Everything You Should Know About Dry Rot and How to Prevent It
There’s no room at the inn for Serpula lacrymans
Highlights
Dry rot is a form of decay where fungi attack wood and destroy cellulose, leaving wood weak and brittle.
Dry rot needs a moist environment and temps between 71 and 77 degrees.
Regular inspection is key to preventing dry rot.
Spotting dry rot early can help in saving your home.
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 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?
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 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.
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.
Frequently Asked Questions
Dry rot itself is usually not covered by insurance, however, most homeowners insurance policies offer coverage for sudden or accidental water damage, which might be the direct cause of your dry rot. If a pipe bursts and subsequently causes water damage which develops into dry rot, your insurance may cover at least a portion of these repairs. However, any additional dry rot or fungal growth that occurs over a longer period would not be covered.
Most home insurance policies don’t include coverage for floor damage either, so if you live in an area prone to hurricanes or flooding, consider purchasing a flood damage policy.
The fungus that causes dry rot, Serpula lacrymans, spreads quickly when it has the right conditions. To germinate, the fungus needs both moisture (with a humidity level above 30%) and a food source, which is usually wood though it can thrive on other cellulose-based materials.
The cost to fix dry rot depends on the extent of the damage. If the problem is isolated to one small area, you might pay between $400 and $1,000, to dispose of any damaged material, have the area cleaned, and repair the structural framing as needed. The cost to replace a rotted support beam that has been damaged by dry rot is significantly more expensive, with an average price of around $3,250—this is why it’s important to fix any leaks or water damage as soon as they crop up.