Q: I’m looking at Detail #2 on Page 15-D-2 of the Dimension Stone Design Manual. It seems to me that the horizontal track mounted to the face of the studs is superfluous. Why can I not simply fasten the stone anchors directly to the studs and eliminate the track?
A: In some cases, yes, it could be eliminated, but in the majority of cases it should be included in the detail.
The horizontal track accomplishes two things. The first is load sharing between the studs. A stud frame is designed to resist uniform lateral loading (principally wind loading, although potentially also seismic). There is actually a wind loading for which we must design in interior environments. If the studs are designed to take uniform load and they are 16” (400 mm) on center, then it is important that EACH stud resists the load from only that 16” (400) mm tributary region. If you anchor the stones directly to the studs and you are only fastening to every other stud, then half of the studs will be carrying all of the load, while the remaining half of the studs carry none of the load. This double-loading on half of the stud quantity would result in loads exceeding their design capacity, and buckling of the studs is likely. Even if you chose to fasten anchors to every stud, in which case you might have 3 or 4 anchors in both the top and bottom beds of the stone, you may still not achieve uniform loading as intermediate anchors often do not assume their designed share of the load. The horizontal track is an effective method of equalizing the loads on the studs.
The second benefit of using the horizontal track is that it provides full lateral position adjustment of the anchors, so that the anchors can be placed at their optimum location on the stone panels, and not just where a stud happens to occur.
Pending the design and rigidity of the studs, you may be able to eliminate the track, however that usually involves over-design of the studs because you are only fastening to some of them. It may also force you to position anchors at less than optimum locations of the stone panel. You will find that the horizontal track is in many cases the most cost effective way to address these issues.