Should drips be provided in the bed joint reinforcement in cavity walls to prevent water from being transmitted from one wythe to the other?
In a 2-inch cavity, no significant amount of water is likely to be transmitted from one wythe to the other simply by traveling across the wires. Even in a well-built wall, small amounts of mortar droppings can land on these wires, making the drips ineffective anyway. Drips in bed joint reinforcement or ties also will significantly reduce the strength of the tie for both inward and outward loading. In fact, the ACI 530 Code, in section 18.104.22.168, requires reducing the spacing of ties by 50% if they have drips. For these reasons, I see no benefit in using ties or joint reinforcement with drips in cavity walls.