The function of the joint reinforcement is to control the size and spacing of cracks caused by volume changes in masonry as well as to resist tension. Joint reinforcement is commonly used in concrete masonry to minimize shrinkage cracking. The restriction on wire size ensures adequate performance. The maximum wire size of one-half the joint thickness allows free flow of mortar around joint reinforcement. Thus a 3/16 in. (4.8 mm) diameter wire can be placed in a 3/8 in. (9.5 mm) joint.

On ACI 530-95/ASCE 5-95/TMS 402-95

General Design Requirements

Water penetration through the exterior veneer wythe is expected. The wall system must be designed and constructed to prevent water from entering the building.

The requirements given here and the minimum air space dimensions of Sections 12.8.3, 12.9.4 and 12.10.2 are those required for a drainage wall system. Proper drainage requires weepholes and a clear air space. It may be difficult to keep a 1 in. (25 mm) air space free from mortar bridging. Other options are to provide a wider air space, a vented air space or to use the rain screen principle.