Is it Dry Rot or Wet Rot? How to tell the difference.

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Wood Rot can seem scary and confusing if you don’t know what you’re looking at or how to treat it. It spreads quickly, can quickly deteriorate the structure of your home and invites all sorts of pests and bacteria into your living space. 


Even worse? There are different kinds of wood rot ( wet and dry) and the lingo can seem overwhelming when all you REALLY want is an answer on what you’re looking at and how to treat it. 

The Short Answer:

Wet Rot is typically crumbly and moist. 

Dry Rot is typically in long, split sections. 

The Long Answer:

Both forms of rot are due to fungal growth. However these different species of fungus require very different living environments and thus create very different problems for a home owner. 

Dry wood fracture
Dry wood fracture

Dry Rot:

Dry rot is a misnomer. This type of rot isn’t completely dry nor due to dry conditions. However, it does require considerably less moisture than your traditional wet wood rot. 

Dry rot is formed when a type of wood eating fungus forms. The technical term for this fungus is Serpula Lacrymans. This fungus is considered to be one of the most destructive invaders to wooden constructed buildings ( per Serpula Lacrymans Fundamental Biology and Control Strategies ) and is capable of very aggressive spread relatively quickly. 

Dry Rot fungus (Serpula Lacrymans) feeds exclusively on cellulose found in wood and only requires approximately 20% to 40% moisture levels in order to thrive. This type of fungus sends out very small root-like tendrils, called mycelium, in order to spread and gather nutrients. The bonus presence of materials like brick, plaster and stone allow these mycelial threads to also gather calcium and iron ions – further boosting it’s health and ability to spread. 

To make matters worse, Serpula Lacrymans has two different ways to spread. It can spread as mentioned above, via these root like strands, or it can ‘fruit’ and ‘bloom’. Meaning that with enough nutrients present, it can thrive and produce mushroom ‘fruit’ and them ‘bloom’ via releasing spores. 

As dry rot fungus spreads and pulls the cellulose from the wood, it causes it to split, crack and break in cubical fractures. 

Cubical fractures in oak wood
Cubical fractures in oak wood

It is important to routinely inspect not only the exterior of your home, but also your crawlspace. When performing your own inspections, be sure to look closely around air return vents and near your foundation walls, as Serpula loves concentrated oxygen and cool air. Notice any signs of fungal growth, notably with a yellowish or lilac tint. This type of growth is also typically associated with a very distinct mushroom odor. 

If this type of rot is found in your home, please contact a professional like Wood Rescue Team  as time is certainly of the essence.

Wet Rot Window Sill
Wet Rot Window Sill

Wet Rot:

Wet Rot, while decidedly less invasive than the dry rot fungus Serpula, wet rot fungus can encompass many different species of fungi (Coniophora fungus has approximately 20 family members who want to eat your home, C. Puteana being the most common). These different fungi all agree on one thing: they love and thrive on a moisture content of greater than 50%.

Wet Rot, in some ways may seem less serious due to it’s inability to spread outside it’s moisture rich environment. However, it is silent indicator of a costly water issue in your home. 

This can be from improperly routed or clogged french drains, poorly functioning gutters, ground level crawlspace vents, poorly insulated A.C. ducts or other interior water issues typically found below bathrooms or kitchens.  

When inspecting for this type of rot, it is important to pay close attention for any discoloration in your timbers. A fixed leak inside may eliminate it’s water source, but the fungus will continue to use the moisture in the wood until it has dried and typically will begin to crumble.This can leave your home structurally compromised without you any the wiser. 

Additionally, the fungus may now simply be dormant – needing only it’s moisture source to return in order to make a come back.

It is important to routinely inspect your crawlspace and home exterior for all forms of fungal growth, especially near known water sources (Ex: below wet spaces like laundry rooms, bathrooms and kitchens.) This type of rot will typically present with damp, spongy wood and with a musty and damp odor. 

If this type of rot is found in your home, please contact a professional like Wood Rescue Team as your home could be structurally compromised.

If you would like a professional to stop by to take a look at your home exterior, crawl through your crawlspace to verify the structure and stability of your wood and accurately diagnose any need for repair please call 864-626-3555 for a no obligation estimate. 

-Wood Rescue Team