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What Is Wood-Decay Fungus? Identifying Rot Under the Home

Tips from a Crawlspace Industry Expert

We live on a planet made up of splendid things—beautiful mountains, amazing seas and oceans, millions upon millions of living organisms in awesome ecosystems.

Out of all those living organisms, I have devoted most of my professional career to studying and learning how to manage wood-decaying fungus. Wood-decaying fungus is a fungi species that feeds and destroys wood in the forest as well as wood in structures. As professionals, we all have heard about black mold; it is another type of fungi. (Interestingly, all molds are fungus but not all fungi are mold.) Even though black mold is harmful to people and considered a risk to health and home, it is the wood-decay fungus that really is the costliest, as it results in structural damage. If left unchecked, major repairs or even complete rebuilds are not uncommon.

When we conduct home inspections, especially in a crawlspace, it is not hard to find evidence of fungal growth on the substrate of the wood. If the home is new construction or has been treated, the chances are less likely to see this evidence until the home is older. However, in certain conditions, even newer homes can develop fungal growth in a relatively short time span and eventually damage the wood. But, in my experience, it is the older, more established homes where we find the most moisture issues and therefore destructive fungal growth.

A Perfect Environment for Wood-Decay Fungus

Wood-decay fungus is a living organism, and it must have the triangle of life to survive. I’m referring to shelter, water, and food. Inside a crawlspace, these living organisms have everything they need to survive, grow, and develop. The crawlspace environment is dark, protecting the organisms from sunlight that would dry them up and wind that would blow them away. The crawlspace is a moist environment, and the wooden members provide the food source that wood-decay fungus feeds on.

Wood-decay fungus spores are so tiny that most of the time they cannot be seen floating around in the air. These spores are like seeds, and when they come in contact with an organic substrate like wood, they will attach and start to germinate under the right conditions. Early in their development as growing spores on the wood surface, you may see them with a magnifying glass, and eventually later in their development you can see them with the naked eye. These growing spores appear like mushroom caps on the surface of the wood.

Taking Root in Your Home

Just like a plant growing in your garden, the spores will spread roots as they germinate and mature. Then, they will bloom and bear fruit and more spores. Before long, you have what is known as a spore colony. These spore colonies are also known as mycelium fans, the vegetative part of the fungus. Through root systems known as hyphae, they feed off the nutrients within the cells of the wood. As the mycelium fans cover the surface of the wood, the wood becomes more predisposed to retaining higher amounts of moisture, which ultimately helps to break down the cell walls of the wood, and the hyphae transports the nutrients to the growing fungus.

As the fungus colonies grow and the moisture content in a crawlspace rises to serious levels of 20% and higher, the fungus will establish a very sophisticated root system that will spread out to other areas of the house to help support the growing need for food. As the moisture levels continue to rise to 28% and higher, the fungus is actively damaging and depleting the strength of the wood as its need for more food increases.

Common Types of Wood-Decay Fungus

Brown rot and white rot are two of the most common types of wood-decaying fungi. As the names indicate, brown rot has a dark coloration and the white rot has a white coloration. However, there are other types of fungus that resemble these wood-destroying fungi. Even though they look similar, they will not destroy the wood. White pocket rot is one that comes to mind, which resembles the wood-decaying white rot. However, this fungus happens when the tree is alive and dies when the tree is dead and has no damaging effects on the tree.

Crawlspace professionals must be able to distinguish the difference as well as maintain a comprehensive understanding of fungal biology and behavioral aspects. A thorough training program is necessary, as well as strategic treatment protocols that will help you successfully control and eliminate this threat to your client’s structure.

Get Help with Crawlspace Moisture Control

Fortunately for homeowners and industry professionals alike, there are numerous resources available. One such resource is speaking with a company like Your Crawlspace Inc. The team at Your Crawlspace has years of experience with crawlspace moisture control.

But Bennie Marshall and his team aren’t just industry experts. They’ve developed patented products and a system to stop, control, and eliminate moisture inside crawlspaces. They have a full line of tools, training materials, and product accessories that will support you and your business, and they will help you with field training also.

The Your Crawlspace team can be contacted at for more information.

Don Richards ACE, CPI

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