Q: Shelf angles are usually shimmed during installation to account for variations at the concrete slab edge. Typically, horseshoe shims are used around these bolts. For angles with a 6-inch vertical leg, the bolts attaching the angles to the floor structure are often near the upper portion of the angle. In this case, the horseshoe shims only extend about half the height of the angle.

Is this a problem?

A: Shims must be sized so that they are tall enough to provide support over the full height of the back leg of the steel shelf angle. These shims must extend to the bottom edge of the shelf angle. When the shelf angle is loaded, the bottom should be contacting the shims to provide proper support for the masonry wall.

The angle can rotate if the shim does not extend to the bottom. This rotation can create cracking or even failure of the bolts because the reduced bearing increases the tension load on the bolts.

It is usually necessary to support the masonry, remove three courses of bricks, and reset the angle with proper shims in order to correct walls with improper shimming. New flashing and brick should be installed after the shelf angles are properly secured.