Wet Rot Vs Dry Rot | What’s the Difference?

In Exterior Wood, Tips by Jamie

When it comes to working with rotting wood, it’s a good idea to understand the different types of rot and just what they might mean for your wood. Wet rot and dry rot are very different in the effects that they might have on your wood and could also make a difference on whether or not the wood is salvageable.

The main difference between wet rot and dry rot is that wet rot requires moisture and dry rot does not. While both wet rot and dry rot can be considered fungal decay, dry rot often looks more like fungus when compared to standard wet rot. 

We will dig into the differences between these two types of rot a little bit more throughout this guide.

What is Wet Rot and What Does It Look Like?

wet rot window sill

Wet rot and dry rot can sometimes look pretty similar in appearance but there are some signs that you can look for. Wet rot happens when there is a high moisture content in the wood, leading to the growth of fungi or bacteria.

Since a high moisture content is what feeds this type of rot, your wood is most likely going to feel very soft and spongy to the touch. The moisture might come from something like rain or even a leak. The moisture levels are typically from some external source of moisture.

To identify wet rot, you might be able to tell by the feel. Remember that we mentioned the wood will feel soft and spongy and probably wet as well. It’s possible that you will notice fungus growing on the wood. Most of the time this is black but not always.

You also may notice areas of discoloration on the wood surface or even on any paint. The discoloration could be different shades, including white, brown, or even black. You will most definitely notice signs of water damage on the wood.

What is Dry Rot and What Does It Look Like?

dry rot inside a home causing severe fungi damages

Dry rot is almost exactly the opposite of wet rot. It is still a fungal decay that will take root in your wood. However, dry rot occurs when there is little to no moisture content. Typically, there is about 20% moisture content for dry rot to start out.

While the name is dry rot, it doesn’t’ actually grow dry. It does need some moisture to grow but it requires very little moisture. Sometimes dry rot is brought on just because of high humidity or poor ventilation.

You might be able to pinpoint dry rot, or an environment conducive to dry rot, if you notice condensation on the surface of your windows.

Identifying dry rot is certainly a different process. Most of the time, you will notice cracks in the wood rather than noticing fungus or growth. You might also see whitening layers on the wood from the growth of mycelium.

Wood that is experiencing dry rot might discolor slightly. It could take on a yellow hue but it does not always. You are more likely to notice dry and crumbly wood as a sign of dry rot.

Read our related article: 10 Best Rot Resistant Woods

Wet Rot Vs. Dry Rot – The Difference

Wet rot and dry rot have several differences. The most noteworthy difference between the two is the fact that wet rot requires high levels of moisture while dry rot does not. Both types of rot do require moisture but dry rot can take root with as little as 20% moisture, which means it can happen from humidity alone.

They are started from very different positions and the names sort that out for you a little bit. However, remember that dry rot is not actually dry. It is wet but has far less moisture than wet rot does.

These two types of rot also look and feel different in comparison to each. Wet rot is spongy, soft, and moist. It might have black fungus or it might have other water damage discoloration. Dry rot is going to feel more dry and possibly crumbly. It could have white on it or it could not discolor at all.

Treatment

There are different ways to treat the different types of rot. If your board is completely rotted, you will most likely need to replace it. However, if it appears to be salvageable, you can treat the rot and see if that works to stop the issue.

Keep in mind that treating wet or dry rot will only be helpful if you also fix the problem that led to rotting in the first place.

How Do You Treat Wet Rot?

To treat wet rot, you need to first eliminate the source of moisture causing the rot, as we mentioned above. Once you’ve taken that step, you can work to repair the rot or replace the wood as needed.

If the rot has not completely ruined the wood, you may be able to stop the rotting with the use of bleach or borate. To use either of these, you will need to strip out the rotting parts of the wood still. Once you’ve removed the rot, you can apply the solution and hope that the rotting will spread no further.

However, if the rot is significant, you will be better off simply tearing out the entire piece of rotted material and replacing it. Make sure your new wood is prepped and treated and then take action to prevent water from reaching it.

How Do You Treat Dry Rot?

Most of the time, you should plan to use a specialist to try to treat dry rot (or wet rot for that matter). If dry rot has set in, you will most likely need to replace the wood completely. Dry rot makes wood very fragile so chances are it could crumble or already be crumbling.

Inspect the area to see how extensive the dry rot is. Remove any affected wood and replace it and repair the area. Again, you need to make sure that you make repairs to clean the source of the moisture that caused the rot to begin with.

If you replace the dry rot wood and don’t fix the problem, you’re just going to have the same problem again before long. Be sure to treat all replaced wood to protect it from the elements and also treat surrounding wood with an antifungal treatment as well to keep it safe.

Prevention Tips

There are steps that you can take to be proactive and try to prevent wet or dry rot from occurring. While you might not be able to completely eradicate the possibility, your preventative measures could go a long way to help.

How Do You Prevent Wet Rot?

One of the best ways to prevent wet rot is to just be proactive with the materials. You can make a point to purchase pre-treated materials, particularly if they are going to be used outdoors and exposed to the elements.

The other thing you can do is take action to prevent the wood from getting wet. Things like guttering and drainage can go a long way to help here. If you have a deck or outside wood setup directly exposed, be sure to treat these with waterproof sealant to protect them from wet rot.

How Do You Prevent Dry Rot?

Dry rot usually occurs after the wood has already been damaged by wet rot. The best way to prevent dry rot is to be proactive about preventing wet rot. However, if rot still occurs, you can do a couple of things to try to prevent dry rot from taking place.

You can apply preservatives or treatments to wood that has been affected by moisture. You do have to first dry out the wood, though. Another option is to use a fungicide or a solution that contains borate to stop any rotting in its tracks and prevent it leading to dry rot in the process.

Some experts recommend using an epoxy treatment that can soak into the pores and cracks of the wood to treat the entire structure.

In some cases, the only way to prevent dry rot is to replace the wood in question.

Final Thoughts

Wet rot and dry rot are very different but you can typically be proactive and potentially prevent both types of rot from ever occurring. If you notice wet rot, you should act quickly to prevent dry rot later on.

About the Author

Jamie

Jamie is the founder of The Backyard Pros. When he was 15 years old he started working at a garden centre helping people buy plants, gardening products, and lawn care products. He has real estate experience and he is a home owner. Jamie loves backyard projects, refinishing furniture, and enjoys sharing his knowledge online.