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What is Dry Rot?

There are both similarities and differences regarding dry rot and wood rot. If you have dry rot in your floor joists or in other areas under your home, you may run into similar problems as you would if you had wood rot.

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If you’ve heard about wood rot before, you might not know about how it differs from a seemingly similar but slightly different crawl space and foundation condition called “dry rot.” They can seem very similar on the surface, often leading to confusion.

There are both similarities and differences regarding dry rot and wood rot. If you have dry rot in your floor joists or in other areas under your home, you may run into similar problems as you would if you had wood rot.

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Still, it’s important to understand what dry rot really is if you want to know how to handle it. Here’s what you need to know about dry rot on a wood floor, floor joists or any other places you might find it.

Understanding Dry Rot


The first thing you might want to know is more about what dry rot actually is. The words “dry rot” don’t necessarily mean anything to someone without a lot of knowledge surrounding home repair.

This is a quick briefing on what dry rot is, so you know why it’s important.

A Fungal Infestation

Dry rot is a specific fungal infestation. The fungus most commonly called “dry rot” tends to be Meruliporia incrassate in North America and Serpula lacrymans in the United Kingdom and Northern Europe.

There are many reasons you may end up with wood problems similar to dry rot, but “true dry rot” refers to only certain species of fungi. Because other problems, like wood rot, can have similar problems but different fixes, it’s a good idea to see exactly what type of infestation you’re dealing with.

Because the scientific names of these different infestations can be so difficult to pronounce and remember, it’s likely that you’ll hear the “layman’s terms” instead. Ask the expert inspecting your home what they consider “dry rot” and how they distinguish it from other types of rot.

Significant for Structure and Strength

When dry rot gets into your home, similarly to other problems like wood rot, it seriously impacts the strength of the structure. That’s because it literally eats away at the wood, weakening it substantially over time.

You should treat dry rot with the same amount of importance you would use for any other type of rot in a wooden beam. It has a very significant impact on your home, and it’s important that you handle it as soon as possible.

Don’t assume that just because the dry rot doesn’t “look” serious it isn’t serious. If you’ve started to worry that your home may be at risk by dry rot, talk to an expert. That way, you can know the extent of the damage and know whether you’re handling dry rot. 

Not Actually Dry

It may surprise you to hear that “dry rot” isn’t dry. There are a number of different potential reasons that it came to be called “dry rot,” but regardless of the reason for the name, the fungus actually needs some amount of moisture to grow.

However, especially when opposed to high-moisture problems like mold and mildew, “dry rot” does live up to its name by a small amount. Mold and mildew, for example, require humidity levels nearing 70%-80%, whereas dry rot requires a moisture content in wood of around 20%.

This is a good argument for avoiding excess water in your crawl space or excess moisture in your home. If you keep the moisture content low as a whole, you can make sure dry rot doesn’t even have enough moisture to start growing.

Just understanding what dry rot is doesn’t typically help when it comes to avoiding it in your home. To do that, you need to understand what you should be looking out for. That way, you can recognize when dry rot is happening in your home.

Have you noticed any of these symptoms? If so, it’s probably time to call an expert for an inspection. 

Shrunken or Cracked Wood

Dry rot has a very distinctive method of impacting the wood it’s on. It shrinks and cracks in a cuboidal pattern. This is relatively rare to see in other structural concerns, which means if you see it, you should probably be considering dry rot.

This cracking pattern is typically distinctive with its long lines running up and down the length of the wood, with shorter, more jagged lines running across those. This forms the distinctive cube-shaped cracks across the wood.

If you’re in the crawl space and you start to notice this shrinking or cracking, it’s time to call in the experts. Even if it’s not dry rot, you probably do have some serious structural problems to deal with. 

Decay or Material on Floor Joists or Beams

One easy-to-discover symptom of dry rot only arises if you’ve been dealing with this problem for a while without contacting experts to help you deal with it. Dry rot can grow mushroom-like “skin” when it’s been developing for a long time in less-humid conditions.

It’s common for this “skin” to be silky gray or brown, often tinged with patches of lilac and yellow. Even if you don’t see these obviously mushroom-shaped growths, you may start to notice mycelium, which looks sort of like fuzzy ice.

If you’ve started to notice actual material growing on the wood, you’re definitely dealing with a serious infestation. Dry rot on floor joists needs to be dealt with as early as possible, so if you’re seeing this, contact an expert now. 

Musty, Damp Odor

This is one of the most common ways to tell whether you’re dealing with humidity issues in your crawl space. As the humidity mounts and starts to decay the wood, you’ll start to notice a musty odor through your entire home.

This happens because of the “stack effect.” The air in your crawl space doesn’t just stay there. Because of physics, it rises up through your home, which means you’ll start to smell it in the living spaces in your home.

Any time you notice a different smell in your home, it’s a good idea to do some investigating. If that smell is similar to wet, rotting wood, it’s time to call an expert.

What are your options when it comes to fixing dry rot in a wood floor? Unfortunately, dry rot can be very difficult to deal with, and for the most part, it’s not a DIY fix. If you do have dry rot in your floor joists, you’ll want to contact an expert.

This expert may recommend a variety of fixes. These are some of the most common fixes for dry rot.

Removal and Spliced-In Replacements

It can be extremely difficult to avoid the recurrence of dry rot unless you remove all the decayed wood and remaining spores left behind. In most situations, that means removing the wood infected with dry rot and all wood within about a three-foot radius.

Once the wood has been removed, an expert can then splice in replacements for the wood they just removed. These replacements may have an anti-fungal treatment on them to discourage wood rot in the future.

Obviously, this is an extremely intensive process, and it’s not something you can do on your own. Contact a JES expert for more information regarding how you may be able to fix dry rot and similar problems in your crawl space. 

Fungicide and Sterilization

Once you’ve removed all pieces that could convey dry rot, including pieces outside the immediate area of infestation, it’s common for the next step to be making sure any brickwork and stonework doesn’t carry the fungus.

Even though dry rot typically can’t grow in brickwork or stonework, that doesn’t mean it’s completely safe. You still need to make sure it doesn’t carry over to the new wood. That’s where fungicide and sterilization options come in.

These options can include treatments that can be toxic in large quantities or if someone applies them improperly. That’s why if you have stonework or brickwork in the areas surrounding the dry rot, you need to talk to a JES expert about your best options. 

Additional Antifungal Treatments

It’s also important that you invest in antifungal treatments, typically for the entire crawl space or at least for a very wide radius around the initial dry rot. That’s because antifungal treatments can help keep any lingering spores or other fungal problems at bay.

Antifungal treatments are complicated. Some of them may be able to fix very moderate instances of dry rot without completely replacing the wood, but some of them won’t. Some of them, like sterilization techniques, can also be toxic.

This is definitely a complicated subject, so you should only pursue antifungal treatments if you’re directed to do so by an expert. A free inspection from JES can help you understand your best next move.

Clearly, fixing dry rot in your floor joists is an incredibly difficult thing to do. Therefore, it’s a good idea to try and avoid dry rot instead. If possible, you want to make sure your home stays dry and clean; because dry rot requires a significant amount of moisture, keeping the area dry is your best defense.

How can you do that? These are a few of the ways you can proactively avoid dry rot.

Dry Out the Crawl Space

If you currently have water or high moisture in your crawl space, you need to dry it out. The longer there’s water or very high levels of moisture in your crawl space, the more likely you are to end up with serious problems.

Of course, dry rot isn’t the only serious problem you might run into. You can also end up with mold, mildew and other types of fungal infestations that seriously impact your structural integrity.

Especially if you’re dealing with standing water, it’s a good idea to get a JES expert in to help you with this. Not only can you remove the water, but you can actively dry the area out.

Seal Open Crawl Space Vents

Do you have open crawl space vents? If you do, that’s actually one of the things you should pay attention to and fix as soon as possible.

For a long time, people assumed that they needed to allow open vents in crawl spaces because it would help the area “breathe.” However, it lets in more moisture than it keeps out.

This is exactly why it’s important to seal any crawl space vents you have right now.  

Encapsulate the Crawl Space

This is a full fix that can help you avoid crawl space moisture, especially if you have a dirt crawl space. Dirt crawl spaces put you at huge risk for dry rot in a wood floor, so it’s important that you pursue encapsulation.

With encapsulation, you can avoid that moisture, keeping it on the outside where it belongs. That puts you at a lower risk for not only dry rot but also other types of structural failures.

Crawl space encapsulation can be an essential fix for people who typically have high levels of crawl space moisture. That’s why JES recommends it for a variety of crawl spaces.

Allow JES Experts to Help You with Your Dry Rot Problems

Regardless of your current problems, it’s important to tackle any possibility of dry rot as seriously as you can. Even if you don’t have very serious structural problems you’re currently noticing, you want to catch the crawl space issues before they spiral into something very significant.

Dry rot is a very serious problem, and catching it early can make it easier for you to handle. If you think you might have dry rot in your home, contact a JES crawl space expert to learn more about your options.


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