The outer wall is made of brick and faces the outside of the building structure. The interior wall can be built with masonry units such as concrete blocks, structural clay, brick or reinforced concrete. Simply put, a cavity wall is a masonry structure made up of two separate walls (called sheets) that run parallel to each other. These walls are usually referred to as sheets and are joined together with blocks or metal ties.
Between those two walls is a space (usually less than 10 cm or just under 4 inches). Many factors influence how well a masonry cavity can perform each of these functions. Emphasizing one may degrade the performance of another function. A cavity in masonry wall systems is essential for placing masonry units and building the wall.
The other required functions of a cavity are best fulfilled with a clear, predictable air space over the entire height of the cavity, not just 250 mm (10 inches). Many of the materials available for covering rain provide, in a cost-effective manner, good drainage and the required expansion and movement (figure). Drainage mats provide a clear and predictable air space in the masonry with cavities, as well as a thin coating. Especially in the case of uneven stone, a drainage carpet is the only practical way to maintain an air gap with the reality of constructability.
Combined with the right details, these rain protection products eliminate concerns about mortar tightening and result in stronger walls, a lower risk of moisture ingress, better energy performance and a superior appearance.