Window Sill Repair Concrete |link| (2027)

Apply a rust converter to exposed rebar; allow 20 minutes for reaction. If more than 20% of the reinforcing bar’s cross-section is lost, install a new short bar using a concrete screw anchor or epoxy-grouted dowel. For non-structural sills with lost edges, formwork is required.

A 1972 apartment building in a freeze-thaw climate (Climate Zone 5) was examined. Forty-eight concrete sills exhibited spalling averaging 2 inches deep. Following the protocol above, 44 sills were repaired without replacement. After 5 years, only 2 sills showed new hairline cracks (4.5% failure rate). The total cost was 32% of full replacement, and no water infiltration was reported behind the window frames. window sill repair concrete