Anchors and Supports
Occasionally the terms “anchor” and “support” are confused or misused. This paper is intended to clarify these terms and their meanings.
The term “support” refers to any material or device which holds or supports stone due to gravity loads. Examples of this condition are concrete haunches at grade or floor slab, metal clip angles, metal plates, or other stones.
The term “anchor” or “tie-back” refers to a (usually) metal item—dowel, strap, disk or other shape, which holds stone vertical or plumb, and is required to resist only lateral loads or horizontal loads.
Typically, an anchor or tie-back will be embedded in a slot or other sinkage in the stone. Where such embedded condition exists, the anchors in question must be of stainless steel or other noncorrosive material.
A common detail places a rod or blade at the toe of a gravity support (angle or plate) to prevent the stone from slipping or tilting at its base. Such a rod or blade is, actually and technically, a tie-back or anchor, and should be of stainless steel. The angle to which it is attached need not be stainless, but should be protected against rust. (ILI will comment on that procedure to inquirers.)
Among the few exceptions to these rules are the anchors used as gravity supports in soffit design, and the anchors which resist the shear loads associated with coping stones on the raked angle of a gabled roof. These appliances take the shape of anchors, but are so used that they resist gravity loads for these specialized stone applications.
Another example of the use of anchors as supports is the orientation of expansion bolts or other expanding appliances so that they carry gravity loads. (Please note that ILI recommends extreme caution in the use of expansion bolts as gravity supports. Such usage requires careful engineering analysis of the loads, conditions and safety factors required.)