How far apart can the connection bolts for a shelf angle be spaced?
Maximum spacing of anchor bolts always should be determined by a structural engineer. The spacing depends on the size of the angle that is used. The angle must be strong enough to span between the bolts supporting the brick masonry without yielding. And it must be stiff enough so that it doesn't induce significant concentrated loads in the masonry wall. The stronger and stiffer the angle is, the farther apart the bolts may be spaced. The stiffness of the angle usually controls the spacing of the bolts. The Brick Institute of America (BIA) in Technical Note 28B Revised II, "Brick Veneer Steel Stud Panel Walls," recommends two criteria to control the deflection of the shelf angle. First, the total downward deflection of the shelf angle should be less than the spacing of the anchor bolts divided by 600 or a maximum of 3/10 inch. Second, the maximum rotation of the shelf angle should be less than 1/16 inch. This usually is interpreted to mean that the deflection of the horizontal leg of the shelf angle plus the torsional rotation of the shelf angle should be less than 1/16 inch, as shown in the drawings. Shims behind shelf angles should be the same height as the vertical leg of the shelf angle.