To Repair Rotted Window Sills Best — How

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.

And so he told himself—and now, he’ll tell you—how to repair rotted window sills without losing the soul of the house. Hendricks took a screwdriver—not a fancy tool, just a flathead with a worn handle—and probed the sill. Good wood sings back a hard, bright resistance. Rot gives way like a rotten apple. He marked the soft zone with a pencil: about eight inches long, two inches deep, reaching into the corner where the sill met the side casing. how to repair rotted window sills

He brushed on an exterior oil-based primer, then two topcoats of satin latex. But the real secret came last: he did not caulk the bottom edge of the sill where it met the brick. Many people make that mistake. Caulk there traps water. Instead, he left a ⅛-inch gap—a “weep path”—so any future moisture could escape. Crucially, he checked beneath

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. Repairable

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.

Then came the satisfying part: the excavation. Using a sharp 1-inch chisel and a mallet, he pared away the rotten wood like a surgeon removing decay. It came out in dark, damp flakes. He kept going until he hit wood that was light in color, firm, and dry—no dark streaks, no softness.