Many architects require that brick be cut to conceal the edge of the shelf angle. This is done so that an expansion joint can be provided under the angle without creating a joint greater than 3/8 inch on the exterior. Brick cut in this manner are typically referred to as lipped brick. Such brick often crack a few years after being installed in the building. How can this be avoided? Should these brick be specially formed units, or should they just not be used at all?
Lipped brick spall for many reasons. The most common cause is mortar or other debris left in the joint between the lipped brick and the brick below. This creates a stress concentration that spalls the brick. Whenever possible, avoid lipped brick. The increase in joint thickness is barely perceivable. If lipped brick are used, it is better if they are formed, rather than cut. Cut brick often leave stress concentrations and will crack much faster than formed brick. This will depend on the amount of overcut. Whenever lipped brick are used, a soft joint must be provided which is free of mortar or debris. Through-wall flashing should always project beyond the face of the masonry. Sealant must be installed between the flashing and the brick below.