I have heard people recommend that the top edge of a brick below a reveal be chamfered to allow water to drain away quickly. I have seen many buildings where the brick units below the reveal have been unchamfered and there have been no problems. Having special brick units made with a chamfer is often very expensive. Is this practice required?
I prefer providing a chamfered edge on the top of the brick unit below a reveal. When a chamfered edge is used, I typically recommend that it be a 45-degree angle. With a chamfered edge of this magnitude, water is shed very quickly. In addition, the brick unit should be 100% solid to prevent water from flowing into its cores. A reveal made without a chamfered brick creates a ledge that will collect water and allow it to penetrate the masonry. This is a particular problem when using standard brick units immediately below the reveal because the core may be right at the reveal's edge. This would provide easy access for water to penetrate and fill the cores of the units below. There are many buildings that have not had problems despite using brick reveals without chamfered brick. Performance of any masonry wall system depends on exposure, the region where the building is built, the durability of the brick units and the quality of construction. If unchamfered brick reveals are used, keep their depth to a minimum, typically less than 3/4 inch. Providing a vented cavity will help dry out the masonry faster. The masonry above and below the reveal should have proper flashing to minimize and redirect any water that collects near the reveal's level. Make certain that the mortar joints are completely filled and tooled to form a well-compacted joint.