Some experts recommend that brick units be placed dry on flashing—such as above shelf angles—rather than setting them in mortar.

If the brick are not set in mortar, what holds the units in place? Won’t they slide out away from the wall?

I usually recommend that brick units be laid on flashing without any mortar. The mortar on the surface of the flashing may interrupt the flow of water out of weep holes. When units are installed on flashing without mortar beneath them, there is no mortar to interrupt the flow of water out of the weep holes and water can flow underneath the brick.

Placing mortar underneath the brick unit does not prevent it from sliding on the flashing. Mortar will not bond well to the flashing and with most flashings, there is no bond between the flashing and the shelf angle or foundation.

Resistance to lateral loads is handled by the wall ties. The first tie is typically positioned four or five courses above the flashing. Although not typically relied on in the design of the wall, there is often sufficient friction to handle lateral wind loads as well.