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What is Dry Rot?

If your floors creak, sag, or bend under your weight, it isn’t always just because your home is “old.”  

It’s more likely an issue with the floor joists below the wooden floor—the supportive beams found in your crawl space. These important structures are easily damaged by moisture which, over time, causes dry rot. 

Understanding how to identify dry rot and how to prevent it from damaging your home in the future is vital for any homeowner wanting to keep their most important asset safe. By the end of this page, you’ll know the best steps to take to remove and avoid dry rot.

How Does Dry Rot Affect Your Crawl Space?

Despite its name, the fungal infestation called dry rot is actually caused by moisture accumulation in your crawl space. This creates the perfect environment for dry rot to thrive and spread.  

In that respect, dry rot acts a lot like mold, but it doesn’t present itself in the same way. With dry rot, you won’t see green, white, or black fuzzy splotches along the wood. Instead, dry rot feeds on the wood’s interior structure, essentially breaking it down from the inside out. This gives the wood a spongy feel and a crackled, pocked appearance like this: 

Unfortunately, dry rot gets its name because it easily spreads to healthy, dry, wooden structures even when conditions aren’t as wet. This has a serious negative affect on your crawl space and home. 

As wooden structures in your crawl space break down, you’re left dealing with structural issues like creaky floors. Even worse, the air quality in your home gets worse as fungal particles are swept up into your living space through the floor.  

3 Major Signs of Dry Rot

Going into your crawl space can be a messy job, and we don’t recommend going down there due to health hazards like fiberglass insulation or mold growth. 

Thankfully, you don’t actually have to go into your crawl space to identify the signs of dry rot. Many symptoms directly affect your home’s structure. Simply look for problems like: 

  • Sagging floors 
  • High electric bills 
  • Foundation cracks 

All these issues are related to, or stem directly from, dry rot. Let’s dive further into each of these problem signs so you know exactly what to look for.  

1. Sagging Floors

Since dry rot feeds on wood, it’s going to affect floor joists in your crawl space. Floor joists are an important component in keeping your home’s floor properly supported

When floor joists are affected by dry rot, they become spongy, soft, and cracked. This is bad news for your home because floor joists hold up the weight of furniture and moving people in your living space. 

Damaged floor joists will bend under this weight and, in worst-case scenarios, collapse as a result. You can see an example of this in the image. In your home, this translates to sagging floors that dip under your weight. You might also notice leaning furniture or dishes that rattle when you walk past a sink or cabinet.  

2. High Electric Bills

When air in your crawl space becomes humid, it heats up and the gas (water vapor) expands. As a result, the warm air rises through the floors in into your home. When this happens in a building, experts call it the stack effect.  

Without any action, this causes your energy bills to increase.  High energy bills don’t directly cause dry rot, but if your bills are  higher than expected, it’s probably because of moisture – the same thing that causes dry rot. 

3. Foundation Cracks

Crawl spaces rely on more than just wooden supports and columns, most also have perimeter walls made of brick or stone. These foundation walls may become cracked due to shifting soil, especially after rain or snow. When moisture repeatedly drains into the soil near your crawl space, it erodes the ground over time.

Foundation walls rely on sturdy soil for support, so when the ground becomes weak, these walls shift. As a result, cracks in the foundation arise. Again, while foundation cracks themselves don’t cause dry rot, they are caused by moisture. Some of the moisture that causes foundation cracks also seeps into your crawl space. Eventually, untreated moisture in your crawl space is going to cause fungus, so if you notice foundation cracks, dry rot is likely to follow. 

Can You Treat Dry Rot?

Unfortunately, you can’t really “treat” dry rot like mold or other fungi. Once dry rot has taken hold of a wooden structure, the strength and durability of that structure is lost. However, certain techniques like sistering or replacement are one way to deal with rotted wood. Sistering involves placing an identical floor joist next to the damaged one and securing them with a screw or nail.  

That way, the new floor joist helps support the weight of your floor. But because dry rot can spread to other pieces of wood easily, you’ll likely want to completely replace the damaged wood instead.  Keep in mind, these repair options don’t actually stop the underlying cause of dry rot, which is excess moisture in your crawl space. Once damaged wood is replaced, its important to install moisture remediation tools with help from a crawl space specialist. 

How to Prevent Dry Rot

As stated, moisture remediation is necessary to prevent dry rot from growing. Crawl space encapsulation is the most effective way to do this. Encapsulation makes use of different waterproofing tools working in tandem to stop any type of moisture (whether liquid or gaseous) from getting into your crawl space. These tools include: 

When these systems are installed, your crawl space stays fully protected from water. By extension, the conditions needed for dry rot to grow become nonexistent, so wooden structures are protected.

If you decide to invest in crawl space encapsulation, make sure to work with a professional, as DIY encapsulation methods don’t work and often lead to a waste of time, money, and effort.

Dry Rot vs. Mold

You might be wondering, “If dry rot is a fungus, is it similar to mold?”  

They have similarities, but ultimately, they are two different species of fungi. Mold comes in many varieties and each with a slightly different physical appearance.  

Mold may be green, black, white, or yellow. Furthermore, while mold does eat away at organic material like wood, it differs from dry rot because it generally lives on the surface of organic material, eating it from the outside in.  

Dry rot is different in that it refers to one specific species of fungi. Dry rot thrives inside wooden structures rather than on the surface and eats from the inside out.  Moreover, dry rot spreads much quicker than mold which is why it is so detrimental to your crawl space. Neither mold nor dry rot are fun to deal with; generally, the presence of one leads to the other. 

Dry Rot


If dry rot is ignored, your home’s structural integrity becomes compromised. Floors will have a severe sag, furniture may become angled, and your floor could even collapse.  

Yes, dry rot is a specific type of wood rot. There are two types of wood rot – wet rot and dry rot.  

Because a crawl space provides all the conditions needed for dry rot to grow. High humidity, darkness, and wooden structures are all present in an unprotected crawl space. It’s a feeding ground for dry rot. 

Call JES for a Free Estimate!

Since 1993, it has been our goal to provide homeowners with quality service, knowledge, and customer care. When you work with JES, we’ll provide you with a free estimate and crawl space inspection. 

If you are looking for encapsulation services, and you’re looking for a professional team to work with, don’t hesitate to contact us today. We’ll make sure your crawl space stays safe, healthy, and well protected from moisture issues like dry rot for years.

JES serves homeowners across the Tidewater Region and the surrounding areas including: 

  • Charlottesville  
  • Lynchburg  
  • Norfolk  
  • Richmond  
  • Virginia Beach  
  • Hampton 
  • Roanoke 
Phillip Mazzotta

Phillip Mazzotta

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JES Foundation Repair service area map of the Mid-Atlantic region.

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