A shelf angle is a structural steel member that supports and transfers the dead load of the brick back to the building frame. Shelf angles can be connected to the building's structural frame in several ways. If the structural frame is steel, the angle can be bolted or welded to the spandrel beam. If the structural frame is concrete, the angle usually is bolted to inserts cast in the concrete spandrel or floor slab. CONSTRUCT EXPANSION JOINTS UNDER THE SHELF ANGLES The leg of the shelf angle should be sized to support the load without deflecting more than 3/10 inch. Differential movement between the brick and the structural frame, such as thermal movements and frame shrinkage, also must be accommodated. Otherwise, the masonry can crack. To prevent this, construct a continuous horizontal expansion joint directly below every shelf angle. DON'T FORGET THE FLASHING Wherever shelf angles occur in cavity walls they interrupt the cavity. The result: water that enters the cavity collects at the shelf angles. To divert this water to the outside of the building, install a continuous flashing membrane over the shelf angle. THE FEWER THE SHELF ANGLES THE BETTER Detailing and installing shelf angles is tedious and troublesome. Consequently, the fewer shelf angles required on a building, the fewer problems that are likely to occur-both in construction and use.