dry rot mycelium on old wooden beam that

What Is Dry Rot? The Causes & Early Signs of Dry Rot

If you’re a homeowner, you’ve likely heard of the term dry rot. Dry rot is wood decay that is caused by wood-destroying fungi, which can cause serious damage within your home. The fungus thrives in damp and poorly ventilated environments and can ultimately cause wood to become brittle and weakened. And, as the wood grows weaker, it can pose a serious threat to the integrity of the home. By understanding what causes dry rot and taking steps to prevent it, homeowners can protect their homes and keep them in good condition for years to come. Here, we’ll answer the question “What is dry rot”, as well as explore the early signs of dry rot, and how to treat and prevent it.

What is Dry Rot?

Dry rot is wood decay that is caused by one of several types of fungi. The fungi that are mainly responsible for dry rot in homes are known as Serpula lacrymans and Meruliporia incrassata. These fungi break down the cellulose and hemicellulose in wood, leaving behind a dry, crumbly material that is easily crushed. This can cause significant damage to structures made of wood, such as homes, decks, and roofs.

So, what causes dry rot to occur? Dry rot is caused by a combination of factors, including high humidity, poor ventilation, and water damage. The fungi needs a moisture content of at least 20% to thrive, so areas that are exposed to water or have poor ventilation are at a higher risk of developing dry rot. Homes and roofs are particularly susceptible to this type of rotting because they are often constructed with wood, which can become affected by the fungus.

The Early Signs of Dry Rot

It is important to be aware of the signs of dry rot in order to address the problem as soon as possible and prevent further damage. Here, we’ll go over some of the early signs of dry rot and how to know if you have an issue in your own home.

Discolored or Cracked Wood

You may be wondering, what does dry rot look like and how can you spot it with your own eyes? One of the first signs of dry rot is discoloration of the wood. This can range from a pale yellow to a dark brown color. The wood may also become brittle and easily crumble. In advanced stages, the wood may develop deep cracks and the surface may appear to be covered in a white, powdery substance known as mycelium. These discolorations and textures can be found on exposed wood such as window frames, door frames, and eaves, as well as on wooden structural elements such as floor joists, beams, and rafters.

Musty Smell

Another sign of dry rot is a musty smell. This odor can be present in rooms with dry rot or in areas where there is a lot of moisture, such as basements or bathrooms. This musty smell is caused by the presence of mold and mildew, which can grow as a result of dry rot.

Visible Mushrooms or Fungi

Yet another sign, which may come as a shock to homeowners if discovered, is the presence of mushrooms or fungi growing on or near the affected wood. These fungi are a sure sign that dry rot is present, as they feed on the cellulose and hemicellulose in the wood.

Weak or Soft Wood

If dry rot is present in your home, you may also notice that the affected wood is softer or weaker than surrounding wood. This can cause sagging or bowing of wooden structures, such as floors or ceilings. This weakness can be dangerous, as it can cause structural failure and collapse.

Additionally, the wood rotting can also cause problems with doors and windows. The frames may become loose or difficult to open and close. This is caused by the weakening of the wood, which can no longer support the weight of the doors and windows. Because of this, it is important to identify the signs of dry rot to protect your home from dangerous (and costly) damage.

How to Stop Wood Rotting

So, how can you prevent dry rot from affecting your home? Luckily, there are some preventative measures that you can take as a homeowner. By taking these steps, homeowners and building managers can help to protect their properties from the damaging effects of fungus.

Keep Wood Dry

The first step in preventing wood rot is to keep the wood dry. This can be achieved by ensuring that gutters and downspouts are in good condition and directing water away from the building, sealing any cracks or openings in the structure to prevent water infiltration, and using a moisture barrier or sealant on the wood. It is also important to keep the wood well-ventilated to prevent moisture from building up.

Use Wood Resistant to Dry Rot

Another important preventative measure is to use wood that is resistant to rot. This includes wood species such as cedar, redwood, and pressure-treated pine. These woods have natural chemicals that make them resistant to rot and decay.

Get Regular Inspections

Regular inspections can also help to catch any early signs of dry rot before it gets worse, allowing for prompt treatment. If dry rot is found, it is important to address the problem as soon as possible. This may involve removing and replacing affected wood, as well as addressing the underlying moisture problem to prevent further spread of the fungus.

Practice Proper Maintenance

Finally, proper maintenance of the wood structures is crucial. This includes cleaning, staining, and sealing the wood to protect it from the elements. It is also important to repair any damage to the wood as soon as it occurs to prevent further deterioration.

How to Treat Dry Rot

If dry rot is found, it is important to address the problem as soon as possible. By knowing how to treat rotten wood, you can be prepared to tackle the problem quickly and efficiently, preventing further damage.

The first step in treating dry rot is to locate and repair any sources of moisture. This can include fixing leaks (including roof leaks), addressing poor drainage, and ensuring that gutters and downspouts are in good condition. Proper ventilation (particularly roof ventilation) is also important to prevent moisture from building up.

Next, it’s crucial to remove any affected wood. This may involve cutting out and replacing sections of the wood, such as floor joists or framing. It is important to remove all of the affected wood to prevent the fungus from spreading to other areas. In some cases, it may also be necessary to remove insulation or other building materials that have been contaminated with the fungus.

Once the affected wood has been removed, it’s important to clean and disinfect the area. This can be done using a fungicide or a solution of bleach and water. When considering how to treat dry rot, this step is important in ensuring that nothing is left behind.

If the dry rot has caused structural damage, it may be necessary to hire a professional to repair or reinforce the structure. This can include installing new joists or beams, as well as reinforcing existing ones. A professional can also ensure that the proper steps are taken to prevent future issues, such as installing any necessary gutters and addressing ventilation concerns. By contacting a professional, you can be confident that your dry rot is not only repaired, but that future dry rot is being prevented.


Dry rot can be a serious problem for homeowners, leading to dangerous and costly damage. However, with proper maintenance and prompt treatment, it can be prevented or at least minimized. By keeping your home dry and well-ventilated, inspecting for early signs of dry rot regularly, and addressing any problems right away, homeowners can help to protect their properties from the damaging effects of rotting wood.

Do you have dry rot in your roof? Or, do you have dry rot that has resulted from poor roof ventilation or inadequate gutter drainage? Contact a quality roofing contractor at Ranch Roofing today to start the process of addressing your home’s needs. Our expert roofing professionals are here to provide you with everything you need, from professional roofing ventilation to minimize moisture, to expert roof repairs and other roofing services.