Cavity wall

Weep holes are placed wherever a cavity is interrupted by a horizontal element, such as door or window lintels, masonry bearing angles, or slabs.

[2] Cavity walls were first used in Greco-Roman buildings, but fell out of use until the 19th century, when they were reintroduced in the United Kingdom,[3] gaining widespread use in the 1920s.

Initially cavity widths were narrow and were primarily implemented to reduce the passage of moisture into the interior of the building.

The water barrier is a water-resistant membrane, either applied to the inner side of the cavity as a film or as a troweled or sprayed liquid.

This construction makes it possible to add a continuous insulation layer between the two wythes and, vertically, through the slabs, which minimizes thermal bridges.

[9] However, industry recommendations, often mandated by building codes, typically require that a cavity wall maintain at least a 1-inch (2.5 cm) drainage space free of masonry elements or insulation.

The Affordable Warmth Objective (HHCRO) provides help for low income and vulnerable households to improve the energy efficiency of their properties and reduce heating bills.

[11] Government led research led to the development of advice on the installation of insulation, the definition of local rain exposure zones, and the creation of British Standard BS 8104 in 1992 that sets out the calculation procedure for assessing exposure of walls to wind driven rain to guide the installation of insulation.

[15] Breathing performance; early cavity wall buildings exchange moisture readily with the indoor and outdoor environment.