Why Is My Window Frame Rotting From the Inside?

Water from a roof leak or siding failure can travel down inside the wall, soaking the wooden window frame where you cannot see it. A failed sealant around the exterior window flashing allows rain to seep in. This trapped moisture has no way to dry out, creating the perfect environment for wood rot to begin from within the structure.

The leak might be small and intermittent, making it hard to detect until the rot becomes visible. You might notice stains on the interior wall or a musty smell before you see the damaged wood. In climates with wet seasons, this slow, hidden moisture accumulation is a common issue for homeowners.

Look for subtle clues like paint that is blistering, cracking, or peeling around the window, which indicates moisture beneath the surface. A persistent musty odor near the window often signals hidden mold or mildew growth alongside the rot. The wood may feel soft or spongy when you press on it, even if the surface looks intact.

Check for drafts or difficulty opening and closing the window, as warped, rotten frames lose their shape. Visible discoloration or dark stains on the interior trim or drywall are strong indicators. Catching these signs early can prevent more extensive structural damage to the surrounding wall.

• Paint that bubbles, cracks, or peels near the frame.
• A soft, spongy feel when pressing on the wood.
• A persistent musty or earthy smell in the area.
• Visible dark stains or discoloration on the trim.
• Drafts or windows that are hard to open or close.
• Visible mold growth on the interior sill or wall.

Repair involves removing all rotted wood and treating any remaining structural members for mold. The exact repair method depends on the damage's extent, from patching a section to full window frame replacement. A proper fix always includes stopping the original leak and ensuring the new materials are properly sealed and flashed to prevent future water entry. This comprehensive approach is necessary for a lasting solution.

To prevent recurrence, ensure your home's exterior, especially around windows, is well-maintained. Keep gutters clean and downspouts directing water away from your foundation. Use exhaust fans to control indoor humidity, and consider adding storm windows or upgrading to more energy-efficient units to reduce interior condensation.