How To Repair A Rotted Exterior Window Sill Verified May 2026

A rotted window sill is not just an eyesore; it’s a gateway for water intrusion, bugs, and drafts. The good news is that you usually don’t need to replace the entire window. In most cases, you can repair the sill using epoxy fillers or by cutting out and replacing the rotted section.

A well-repaired epoxy sill can last 10–15 years. But always address the source of the moisture first—otherwise, you’ll be doing this repair again next spring. how to repair a rotted exterior window sill