A cavity wall in commercial construction in Australia refers to a type of wall construction that consists of two separate walls (or "leaves") with a gap (or "cavity") between them. This design is commonly used for its thermal insulation, moisture control, and sound insulation properties. The cavity can be filled with insulation material or left as an air gap, depending on the specific requirements of the building.

Key Features of Cavity Walls:

1. Two Leaves: Typically, the outer leaf is made of brick or blockwork, while the inner leaf can be made of brick, blockwork, or other materials.
2. Cavity: The gap between the two leaves, which can range from 50mm to 100mm or more, depending on the design requirements.
3. Wall Ties: Metal ties are used to connect the two leaves, ensuring structural stability and preventing the leaves from moving independently.
4. Insulation: The cavity can be filled with insulation material to improve thermal performance.
5. Moisture Control: The cavity helps prevent moisture from penetrating the inner leaf, protecting the interior of the building.

Relevant Australian Standards:

Several Australian Standards govern the design and construction of cavity walls, ensuring they meet safety, durability, and performance criteria. Some of the key standards include:

1. AS 3700 - Masonry Structures: This standard provides guidelines for the design and construction of masonry structures, including cavity walls.
2. AS 4773.1 - Masonry in Small Buildings, Part 1: Design: While primarily focused on small buildings, this standard includes relevant design principles that can be applied to cavity walls in commercial construction.
3. AS 4773.2 - Masonry in Small Buildings, Part 2: Construction: This standard outlines the construction practices for masonry walls, including cavity walls.

Building Code of Australia (BCA) Requirements:

The BCA, part of the National Construction Code (NCC), sets out the minimum requirements for the design and construction of buildings in Australia. For cavity walls, the BCA addresses several key aspects:

1. Structural Adequacy: Cavity walls must be designed to withstand the loads and forces they will encounter, including wind loads, seismic activity, and other structural considerations.
2. Fire Resistance: Cavity walls must meet fire resistance requirements to prevent the spread of fire between compartments and ensure the safety of occupants.
3. Thermal Performance: The BCA sets out requirements for the thermal performance of building elements, including cavity walls. This includes provisions for insulation and energy efficiency.
4. Moisture Management: The BCA includes requirements for moisture control to prevent water ingress and ensure the durability of the building envelope.
5. Sound Insulation: Cavity walls must meet sound insulation requirements to reduce noise transmission between different areas of the building.