Masons on my project are laying the joint reinforcement directly on the masonry units and then covering it with mortar. Shouldn't they first place a thin layer of mortar, then lay the reinforcement and cover it with another layer of mortar?
Not necessarily. The National Concrete Masonry Association (NCMA) says joint reinforcement should be placed in a full bed of mortar and not directly on masonry units (NCMA TEK 64). However, installing joint reinforcement directly on the units is common practice, and experience has shown that it doesn't cause problems. If the reinforcement is properly galvanized and if excessive chlorides aren't present, the galvanizing protects any portions of the reinforcing that may not be encased in mortar. In many cases, placing mortar before placing reinforcing isn't practical. It also adds time between placing mortar and placing the units above, in some cases letting the mortar stiffen before the units above are placed.