How to Repair and Prevent Dry Rot in Windows

December 19, 2024

Older homes offer lots of character, history, and charm. However, time isn’t always so kind to certain parts of a home, including your windows. Dry rot is a common problem in homes of all ages but can be especially prevalent in older residences with wood window frames and sills.   

Dry rot is more than just an unsightly nuisance. It can make your windows difficult to use and be a threat to your home’s structural integrity. The good news is that you might be able to perform window dry rot repair if the damage isn’t too extensive. In more severe cases, however, replacement windows might be your best option.  

What Causes Dry Rot in Windows?

The term “dry rot” is somewhat misleading. This destructive fungus loves moisture and needs it to thrive. It finds its way into wood and slowly breaks down the wood’s cellulose and lignin (components that give wood its strength). You can think of it as a hungry fungus munching away at your window’s wooden frame over the course of years.  

The fungus behind wood rot (Serpula lacrymans) can stay dormant, lying in wait for years or longer before reactivating when it receives enough moisture.  

Certain conditions help fuel dry rot in windows: 

  • Poor ventilation around windows 
  • Water infiltration from the outdoors 
  • Condensation buildup  
  • High humidity 
  • Poor or degraded sealing and flashing 
  • Water overflow (such as from clogged gutters) 

If you notice any of these conditions around your windows, it’s a good idea to check for signs of dry rot.   

Signs of Dry Rot

Though dry rot can slowly nibble away at your wooden frames, this fungal infestation is good at keeping a low profile. While severe cases of wood rot are easy to see with the naked eye, more moderate instances are easy to overlook. That’s why it’s so important to inspect your windows regularly and look closely for telltale signs of wood rot:   

  • Visual Decay: Look for blistering or peeling paint; warped or sagging wooden surfaces; cracking or shrinking wood; or dark brown discoloration along the wood surface. 
  • Spongy Feel: Press down on your wooden window frames with your fingers or a tool, like a screwdriver. If the wood feels spongy, soft, or brittle, that’s a big red flag. Press your screwdriver into the wood. If it’s able to pierce the wood, you’ve likely got dry rot. 
  • Smell: Fungal growth is associated with a damp, musty odor around your wooden window frames. You may even see a white or gray cotton-like substance around your window frames. That’s the fungus itself.  

If you find any of these signs of dry rot, investigate further. Visible or surface issues are often just the start. The damage could be much more extensive.  

Should You Repair or Replace Dry Rot Windows?

So, you’ve got dry rot around your windows. It’s not a fun club to be a member of, but instead of regretting your luck, it’s time to take action.  

The first important question to answer is whether you can perform window dry rot repair or whether you need to replace your entire window altogether. 

Take some time to fully assess the damage to your window frame. If you notice flaking or bubbling paint in one area, look around the rest of the frame. Use the screwdriver touch test we mentioned above to see if any parts of the frame feel squishy or springy.  

If the damage is minor and only affects a small portion of the window frame, there’s a good chance you can repair the frame.  

Repair isn’t always possible. You’ll likely need to replace your window if: 

  • The dry rot extends deep into the frame or sill. 
  • Multiple areas of the window are affected. 
  • It’s difficult to open or close your window. 
  • You find moisture in the wall cavity around the window. 
  • You see active signs of fungal growth.  

Tips for Window Dry Rot Repair

If you’re making repairs, you’ll want to remove the damaged wood, treat the area with fungicide, and fill the affected area with an epoxy wood filler. You can also splice in new wood as an alternative option. Repairing your window frame is a great way to extend its life while also stopping the fungus from doing any more damage.   

Let’s take a closer look at each step in the process.  

Apply Wood Treatments

Before you begin fixing any of the damage caused by dry rot, you’ve first got to get rid of the fungus so that it doesn’t keep snacking on the rest of your window frame.  

Follow these steps: 

  1. Remove all visibly damaged wood. 
  2. Clean and dry the affected area. 
  3. Apply a fungicide treatment to kill active spores and prevent future growth. 
  4. Give the treatment 24 to 48 hours to dry completely.  
  5. If the wood around the removed damage is a little soft, you may want to apply a wood hardener. This specialized liquid resin is used to strengthen and reinforce your existing wood.  

Use Epoxy Wood Fillers

Once you’ve killed the fungus and helped to reinforce your wood, you can begin your window dry rot repair. Epoxy wood fillers are a popular go-to solution for filling in areas damaged by wood rot. Today’s epoxies are water-resistant and offer good durability. These two-part compounds include resin and hardener. When mixed, they create a rock-hard material that permanently bonds with the existing wood. 

Here’s how to apply the epoxy: 

  1. Make sure the area is completely dry. 
  2. Mix equal parts resin and hardener according to the product’s instructions. 
  3. Apply the epoxy using a putty knife or plastic spreader, filling slightly above the surface to allow for sanding. 
  4. Work the epoxy into all cracks and shape it to match the surrounding contours. 
  5. Allow the epoxy 24 to 48 hours to cure completely. 
  6. Sand the surface smooth. 
  7. Prime and paint the area to match your window trim. 

Partial Window Replacements

An alternative to using epoxy for window dry rot repair is to splice new wood into the damaged area. This method is often used for more moderate or extensive dry rot damage where the window frame can still be saved.  

Here’s how to do it: 

  1. Cut away all the damage until you reach solid wood. 
  2. Cut replacement wood to the exact measurements of the damage. (We recommend using a rot-resistant wood like pressure-treated lumber.) 
  3. Test fit the replacement part before final installation. 
  4. Apply waterproof wood glue to all contact surfaces. 
  5. Install the new wooden piece using screws or nails. 
  6. Countersink all fasteners. 
  7. Fill the screw or nail holes with epoxy filler. 
  8. Sand the area. 
  9. Caulk all joints.  
  10. Prime and paint the new section to match your existing window. 

Maintenance and Prevention

Applying a fungicide to damaged areas of your windows will get rid of an active dry rot infestation, but how can you guarantee that it won’t return with a vengeance?  

While you can’t ever completely protect your window frames, there are things you can do to help prevent a future dry rot return. 

  • Inspect your window frames twice a year, looking for signs of dry rot. 
  • Repair worn caulking around your window frames. 
  • Replace old and damaged weather stripping.  
  • Use bathroom exhaust fans during showers. 
  • Clean your gutters and downspouts to prevent overflow. 
  • Trim vegetation away from windows. 
  • Repaint and reseal wooden window frames every three years. 
  • Apply water-repellent treatments to exposed wood surfaces.  

 Find Professional Window Replacement

Inspecting your window frames regularly will help you find signs of dry rot early so you can perform window dry rot repair. However, it’s not always possible to save your windows. If the damage is too severe, it’s often a better idea to simply replace the entire frame. This is also a good opportunity to upgrade to more energy-efficient windows with modern materials. 

Replacing windows is best handled by a professional team like West Shore Home. Our local technicians can inspect all the windows in your home to look for signs of dry rot. We’ll cut away the damage and install new energy-efficient windows that will look beautiful and help keep your home comfortable. 

Contact us today for a free estimate. 

FAQs

Can windows with dry rot be repaired?

Yes, you can repair window frames and sills damaged by dry rot if the damage is minimal and doesn’t affect too much of the frame or sill. Minor dry rot repairs usually involve removing the damaged wood, treating the area with fungicide, and either filling in the area with epoxy or installing a new piece of wood.  

Will homeowners’ insurance cover window dry rot damage?

Most homeowners’ insurance policies don’t cover dry rot damage. This is often considered a maintenance issue rather than sudden, accidental damage. You can always review your policy or speak with your insurance agent to determine what your policy does and doesn’t cover.  

What’s the difference between dry rot and wet rot?

Dry rot and wet rot are distinct types of fungal decay that affect wood. Dry rot is more destructive and can survive on relatively low levels of moisture. Wet rot needs higher moisture content and is typically only found in wet areas.  

Which types of windows are susceptible to dry rot?

Any wooden window frame or sill can develop dry rot. However, windows exposed to consistent moisture, poor ventilation, or water infiltration are most likely to experience dry rot. Proper installation, regular inspections, and good maintenance can all help prevent dry rot.