Dry Rot vs. Wet Rot: How to Tell the Difference
Spotting the differences in types of wood rot is a challenge
Wet rot tends to be white in color, while dry rot often has rusty colors.
Dry rot makes wood brittle, while wet rot creates soft, spongy wood.
Widespread wood rot requires professional removal.
If you notice signs of wood rot on your property, it’s helpful to know which type you’re dealing with. Two types of wood rot are common—wet rot and dry rot. Being able to compare dry rot versus wet rot and identify the differences is challenging but possible. Learn how to figure out what kind of wood rot you’re seeing, which is helpful in determining how to combat it.
What Are the Differences Between Dry Rot and Wet Rot?
The primary difference between dry rot versus wet rot is the type of damage it causes to wood. Dry rot leaves wood brittle and causes warping, while wet rot creates sponginess and softness in wood.
Spores from fungi cause both types of wood rot. However, another key difference between dry rot and wet rot is that Serpula lacrymans is the only fungus that causes dry rot. Many types of fungi can cause wet rot.
Though the terms are used interchangeably, wood rot and dry rot have different meanings. Wood rot is a broad term that describes various types of fungal decay in wood, while dry rot is a specific type of wood rot caused by the fungus Serpula lacrymans. Dry rot can thrive at a low moisture level and spread rapidly across plaster and even masonry to infect new areas of wood.
| Type of Difference | Wet Rot | Dry Rot |
|---|---|---|
| Early signs | White strands | White strands |
| Later signs | White “mushrooms” | Orange “mushrooms” |
| Common wood damage | Spongy, soft wood | Brittle, warped wood |
| Speed of spread | Slow to moderate | Moderate to aggressive |
| Causes | 30+% moisture content | 20+% moisture content |
| Primary locations | Damp wood | Damp wood |
| Secondary locations | Drywall | Drywall and plaster |
| How to fix | Remove damage | Remove damage |
| How to avoid | Ventilate the area | Ventilate the area |
Dry Rot vs. Wet Rot: Differences in Appearance
At first glance, wet rot and dry rot look very similar. However, it takes a close inspection to notice the differences in appearance.
Color and Size
When the fungal spores for dry rot and wet rot germinate, the initial growth looks similar. Both types of wood rot create whitish strands called hyphae that resemble spider webs. They go across the top of the affected wood.
Eventually, the hyphae morph into mycelia, which resemble mushrooms. At this stage, differences in color and size begin to appear.
Wet rot mycelia resemble off-white mushrooms and are smaller and flatter than dry rot mycelia, which can grow into quite complex, large shapes.
What does dry rot look like in the mycelia phase? Dry rot’s mycelia are often orange or red in color, almost resembling rust on a piece of metal. If the wood is drier as the dry rot mycelia form, they can be off-white or light gray with hints of yellow or purple.
Types of Wood Damage
Even though wet rot causes wood to become soft and spongy and dry rot creates brittleness, both types of wood rot eventually affect the structural integrity of the wood. Both wet rot and dry rot eat away at the wood, creating weakness. If the wood is supporting large amounts of weight, it could collapse because of the damage from the rot, causing a structure to fail.
To eliminate the damage, you should call a local water damage restoration professional who can remove the rotted wood. Dry rot is more difficult to eradicate completely than wet rot, meaning it may reappear without the help of a pro.
Concentration of Moisture
Both dry rot and wet rot need some level of moisture in the wood before the spores can germinate. Dry rot spores need at least 20% moisture concentration in wood to begin growing. Wet rot spores need between 30% and 60% moisture concentration. Without the right moisture level available, the spores won’t start growing.
How do you stop wood rot? With both dry rot and wet rot, the best option is to keep moisture away from the wood. Try to dry the area as much as possible and add ventilation to prevent moisture from returning.
Speed of Growth
Dry rot grows more aggressively than wet rot, meaning it can cause structural damage to wood more quickly. You should call a professional to eliminate both types of wood rot, but you should be more urgent when you notice dry rot.
Even though dry rot is more aggressive, both types of wood rot grow slowly. When the fungal spores reach wood with the right moisture concentration, it can take a week or longer for them to germinate. After germination, it can take a few months to a few years for the rot to begin causing major structural damage to the wood.
Frequently Asked Questions
The spread of wood rot results in a physical breakdown of the wood’s cellulose and lignin, causing it to become spongy or brittle. This can lead to structural damage. Mold and water damage do not damage the physical structure of the wood. When further considering water damage versus mold versus wood rot, all three issues can create a musty or damp odor in the area. All three can also cause discoloration of the wood.
Wood rot is not as dangerous as black mold. When comparing toxic black mold versus wood rot, black mold is a far more dangerous type of fungus for your health. When someone inhales black mold spores, it can cause severe respiratory issues. Although some people have a sensitivity to the spores found with wood rot, the majority of people have no reaction if they inhale wood rot spores.
Pressure-treated wood rot is possible, but the pressure-treatment process reduces the risk of experiencing either dry rot or wet rot. Pressure treatment inhibits the growth of the fungi that cause wood rot. If the pressure-treated wood has constant exposure to moisture, wood rot is eventually possible, just less likely. Screw holes, nail holes, cuts, and nicks in the pressure-treated wood can create a greater risk of exposure to wet rot or dry rot.
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