Everything You Should Know About Dry Rot and How to Prevent It

What is dry rot, exactly? Your wood home is probably one of your greatest investments, so you want to keep it safe. That’s why it’s so important to spot problems, especially ones unique to your home’s structure before they turn into costly damage. Dry rot affects wood and can rot floor and ceiling beams, leading to structural problems, including deteriorated support posts and beams.

Find out if dry rot has affected your home, how to prevent it, and what to do if you discover it.

What Is Dry Rot?

Dry rot (aka brown rot) is wood decay caused by microscopic fungi that feed on wood and consume the cell walls, which give timber its strength. Dry rot leaves dry and brittle wood in its wake and can ruin any wooden structures inside or outside your home. 

Unfortunately, most people cannot identify the signs of dry rot infestation themselves. But if you don’t identify and treat dry rot immediately, it may be necessary to replace all affected timber.

What Causes Dry Rot?

Despite the name, dry rot needs moisture to start. However, it can spread without any source of moisture because it can generate moisture through the digestion of timber. 

Dry rot can happen because the wood wasn’t properly dried before being used or when the wood sits in excess humidity and warm temperatures between 71 to 77 degrees Fahrenheit.

This organism targets cellulose in the wood’s structure and destroys it. The wood later shrinks and turns deep brown. Once rot starts growing, it spreads rapidly. 

Dry rot can travel through various materials, including masonry, and spread throughout a property. If not stopped, dry rot will weaken the whole building to the point of decay.

Identifying Dry Rot

Where to Look for Dry Rot

Look at the areas of your home where there are humidity or water sources.

• Around gutters or downspouts

• Where water runs off the roof along the wall

• On wooden door frames and windowsills

• Near any connections between vertical and horizontal surfaces (i.e., corners)

• On areas with water leaks, such as the roof

• On structural points where wood meets the ground

• By leaky pipes, unventilated attic space, and damp basements or crawl spaces 

Signs of Dry Rot

Several signs indicate the presence of wood rot. If you see any of these signs, you probably have dry rot.

• Visible fungal growth that looks like a fluffy white cobweb

• Strained drywall

• Water droplets on the surface of the wood

• Brown dark timber

• Brittle or weak wood

• A musty or damp smell

• Patches of light purple, orange, or brown that peels easily

• Grayish strands on the wood or timber

• Fruiting mushroom bodies among the spores

Test the area by poking it with a screwdriver. If it penetrates the wood or makes the wood flake easily, there is likely rot. Contact a local home inspector so they can look into this further and check your home for signs of wood rot.

Is Dry Rot Dangerous?

While dry rot spores are not harmful themselves, a house with dry rot isn't a pleasant place to live in, especially with the smell of damp soil filling the air. The damp conditions pose a health hazard for infants, older people, and those with respiratory diseases.

Beyond this, dry rot is very dangerous to your home itself, as it can quickly cause extensive structural damage. 

What Happens If You Don’t Treat Dry Rot?

Dry rot, driven by the fungus Serpula lacrymans, has the power to wreak havoc on your home. Left untreated, it can cause damage to your entire property, as it spreads quickly to any moist wood and even porous masonry. Once present on the wood, it will deteriorate it, impacting the structural integrity of your house. 

In addition, the moisture in your home that allows the dry rot to thrive can cause respiratory problems (especially for those with asthma). A small number of people may find themselves allergic to the fungus that causes dry rot.

The deterioration, and subsequent damage, is progressive and can snowball quickly, so the longer you wait to treat dry rot, the further it will spread and the worse the situation will be. When you have a toothache, it’s best to go to the dentist sooner rather than later to prevent a small problem from becoming a large one. The same rule applies to dry rot.

Can I Treat or Repair Rotted Wood?

Once you identify that dry rot has started, you’ll need to stop it immediately. First, find the source of the problem and eliminate it. A fungicide with borate is one of the most effective ways to kill fungus and prevent dry rot. However, this solution will only work if the dry rot is at the first stages.  For more advanced cases, you will need to replace the affected wood with treated timber.

Because dry rot can move so quickly and cause such damage, you’ll want to get a water damage restoration pro or a local carpenter to evaluate how to treat the dry rot properly. You can also call a local handyperson if they have experience with dry rot.

How to Prevent Dry Rot

When it comes to dry rot, prevention is the key. It’s easier and more cost-effective to prevent decay rather than fix it. The key is to limit wood exposure to moisture in your home with these tips:

• Seal all cracks with caulk. Be sure to scrape away old hardened caulk and replace it with fresh caulk.

• Clean gutters regularly—at least twice a year—to prevent blockages that can lead to water running over the side of your home.

• Make sure to prime any outdoor wood on all sides before painting.

• Check for plumbing leaks and repair any problems ASAP.

• Add a canopy over the entryway to keep the rain away from the doors.

• Use a good dehumidifier in the basement or any house room subject to high humidity.

• Make sure to ventilate bathrooms, attics, crawl spaces, and kitchens properly. 

• Repaint exterior windows and siding if the paint is cracked or peeled.

• Sweep standing water from outdoor decking as soon as the rain stops.

• Check all flashing to ensure water can’t get inside your home.

• Have your house inspected annually to identify any cracks or potential damage.

• Always use decay-resistant or pressure-treated wood for exterior projects. 

• Be proactive and on top of any small issues on the roof and repair them ASAP.