Dry rot in wood can happen to any home where wood is present, and If caught early, it can be easy to fix. If left unchecked, dry rot can spread quickly and cause large amounts of damage to your home –  even dangerous living conditions.

What Causes of Dry Rot in Wood

Fungus and damp conditions cause dry rot. The important thing to keep in mind, there are millions of fungus spores living around us all the time. When given the right conditions, spores will thrive on the wood in our homes.

There are different types of rot in wood. But all types are caused by a fungus.

Dry Rot is the most common type and fastest spreading.

Damp conditions and temperatures between 65 and 90 Fahrenheit,  fungus can live almost anywhere.

In Dry Rot, the fungus attacks the cellulose in damp wood.  Cellulose is a compound in the wood that gives the wood its tough and rigid structure and is what makes wood such a great material for building houses. Sadly, it’s also delicious for fungus. By snacking on all the cellulose in wood, the wood begins to shrink and turn a deep brown color – giving the wood its “rotten” look. As it further breaks down, the wood shrinks into smaller brittle chunks, that can easily be broken off. Depending on where the rot occurs, this can be very dangerous.

 

How to Prevent Dry Rot in Wood

It’s important to remember – the wood must be damp for fungus to feed on it. Dry wood will not allow the fungus to attach, and make a home.

Dry rot can be a constant and unrelenting enemy if you live in an area with moisture in the air for much of the year, and moderate temperatures. But even in areas with a dry climate, it’s important to check the home for dry rot at least once a year.

Areas of our home are prone to damp conditions.

• Bathrooms
• Basements
• Exterior Doors
• Windows
• Decks
• Roof
• Laundry Room
• Water Heater Storage Area
• Any area of the home with a plumbing fixture

The only way to prevent dry rot is to keep wood dry. Period. Regular inspections of the home, and taking immediate action when dampness or dry rot is located will keep the damage to a minimum.

 

When conducting home inspections, keep the following in mind:

• Check all visible pipes for leaks regularly. If a leak or damp wood around the pipe is noticed, contact your local plumber or trusted handyman immediately.
• Inspect your basement or crawl spaces under the home at least once a year for dampness. Using a bright light, check all wood and look for dark discoloration. If spotted, test the wood for rot by touching the wood with a screwdriver or other hard object. If the wood is easily penetrated, flakes away, or spongy feeling – you have rot. If the wood still spears in good condition, take steps to dry the damp wood with a fan or even a humidifier (in basements).
• Check door frames and window sills/trim for gaps, crumbling edges, spongy feeling wood. Remember dry rot spreads, so if signs are noticed just in corners or small sections, there’s a chance it could spread to the framing hidden in the walls.
• Check exterior siding for chipped or peeling paint. Paint acts as a protective layer over the siding and if chipped away, you could be leaving room for rot to grow. Using a razor blade or another sharp, hard object, lightly press against the siding. If in good condition, the blade will not do damage. If dry rot has started, the blade will insert deep into the siding.
• Inspect your roof for any missing shingles or tiles. Open spaces allow water to penetrate the lower layers and could cause the wood framing to get damp and leave you open for dry rot.

Repairing or Replacing Dry Rot in Wood

Dry rot can either be repaired – removing the small section and applying a wood hardener and filler or replaced.

Repairing dry rot can be done in areas with minor damage, and is often done as a preventative measure when just a few inches of rot is found.  This is appropriate around window sills or ledges, or small sections of the door trim,  to avoid having to replace the entire window or door frame.

How To Repair Dry Rot in Wood

1. Remove the damaged wood, plus an additional 2-3 inches of healthy wood on either side. This will eliminate fungus spores that may have recently spread.
2. Identify the cause of the dampness, and identify how to prevent it from happening again. You may need to call in professional help if the cause is not easily identified.
3. Apply a wood hardener to any exposed wood in the area where you’re removed the rotting wood. This will seal the wood and prevent any further moisture from getting in.
4. Apply the filler. Wood filler can also be purchased at your local hardware store- often in a kit with the wood hardener. The filler will fill in the holes left by the missing wood.
5. Sand down the filler to either a) create a smooth flat surface for attaching new, healthy wood with wood glue, or b) to be flush and match the surrounding wood area, whichever makes the most sense for your project.
6. Prime and paint your work to match the existing area. Good as new!

Replacing dry rot is necessary for larger sections when patching just won’t do.

This is necessary when siding is rotted, more than 50% of a window or door frame is rotted, or the rot expands over areas larger than 1 cubic foot.

When replacing these larger areas of dry rot, you’ll want to cut out and remove all of the rotted wood, plus an additional 2-3 feet of the surrounding area. For larger sections, the rot may have spread further than you think, so removing extra areas is important for getting rid of all the fungus.

Before replacing the wood, take the time to identify the cause of the rot and make the necessary repairs. If the damage was able to get this bad once, it will surely happen again.