Both wet rot and dry rot are caused by fungus feeding on damp wood. But they behave differently and require different treatments. Wet rot needs constant moisture to grow and usually stays confined to the damp area. Dry rot, on the other hand, is far more aggressive—it can travel through masonry, destroy structural beams, and lead to serious foundation issues.

Understanding the difference is the first step toward stopping further damage and preserving your home’s structural integrity.

What Does Wet Rot Mean?

Wet rot is the more common and less aggressive type of wood rot. It usually shows up in damp areas and stays in one spot. You might see it on basement walls after a flood, around crawl space floor joists, or anywhere water has been sitting for a while.

Signs of Wet Rot

• Wood feels soft, squishy, or crumbly
• Dark patches or blackened areas
• Mushrooms or fungus growing on the wood
• A damp, musty smell
• Peeling or cracked paint over the wood
• Floors that feel uneven or saggy

What Causes Wet Rot?

Wet rot happens when wood stays wet for a long time. This often starts when water leaks into your home—maybe from a crack in the foundation, a broken gutter, or a sump pump that stops working. Water can also build up around your foundation if the ground doesn’t drain properly. 

In some homes, water pressure in the soil (called hydrostatic pressure) pushes moisture right through basement walls or floors. Leaky pipes, roof problems, or high humidity in the crawl space can also lead to wet rot.

How Do You Treat Wet Rot?

1. Fix the Source of Moisture: The first and most important step is to stop the water from getting in. This might involve basement waterproofing, installing a sump pump or adding a backup system, sealing your crawl space, or improving exterior drainage so water flows away from the house.
2. Remove and Replace Damaged Wood: Any wood that’s soft, crumbling, or structurally unsound should be taken out and replaced with new, treated lumber that’s resistant to future moisture issues.
3. Treat Surrounding Wood with Fungicide: Even if some areas look unaffected, nearby wood should be treated with a fungicide to stop any hidden rot from continuing to grow.
4. Improve Airflow and Control Humidity: Once repairs are made, it’s important to keep the area dry. Adding ventilation or using a dehumidifier can help reduce humidity and prevent rot from coming back.
   
   

What is Dry Rot?

Dry rot is the more dangerous and destructive type of wood rot. It can spread fast and far, even into dry wood, brick, or concrete. It’s caused by a specific fungus that eats away at the structure of wood and can even grow through masonry, drywall, or across rooms. 

Signs of Dry Rot

• Deep cracks running across the grain of the wood
• Brittle, crumbly, or shrunken wood
• Gray, white, yellow, or lilac-colored fungal growth
• A strong, mushroom-like or musty odor
• Wood that warps or shrinks away from joints
• Signs of rot across different materials (wood, drywall, masonry)

What Causes Dry Rot?

Dry rot starts when wood is exposed to moisture—just like wet rot—but what makes it more dangerous is how it spreads. Once the fungus takes hold, it sends out root-like threads (called mycelium) that can travel across masonry, drywall, and other building materials in search of more wood to feed on.

It often develops after a long-term leak or hidden moisture issue, like water trapped behind a finished basement wall or underneath a floor. Poor crawl space ventilation, roof leaks, foundation cracks, or areas with constant high humidity can also set the stage for dry rot. And in homes with expansive soil or poor drainage, moisture can keep seeping in from the ground and go unnoticed for months—especially if there’s no basement waterproofing or drainage system in place.

How Do You Treat Dry Rot?

1. Eliminate the Moisture Source: The first step is stopping the water intrusion. This prevents the fungus from continuing to grow or spreading further into your home.
2. Remove and Replace All Affected Wood: Dry rot can spread farther than what’s visible. Any compromised wood—floor joists, studs, subflooring, or basement framing—needs to be removed and replaced with rot-resistant, treated lumber.
3. Apply Fungicide to Surrounding Areas: Fungicide should be applied not only to nearby wood but also to any adjacent masonry, drywall, or other surfaces where the fungus may have spread unseen.
4. Reinforce Damaged Structures If Needed: If dry rot has weakened your home’s framing, basement floor, or foundation walls, structural reinforcement may be necessary.
5. Improve Ventilation and Keep the Area Dry: Once everything is treated and repaired, it’s important to reduce humidity and improve airflow to keep dry rot from coming back. This might mean adding ventilation to crawl spaces or using a dehumidifier in problem areas.