How To Repair Rotted Window Sills ((exclusive)) May 2026

Then he mixed the two-part epoxy filler. It smelled like a chemistry lab and felt like warm taffy. He pressed it into the cavity with a putty knife, overfilling slightly, mounding it above the original surface. He let it cure for a full 24 hours. Patience, he reminded himself. Rot took years. Epoxy takes a day. Now came the art. The cured epoxy was harder than the original oak. Hendricks pulled out a block plane and a rasp. He shaved the epoxy down to the level of the old sill, then used the rasp to carve the subtle front slope—the “drip edge”—that shed water away from the glass.

If the rot extends into the jack studs or the rough sill below, stop. Call a carpenter. But if it’s just the visible sill and the first inch of substructure, you’re in business. Chapter Two: The Excavation He donned safety glasses—a lesson learned from a flying splinter in ’82—and went to work. how to repair rotted window sills

By the time he noticed the problem, it wasn’t a drip anymore. It was a soft, crumbly patch of wood near the outer edge—dark brown, spongy to the touch, and flecked with the fine orange dust of dry rot. Then he mixed the two-part epoxy filler

Crucially, he checked beneath. Rot that goes all the way through the sill’s thickness and into the wall framing is a different beast. This was surface rot—deep, but not structural. Repairable. He let it cure for a full 24 hours

The repair had cost him $47 in materials and two afternoons of his time. The window would outlast him now—and that, he thought, was the point. Not to cheat death or decay, but to meet it with skill, and to leave behind something still standing.