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

Marwa Hasan
Written by Marwa Hasan
Updated December 17, 2021
home with screened patio deck
Photo: Ruth P. Peterkin / Adobe Stock

Highlights

  • Dry rot is a decay where fungi attack wood and destroy cellulose, leaving wood weak and brittle.

  • In order for dry rot to start, it needs a moist environment and temperatures between 71 to 77 degrees Fahrenheit.

  • Regular inspection is key to preventing dry rot.

  • Spotting dry rot early can help in saving your home.

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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 and lead to several 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.

What Does Dry Rot Look Like?

It can be hard to identify dry rot, especially in the early stages. Wood rot is often hidden beneath flooring or behind drywall or siding, but if you take a closer look, some signs can start to become visible later in the cycle.

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 

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 flakes 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.

How Dangerous Is Dry Rot for Your Home and Family?

family sitting outside on their wood patio
Photo: Halfpoint / Adobe Stock

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. 

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.

Can I Treat or Repair Rotted Wood?

Once you identify that dry rot has started, you have to stop it.

  • Find and eliminate the source of the problem.

  • 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 pro involved right away. Consult a local carpenter to evaluate how to treat the dry rot properly.

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