Knowledge

Drainage Cavity

Masonry cavity walls consist of two wythes of masonry separated by an airspace connected by corrosion resistant ties. The internal drainage cavity is designed to intercept any water that penetrates through the exterior wythe. Flashings, weep holes and waterproof membranes are used at the base of the cavity to direct water out of the cavity and prevent water from getting into the building. A 1" minimum clear space is required by code.

Mortar Fins & Droppings

Mortar droppings from the construction process can fill or bridge across drainage cavities, clog weep holes and prevent the escape of water from the cavity. Mortar fins that bridge the cavity, usually at wall ties, can act as conduits for water to the interior wythe. Masonry cavities should be built free of excess mortar that may impede moisture flow or permit water to saturate the backup.

Mortar Deflectors

Mortar deflectors or nets are often used at the base of cavities to catch mortar droppings which would otherwise clog cavities and weeps and prevent escape of water. Many materials are used for this function including netting or mesh of various types that catch the mortar and prevent it from settling at the base of the cavity. Pea gravel is also traditionally used which, being larger than weep tubes, holds the mortar away from the weeps and keeps them clear. This is a less effective method and mesh or net is preferred.