I have heard that a ladder-type bed-joint reinforcement should be used when connecting clay masonry to concrete masonry. Can truss-type bed-joint reinforcement be used when both the outer wythe and the inner wythe are the same material? If not, when can truss-type bed-joint reinforcement be used?
I would not recommend using truss-type bed-joint reinforcement in cavity walls, even where both wythes are either concrete masonry or clay masonry. This is because the outer wythe of a masonry wall will experience much greater temperature changes than the inner wythe, due to solar radiation and external temperatures. This difference is even greater in insulated cavity walls. The truss-type reinforcement can restrict movement between wythes and contribute to cracking problems. I do not recommend truss-type bed-joint reinforcement in multiwythe grouted masonry walls either. The diagonal wires of the truss-type bed-joint reinforcement are more likely to collect mortar bridges, which interfere with proper wall grouting. Truss-type bed-joint reinforcement is appropriate in single-wythe concrete masonry walls.