Airbricks provide perforated openings built into the base and all round the external walls of a domestic building, in order to ventilate the space beneath a suspended timber floor. They are typically made of ceramic, metal or plastic. Without them, there is a strong possibility that lack of ventilation could result in the moisture content of the timber floor reaching a level at which ‘dry rot’ could commence. Airbricks are 215mm wide and are available in heights of 65mm, 140mm and 215mm (in other words, one, two or three courses), and in different colours to tone with surrounding brickwork. Plastic airbricks are purposely designed so they can be interlocked together to form larger units. Horizontal spacing of airbricks around the base of a building is determined by the Building Regulations.
Fig. 188 A selection of airbricks.
Airbricks built into cavity walls must bridge across the cavity and direct the air flow straight under the floor. This is achieved with either a terracotta or plastic telescopic liner of matching width and height being positioned directly behind the airbrick. A plastic telescopic liner has the advantage that it can be adjusted to suit different widths of cavity wall. Liners channel the air straight into the under-floor space rather than displacing it into the cavity.