ILI does not take an adversarial position regarding the use of steel or wood studs as backup material. Both systems can be made sufficiently stiff to support the lateral loads present in most areas. When ILI is asked to comment on such systems used in conjunction with Indiana Limestone, ILI will make the assumption that the system is sufficiently stiff to resist any lateral loading transferred to it from the stone through its anchoring system.
However, both wood and steel stud systems have potential drawbacks beyond lateral load resistance. These must be considered at the design stage.
Steel stud systems are controversial to some extent. Their connections are typically made with self-tapping screws which hold with only one or two threads, depending on the thickness of the stud material. Wall leaks may allow the entrance of sufficient moisture to attack the screw threads and reduce their strength over short periods. ILI recommends the use of bolts and nuts to attach stone anchors to steel studs and RECOMMENDS AGAINST THE USE OF SELF-TAPPING SCREWS FOR ATTACHMENT OF STONE ANCHORS TO STEEL STUDS.
Wood studs can be expected to shrink. Thus, stiff, brittle materials connected to them may be stressed, and masonry joints may fail. As in the case of steel studs, this condition may not be immediately apparent.
ILI's general rule covering both systems is to approve them as backup materials for Indiana Limestone assuming proper engineering assessment of lateral loads and connections to the studs has been done, and assuming that the weight of the stone in gravity is carried by some other system (as, transferred to grade through stone-onstone construction).
In short, ILI does not recommend the practice of allowing wood or steel stud systems to carry gravity loads through attachment by supports to stud flanges or edges (as, continuous angles or clips attached to the stud flange and supporting stone in gravity).
ILI will comment on this subject to inquirers.