This detail illustrates a masonry window sill condition. The concrete masonry backing is treated with blocking at the perimeter of the opening, which is wrapped with transition material that engages with the air/moisture/vapor barrier in the field of the wall. This provides continuous resistance to air and moisture. Continuous insulation offers excellent thermal control. The masonry sill is anchored to the brick jamb at the ends; longer sills may require intermediate anchors.

The detail incorporates a vertical brick expansion joint and a vertical control joint at the block backing. A system of flashing and weeps below the sill allows moisture to exit the drainage cavity. The rigid thru-wall flashing material is self-supporting across the cavity. The flashing returns vertically at each end termination to form an end dam. The durable drip edge guards against moisture reentry and may be notched to avoid excessively thick laps.