Rot in interior window components, such as frames, sills, or casings, is a serious issue that can compromise the structural integrity of your windows and lead to further damage if not addressed promptly. Understanding the causes of window rot and knowing how to fix and prevent it will help maintain your home’s safety, energy efficiency, and aesthetic appeal.

1. Moisture Intrusion

• Leaks from rain, condensation, or poor sealing can lead to wood absorbing water, creating conditions for rot.

2. Poor Ventilation

• High indoor humidity levels can contribute to condensation buildup, especially on older windows.

3. Aging Materials

• Untreated or poorly maintained wood frames and sills are more prone to rot over time.

4. Improper Sealing

• Cracked or missing caulking and weatherstripping can allow water to seep into window components.

5. Pest Damage

• Termites and other pests can weaken wood, making it more susceptible to rot.

6. Paint or Sealant Wear

• Worn or peeling paint exposes wood to moisture, accelerating the decay process.

1. Soft or Spongy Wood

• Press on the frame or sill; if it feels soft or spongy, rot is likely present.

2. Discoloration

• Dark or stained areas around the window may indicate water damage and early-stage rot.

3. Cracking or Splitting

• Rotting wood often shows cracks, splits, or flaking.

4. Peeling Paint

• Paint bubbling or peeling near the window is a common sign of underlying rot.

5. Mold or Mildew Growth

• Visible mold around the window frame or sill often accompanies rot.

6. Drafts or Gaps

• Rot can cause warping, leading to gaps that let in air or water.

1. Assess the Damage

• Inspect the window thoroughly to determine the extent of the rot.

• Check surrounding areas for additional damage, such as mold, moisture stains, or compromised seals.

2. Remove the Rotted Material

• Use a chisel, scraper, or oscillating tool to carefully remove all rotted wood.

• Ensure all soft or decayed material is eliminated to prevent further spread.

3. Treat the Area

• Apply a wood hardener to stabilize any remaining wood and protect it from future rot.

4. Fill the Gaps

• Use an epoxy wood filler to rebuild the damaged areas.

• Apply the filler with a putty knife, shaping it to match the original profile of the window.

• Allow the filler to dry completely, as per the manufacturer’s instructions.

5. Sand and Smooth

• Sand the repaired area to create a smooth surface that blends with the surrounding material.

6. Prime and Paint

• Apply a primer to the repaired area, then paint it with a weather-resistant, mold-resistant paint to seal and protect the surface.

7. Re-Caulk and Seal

• Reapply caulking around the window to prevent future water intrusion.

• Replace or repair weatherstripping for an additional layer of protection.

1. Maintain Seals and Caulking

• Inspect and reapply caulking around windows annually to keep moisture out.

2. Use Weather-Resistant Finishes

• Paint or stain wooden windows with high-quality, weather-resistant products to protect against moisture and UV damage.

3. Control Indoor Humidity

• Use a dehumidifier or exhaust fans to reduce humidity levels and prevent condensation buildup.

4. Fix Leaks Promptly

• Address leaks from roofs, gutters, or plumbing immediately to avoid water damage near windows.

5. Inspect Windows Regularly

• Look for early signs of wear, damage, or moisture intrusion, and address issues promptly.

6. Install Window Flashing

• Ensure proper flashing is installed to redirect water away from windows.

• The rot has spread to structural components, such as wall framing or load-bearing areas.

• Mold is present, requiring specialized remediation.

• Repairs are extensive or involve replacing window frames, sashes, or glass.

• You want to replace the window with a more energy-efficient model.

Rot in interior windows can escalate into significant problems if left unaddressed. Repairing rot promptly and taking preventative measures will extend the life of your windows, protect your home from water damage, and maintain its appearance and energy efficiency.

Pro Tip: After repairs, consider upgrading to composite or vinyl windows for improved durability and resistance to rot in the future.