to grow.
- Dry rot can pull moisture from moist areas to dry areas. It grows through mortar, concrete, masonry, and behind plaster.
The Good News:
- Despite its name, dry rot needs moisture to produce spores-- at least 28-30% moisture content within the wood with a relative humidity of 95% or higher. Most softwood timbers in dry homes, especially in the upper levels, have a moisture content of 12-15%.
- Dry rot problems in basements and crawl spaces can easily be solved by controlling moisture by sealing and dehumidifying the space.
- Treatment of the wood products such as boric acid is known to eliminate and prevent dry root fungi.
Identifying and Treating Dry Rot or Brown Brown Rot Problems
A common first indication of dry rot in a home is the appearance of a "red brick dust". This is actually an accumulation of fungal spores that are covering the surface, waiting for the proper conditions to start to grow.
An outbreak of dry rot commonly occurs several months after a household water event, such as flooding, bursting washing machine hoses, a failed water heater, or leaking pipes.
Dry rot is also common in vented crawl spaces and basements with groundwater flooding.
Dry rot is often not detected until the damage is already very significant. At this point, the following steps are recommended:
Steps to Dry Rot Cleaning and Repair
1) Remove Damaged Wood
All wood that shows decay or visible fungus should be removed, as well as all wood within one meter of the visible decayed material.
2) Remove Materials Near Damage
Plaster, paneling, linings, and ceilings around the dry rot areas can also contribute to the damage and should also be removed.
3) Wire brush Affected Area
Using a wire brush, loose material is removed from all surfaces within 1.5 meters of the furthest edge of the infestation, including metal, masonry, and pipes. Resulting dust and debris is removed as well.
4) Disinfect Area
A disinfectant is applied to all wood, masonry, and exposed soil in within 1.5 meters from the damage.
Substantially rot-damaged beams, joists, and posts are replaced with pressure-treated wood.
Preventing Dry Rot Problems in Your Basement or Crawl Space
Preventing Dry Rot in a Basement: Remove all standing water sources, then install a plastic vapor barrier on the walls and floors. Install a self-draining dehumidifier powerful enough to dry the area. (At least a 100-liter model)
Preventing Dry Rot in a Crawl Space: Seal off all crawl space vents and door covers. Encapsulate the crawl space with a crawl space liner, then install a self-draining crawl space dehumidifier.
Thrasher can help you eliminate dry rot problems at the source. We can dry your basement or crawl space, eliminate flooding problems, and seal out humidity. This not only eliminates dry rot problems, but also creates an environment that is inhospitable to mold, wet rot, and mildew, while helping to keep out termites, carpenter ants, cockroaches, crickets, and other household pests.
We offer free, no-obligation dry basement and crawl space inspections in our service area. We can answer all your questions and point out the sources of humidity and moisture in your home. Contact us today to learn more.