“Cavity” refers to a space, or gap between the cladding and the structure. Cavities have been standard practice between brick veneer and timber framing for many years. This is because it has always been well understood that brick cladding gets wet, so it needs to be kept away from the wooden framing.
At the end of 2004 a new Building Act was enacted, which was part of a whole raft of changes introduced by central government, largely in response to the “leaky building crisis”. The aim was to improve the Building Industry overall. One of the changes made in 2004 ensured that almost all monolithic claddings were installed over a cavity from then on.
This means the structural framing of the house is separated from the cladding, which reduces the chances of water reaching the framing. In houses built after 2004, the cavity is generally constructed with vertical battens (usually but not always timber) which space the cladding out from the framing by about 20mm. The bottom of each wall is then fitted with a perforated strip, intended to prevent vermin entering the cavity and allow air to circulate freely throughout the cavity, as well as allowing any accumulated water to drain away freely. In some systems the top of the wall has additional ventilation to increase the air circulation. Very few older monolithic clad houses have such a cavity, although some do have alternative means for providing at least some drainage and drying, for example rigid backing to solid plaster comprised of diagonal boards with gaps between