How to Treat Dry Rot

Co-authored by Ryaan Tuttle

Last Updated: October 20, 2023 References

Dry rot is caused when the fungus Serpula lacrymans infects timber in forests, but can also destroy wood found in people's homes. If you want to avoid costly repairs, catching and treating dry rot early is really important. If you've found dry rot in your home, you may need to remove the rotted wood and fill the timber in with epoxy to prevent the rot from spreading. You can also take steps to prevent dry rot by making sure that timber in your home is dry and that the heating works.

1

Sprinkle boric acid on wood with signs of dry rot.

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You can stop dry rot with boric acid if you catch it early enough. Boric acid is a powerful fungicide and can eradicate the rot-causing fungi as long as they haven't penetrated more than ¹ ⁄ ₄ inch (0.64 cm) into the wood. Sprinkle the boric acid over the rotting portion of your wood or timber and leave it there for 2–3 days. ^{[1]
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- Dry rot typically looks like puffy, white mold growing out of timber or other wooden surfaces. The rot occasionally “blooms” and produces cobweb-like strands that hang from the rotting wood or yellow-colored lumps of fungal growth. In serious cases of dry rot, you may notice that the wood simply crumbles away. ^{[2]
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- Purchase boric acid at a large hardware store or home-improvement store. Many large grocery stores also stock boric acid. Check in the store's cleaning or household-goods aisle.

2

Scrape away rotted wood for a serious case of dry rot.

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Use a trim router to remove the damaged wood. If the dry rot extends deeper than ¹ ⁄ ₄ inch (0.64 cm), boric acid won't have much of an effect. You'll need to scrape away the rotted wood, which will take the rot-causing fungus with it. ^{[3]
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Expert Source

Ryaan Tuttle
Home Improvement Specialist

Expert Interview. 24 September 2021.} Place a bit into the trim router, then plug it in. Hold the router vertically over the timber and turn it on. Move it smoothly back and forth over the rotted area so the router gouges out all of the rotten wood. ^{[4]
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- You can purchase a trim router at a local hardware store. The tool comes with a variety of bits, so select the one best suited to the timber you're trimming.

3

Fill in the wood with an epoxy bonding agent.

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Epoxy dries solid to strengthen the damaged section. Follow the manufacturer's directions and mix together the various chemical components that form the epoxy. When it's reached a thick, putty-like consistency, smear the epoxy into the gouged-out section of wood with a putty knife. ^{[5]
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- Let the epoxy dry overnight for at least 6-8 hours. Keep any curious children or wandering animals away from the epoxy as it dries.

4

Sand the epoxy so it's flush with the rest of the wood.

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Use coarse 80-grit sandpaper from a local hardware store. Once the epoxy has set and dried, slide the sandpaper across the dried epoxy several times until you've smoothed the material down to the same level as the surrounding wood. Work in smooth strokes and apply a consistent amount of pressure as you sand the wood. ^{[6]
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- If the timber or wood is in a part of your home where it'll be seen, you might want to go over the epoxy once more, this time with a 120-grit sandpaper. This will smooth it out further and make it look more finished.

5

Stop any water leaks near timber in your home.

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Any wooden beams or supports near a leak will be susceptible to dry rot. In most homes, leaks occur near water spigots or behind appliances. If you're aware of a leak in your home, turn off the water to the specific pipe that's leaking. ^{[7]
X
Expert Source

Ryaan Tuttle
Home Improvement Specialist

Expert Interview. 24 September 2021.} Then contact a plumber to come to your home and fix the leak as soon as possible. ^{[8]
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- Even if you're not aware of any leaks, it's smart to check through your home on a monthly basis and make sure that pipes tucked away beneath your sink or behind your washing machine aren't leaking.

6

Ventilate areas where a leak has soaked wooden beams or timber.

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Open the windows and doors in the room with the wet timber to encourage airflow. If you have wet wood in your home, it's crucial that you dry it out as fast as possible to prevent dry rot from infecting the wood. ^{[9]
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Expert Source

Ryaan Tuttle
Home Improvement Specialist

Expert Interview. 24 September 2021.} Also set 2–3 large box fans in the room: point 1 directly at the wet wood and place 1 or 2 more blowing air past the wood and towards an open door or window. ^{[10]
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- Purchase box fans at a hardware store or a home-improvement store near you.

7

Check that heating works in all of your rooms.

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In chilly or wet months, moisture can accumulate in rooms that aren't well heated. This leads to dry rot. So, at the beginning of your wet or cold season, check the heater in every room of your house (including the basement!) and make sure it works. If your home is centrally heated, check all of the air vents in your home at least twice per winter to make sure they're blowing out hot air and not obstructed. ^{[11]
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- If you have electrical heaters in your home and 1 isn't working, contact a local electrician. Ask them to pay a visit to your home and repair the malfunctioning heater.

8

Apply a borate preservative to permanently prevent dry rot.

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Treating exposed timber with a borate wood preservative will ensure that it's rot-proof. If you're concerned that timber may get infected with dry rot in the future, your best bet is to coat the exposed ends of the wood with a liquid borate preservative. Dip a small 2 in (5.1 cm) paintbrush into the container of liquid borate. Use short, even strokes to paint a thick layer of the borate preservative onto whatever timber you'd like to treat. ^{[12]
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- Borate—another term used for boric acid—is a powerful fungicide that's sold at most hardware stores.

Expert Q&A

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Question

Do you have to remove dry rot?

Ryaan Tuttle
Home Improvement Specialist
Ryaan Tuttle is a Home Improvement Specialist and the CEO of Best Handyman, Inc. in Boston, Massachusetts. With over 17 years of experience, he specializes in building home service businesses, focusing on creating scalable and efficient brands. With the help of his global team, the companies have achieved over 10+ million in sales and received recognition through magazine features, and enjoy partnerships with wikiHow and Jobber field service software. Boston Magazine and LocalBest.com have named Best Handyman Boston the Best Handyman in Boston. Ryaan holds Construction Supervisor and Home Improvement Contractor Licenses.

Ryaan Tuttle

Home Improvement Specialist

Expert Answer

You should definitely remove and replace dry rot if there's a lot of it in your home. If you only have a little bit, you might not have to worry.

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Question

How do you fix dry rot?

Ryaan Tuttle
Home Improvement Specialist
Ryaan Tuttle is a Home Improvement Specialist and the CEO of Best Handyman, Inc. in Boston, Massachusetts. With over 17 years of experience, he specializes in building home service businesses, focusing on creating scalable and efficient brands. With the help of his global team, the companies have achieved over 10+ million in sales and received recognition through magazine features, and enjoy partnerships with wikiHow and Jobber field service software. Boston Magazine and LocalBest.com have named Best Handyman Boston the Best Handyman in Boston. Ryaan holds Construction Supervisor and Home Improvement Contractor Licenses.

Ryaan Tuttle

Home Improvement Specialist

Expert Answer

Identify the the source of the moisture that's causing your dry rot. Then, seal away or stop this moisture so it can't seep into the wood anymore.

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Things You'll Need

Getting Rid of Dry Rot

Boric acid
Trim router
Epoxy
Putty knife
80-grit sandpaper
120-grit sandpaper

Preventing Dry Rot

Box fans
Borate wood preservative
2 in (5.1 cm) paintbrush

Tips

The name “dry rot” is somewhat misleading because the fungus only affects timber that's very damp.

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Start treating dry rot as soon as you notice it! It can worsen quickly, so waiting as little as a week can allow the fungus to get a strong foothold in wood in your home.

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If you'd rather not purchase a trim router, you could also use a v-shaped wood gouge to scrape out the rotted wood.

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How to Treat Dry Rot

Steps

Sprinkle boric acid on wood with signs of dry rot.

Scrape away rotted wood for a serious case of dry rot.

Fill in the wood with an epoxy bonding agent.

Sand the epoxy so it's flush with the rest of the wood.

Stop any water leaks near timber in your home.

Ventilate areas where a leak has soaked wooden beams or timber.

Check that heating works in all of your rooms.

Apply a borate preservative to permanently prevent dry rot.

Expert Q&A

Things You'll Need

Getting Rid of Dry Rot

Preventing Dry Rot

Tips

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References

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