Cavity masonry
Cavity masonry: two masonry leaves separated by a clear cavity of 35-75 mm, tied together with wall ties. Used for thermal, acoustic, and moisture performance.
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Cavity masonry (also called double brick or cavity brick) is a wall system built from two parallel masonry leaves separated by a clear cavity of 35 mm to 75 mm, connected by wall ties at regular centres. Both leaves are structural; this distinguishes cavity masonry from masonry veneer, where only the inner leaf (usually timber or steel frame) carries the structural loads.
The cavity acts as a drainage plane and provides thermal and acoustic performance. The NCC 2022 Housing Provisions require the cavity to be kept clear of mortar droppings (snots) and other obstructions, to drain through weep holes at the base, and to maintain the correct clear width throughout the build. Cavity masonry must comply with AS 3700 or AS 4773 under NCC 2022 Clause H1D5, and the design wind class determines the required wall tie duty.
Also known as: double brick, cavity brick, brick cavity wall.
Category: Masonry.
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Last updated: 2026-05-08. Verified: 2026-05-08.