Masonry Wall Construction Requirements Under AS 3700

What This Requirement Covers

This requirement summarises the key construction, design and performance obligations for masonry walls in Australia as set out in AS 3700 (Masonry structures and retaining walls) and how those requirements interface with the National Construction Code (NCC) / Building Code of Australia (BCA) and the ABCB Housing Provisions. It explains why masonry-specific rules exist - to ensure structural adequacy, durability, fire resistance and resistance to wind and earthquake actions for walls built from fired clay, concrete masonry and calcium-silicate units - and who must follow them (designers, certifiers, builders and owners of Class 1 to 10 buildings where masonry is used). The requirements address unit and mortar selection, wall dimensions and tolerances, ties and reinforcement, footing and support conditions, exposure and durability, and how masonry achieves required fire-resistance levels.

AS 3700 works alongside the NCC. For Class 1 and 10 buildings the ABCB Housing Provisions and NCC Volume Two reference and modify AS 3700 in specific situations (for example limits on wind class, soil class and unit strengths). For other building classes AS 3700 is referenced in NCC Volume One as an acceptable solution for masonry design and construction. Compliance therefore requires satisfying the numerical and detailing rules in AS 3700 plus any applicable NCC clause, ABCB Housing Provision or state schedule variation.

Key Requirements

1. Design standard: Masonry walls must be designed and constructed in accordance with AS 3700 (most recent edition as adopted by the NCC) for structural, durability and detailing requirements; for concrete elements see AS 3600 where referenced by NCC, and for timber framing interfaces see AS 1684 where relevant.
2. Applicable building classes: AS 3700 applies to masonry used in buildings across Classes 1 to 9 where the NCC or project documentation requires design to this Standard. NCC Volume One references AS 3700 for masonry structures; NCC Volume Two and the ABCB Housing Provisions specifically reference AS 3700 for Class 1 and 10 buildings in many permitted situations (see NCC Volume Two, Part references and ABCB Housing Provisions Part 5 sections).
3. Unit compressive strength: Where the ABCB Housing Provisions apply to Class 1 buildings, masonry unit minimum compressive strengths are specified: 6.2 MPa for solid or cored units, 15 MPa for hollow units (ABCB Housing Provisions, Part 5.3/5.6.2(4)). AS 3700 also specifies required characteristic strengths for design calculations.
4. Mortar and joint thickness: Mortar must comply with AS 3700 or AS 4773; the ABCB Housing Provisions allow specified volumetric mixes (Table 5.6.3). Nominal bed and perp joint thickness is 10 mm unless otherwise specified (ABCB Housing Provisions 5.6.4). Raked joint limits are given (depths not closer than 5 mm to perforations in cored unit masonry or 20 mm in hollow units; maximum raked depths 5 mm for units ≥ 90 mm wide and 10 mm for units ≥ 110 mm wide).
5. Wall ties and veneer ties: Wall ties must comply with AS 2699.1 and AS 3700 provisions. Veneer ties minimum duty depends on wind region: at or below N2 use at least light duty veneer ties; above N2 use medium duty (ABCB Housing Provisions 5.6.5). Cavity ties have similar wind-class-based minimums (see ABCB Housing Provisions 5.6.5).
6. Thickness and FRL of masonry: The NCC (Volume One, Specification S1C2 and Table S1C2a) sets minimum masonry thicknesses for deemed-to-satisfy fire-resistance levels (FRLs). Examples: masonry minimum thicknesses for specified FRLs are shown in Table S1C2a - e.g., higher FRLs require greater principal material thickness (refer to Table S1C2a: FRLs deemed to be achieved by walls - masonry in NCC Volume One, Specification 1).
7. Unreinforced vs reinforced masonry rules: AS 3700 contains separate checks and detailing for unreinforced and reinforced masonry (section and clause references within AS 3700). Where AS 3700 requires design as unreinforced masonry per Section 7, ABCB Housing Provisions may require additional checks per Table 10.3 and clause 4.1(a)(i)(C) of AS 3700 for certain piers or members (NCC Volume Two / ABCB Housing Provisions cross-reference).
8. Foundations and soil class: For compliance under ABCB Housing Provisions, masonry walls/veneers must be built on footings/slabs that comply with H1D4, and the site soil classification must be A, S or M per AS 2870 (NCC Volume Two / ABCB Housing Provisions Part 5). If outside these soil classes or other limits, full AS 3700 design and geotechnical input is required.
9. Wind and seismic actions: Masonry must be designed for wind actions in accordance with AS 1170.2 and for seismic where applicable per AS 1170.4 and AS 3700. The ABCB Housing Provisions restrict some simplified solutions to sites of wind class not more than N3 and where Appendix A of AS 1170.4 contains no specific earthquake design requirements.
10. Durability and exposure: Masonry exposure categories, unit durability and use of suitable mortars and additives are required by AS 3700 and the ABCB Housing Provisions. Products must be selected for the local exposure class (saline, industrial, etc.) and manufactured units must meet specified durability classifications (ABCB Housing Provisions Part 5.6).
11. References in NCC and Housing Provisions: See NCC Volume One - Specification S1C2 / Table S1C2a (FRLs and masonry thickness), NCC Volume Two clauses and ABCB Housing Provisions Parts 5.2-5.7 for Class 1/10 interfaces with AS 3700, and AS 3700 for full design requirements.

Residential vs Commercial

1. Residential (Class 1/10 - NCC Volume Two / ABCB Housing Provisions): Simplified provisions in the ABCB Housing Provisions allow use of AS 3700 with certain relaxations provided conditions are met: the site is in wind class not more than N3, soil class A, S or M (AS 2870), unit compressive strength minimums (6.2 MPa solid/cored; 15 MPa hollow), and footings/slabs comply with H1D4. Mortar mixing by volume in specified proportions is permitted in ABCB Housing Provisions Table 5.6.3. These relaxations permit common domestic masonry veneer and cavity walls to be constructed without full project-specific engineering, but still subject to AS 3700 detailing.
2. Commercial (Class 2-9 - NCC Volume One): For higher risk or multi-storey buildings, full compliance with AS 3700 design provisions is required and simplified ABCB Housing Provisions do not apply. Design must explicitly address wind and seismic actions per AS 1170 series, reinforcement design, and fire-resistance levels per NCC Volume One (Specification 1, Table S1C2a). Reinforced masonry, cavity detailing, control joints, and connection details generally require engineer design and certification.

Exceptions and Exemptions

1. ABCB Housing Provisions conditional relaxations for Class 1/10 in limited wind/soil/exposure conditions permit some elements to be built to simplified requirements rather than full AS 3700 design - see ABCB Housing Provisions Part 5.2 and Part 5.3 conditions (wind class ≤ N3, soil class A, S or M, not in alpine areas, unit strength minimums, H1D4 footings, etc.).
2. Where the NCC or a jurisdiction’s state schedule specifically modifies or replaces national requirements, local variations apply - these can exempt or alter some AS 3700 requirements. Always check the relevant state schedule in NCC Volume One Schedules (Schedules 4-12) and local authority requirements.
3. Alternative solutions: If a designer proposes a performance solution that departs from AS 3700, the NCC allows design by calculation, testing or verified performance reports provided the Performance Requirements are met and documentation is supplied (NCC Volume One, S1C2
4. (e) and S1C3 report requirements).

State and Territory Variations

1. The NCC requires checking state and territory schedules for modifications. Several states have specific modifications or schedules that affect masonry provisions - for example, Queensland and other jurisdictions may include specific schedule clauses that adjust allowable simplified housing provisions or set different thresholds for seismic or cyclone-prone regions. The ABCB Housing Provisions themselves note that Schedule-specific provisions may affect requirements (NCC Volume One and Volume Two cross-references).
2. Practically, designers must check the relevant state schedule in NCC 2022 Volume One (Schedules 4-12) and any local planning or building authority amendments before relying on the ABCB Housing Provisions simplifications for Class 1/10 buildings.

Practical Compliance Tips

1. Verify the governing documents up-front - confirm whether NCC Volume One or Volume Two applies, whether ABCB Housing Provisions apply, and check the relevant state schedule in NCC Volume One Schedules 4-12 before starting design.
2. Confirm wind class and soil class early - many simplified provisions depend on wind class (e.g., limit N3) and site soil classification (A, S or M per AS 2870); wrong assumptions are a common noncompliance source.
3. Select masonry units to suit exposure and strength requirements - ensure units meet the minimum compressive strengths where ABCB Housing Provisions are used (6.2 MPa solid/cored, 15 MPa hollow) and are appropriate for the exposure class according to AS 3700 and product durability classifications.
4. Use correct mortar and jointing - nominal mortar joint thickness 10 mm unless specified; follow AS 3700/AS 4773 mixing and curing guidance and ABCB Housing Provisions Table 5.6.3 where permitted. Avoid raked joints in saline or heavy industrial environments and respect raked depth limits.
5. Detail ties and connections to wind requirements - select veneer and cavity ties per AS 2699.1 and ABCB Housing Provisions 5.6.5 based on local design wind class (light vs medium duty) and ensure ties are corrosion-protected for the exposure.
6. Don’t assume unreinforced masonry is permitted without checks - some members require unreinforced masonry design per AS 3700 Section 7 and additional checks per AS 3700 Table 10.3 and clause 4.1 where the Housing Provisions cross-reference; engage an engineer where wall heights, openings or loads exceed simplified limits.
7. Document FRL and thickness compliance - where fire-resistance is required, check NCC Volume One Specification S1C2 and Table S1C2a for the minimum masonry thicknesses associated with the required FRL and include these details on drawings and specifications.

References: NCC 2022 Volume One - Specification S1C2 and Table S1C2a, NCC 2022 Volume Two and ABCB Housing Provisions Parts 5.2-5.7 (masonry sections), AS 3700 (Masonry structures), AS 2699.1 (wall ties), AS 2870 (site soil classification), AS 1170 series (wind and earthquake actions), and AS 3600/AS 1684 where concrete or timber interfaces are relevant.

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