Q: Should the through wall flashing be installed above or below the limestone or precast concrete over the head of windows?

A: The location depends largely on whether the stone or precast concrete functions as a lintel or is supported by a steel lintel or shelf angle.

If the stone or precast concrete element is a single piece that functions as a lintel to support the masonry above, the flashing should be installed over the lintel. The stone or concrete lintel is a single piece without joints and does not allow water penetration and therefore does not need a flashing below it. Instead, the flashing should be installed directly above the lintel.

The flashing should extend to or beyond the end of the stone or concrete lintel and have end dams. Water penetrating the masonry above the lintel flows out of the wall via weep holes installed along the length of the lintel.

If the stone or precast concrete is merely a decorative element in the wall system and is supported by a steel lintel or shelf angle, the flashing should be installed on the angle supporting the stone or concrete. This flashing should extend to or beyond the ends of the steel lintel and contain end dams or should be continuous when shelf angles are used. The flashing should extend just beyond the exterior face of the masonry wall so that sealant can be installed between the underside of the flashing and the top of the masonry below for the portion of the flashing in the masonry on either side of the window.