How To Repair Rotted Window Sills |link| May 2026

“The whole window’s shot,” said the young contractor, tapping it with a hammer. “Needs full replacement. Twelve thousand dollars.”

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. how to repair rotted window sills

Shape the repair to shed water. The sill must slope away from the house, about 5 degrees. Any backward tilt is a suicide pact. Chapter Five: The Armor Hendricks sanded the whole sill smooth—old wood and new epoxy together—with 120-grit, then 220. Dust flew. The patch became indistinguishable from the original under a coat of primer. “The whole window’s shot,” said the young contractor,

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. The window would outlast him now—and that, he

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.

Old man Hendricks had lived in the gable-ended cottage for forty-seven years. He’d painted the clapboards, rehung the shutters, and swept the chimney every autumn. But there was one thing he’d ignored: the slow, silent drip from a cracked glazing bead on the east bedroom window. Every rainstorm, a teaspoon of water would sneak past the paint, lodge itself in the end grain of the sill, and begin its quiet work.

He brushed the hardener into every pore of the cavity. It soaked in, sizzling faintly as it bonded with the remaining cellulose. After an hour, the soft edges turned rock-hard.