AS 3700 Masonry Structures
A Complete Technical Guide
Introduction to AS 3700 — Scope and Purpose
AS 3700–2018 Masonry Structures is published by Standards Australia and represents the definitive technical framework for designing, detailing, and constructing masonry elements in Australia. It operates within the broader suite of Australian structural standards — alongside AS/NZS 1170 (structural loading) and the National Construction Code (NCC) — and applies to masonry used in buildings, retaining walls, fences, and other structures.
The standard covers both unreinforced masonry (URM) and reinforced masonry (RM), and addresses prestressed masonry as a specialised application. It is applicable to fired clay bricks, concrete masonry units (CMU), calcium silicate (sandlime) bricks, and autoclaved aerated concrete (AAC) blocks. Its reach extends from simple residential brick veneer through to structural masonry cores in multi-storey buildings.
Historical Context and Development
Australia has had formal masonry design standards since the 1960s. The current AS 3700 has been through several major revisions, with the 2001 edition introducing a complete shift from permissible stress to limit state design, aligning Australian practice with international structural design philosophy. The 2011 and 2018 revisions refined the durability classifications, connection details, and seismic provisions. Practitioners should always confirm they are working to the edition referenced by their project specification and NCC pathway.
Relationship with the NCC
The NCC 2022 (and transitionally NCC 2025) references AS 3700 as a Deemed-to-Satisfy (DtS) solution for structural masonry design in Class 1 through Class 10 buildings. Compliance with AS 3700 satisfies the structural Performance Requirements of NCC Section B — Structure. This relationship means that any site engineer working on masonry elements needs to understand both documents: the NCC sets the performance objective, and AS 3700 defines the technical pathway to achieving it.
AS 3700–2018 — Masonry Structures (primary design standard)
AS/NZS 1170.0–2002 — Structural Design Actions (general principles)
AS/NZS 1170.1–2002 — Permanent, Imposed and Other Actions
AS/NZS 1170.2–2021 — Wind Actions
AS 1170.4–2007 — Earthquake Actions Australia
AS 3700 Supp 1–2018 — Commentary (non-mandatory)
Masonry Materials — Units, Mortar, Grout and Ties
AS 3700 is explicit in its material requirements because the structural performance of masonry is inseparable from the quality of its constituent materials. Unlike concrete — which is a single, homogeneous material — masonry is a composite system, and the designer must specify each component with precision.
Masonry Units
Masonry units are specified under AS/NZS 4455 Masonry Units, Pavers, Flags and Segmental Retaining Wall Units. The key parameter for structural design is the unconfined compressive strength of the unit (f’uc), which directly feeds into the characteristic compressive strength of masonry (f’m).
Units are classified by their category (1 or 2) based on the consistency of their strength. Category 1 units have more reliable statistical performance and attract less conservative design penalties. In practice, most structural masonry specifications on commercial projects nominate Category 1 units to maximise design efficiency.
| Unit Type | Std Reference | Typical f’uc Range | Key Use | Notes |
|---|---|---|---|---|
| Fired Clay Brick | AS/NZS 4455.1 | 20–50 MPa | URM walls, veneer, structural | Highest durability in aggressive environments |
| Concrete Masonry Unit (CMU) | AS/NZS 4455.2 | 12–30 MPa | Reinforced masonry cores, walls | Hollow blocks permit grouting of reo |
| Calcium Silicate (Sandlime) Brick | AS/NZS 4455.3 | 14–25 MPa | Internal/external walls | Good dimensional accuracy |
| Autoclaved Aerated Concrete (AAC) | AS/NZS 4456 | 2.5–7 MPa | Non-structural, partition walls | Lightweight, good thermal/acoustic |
Mortar
Mortar serves multiple functions: it bonds units together, distributes load across bed joints, accommodates minor dimensional tolerances, and contributes to weather resistance. AS 3700 classifies mortar by proportion (mix ratio) and by compressive strength designation. The standard designates mortar types as M1 through M4, with M3 and M4 being most common in structural applications.
The characteristic compressive strength of mortar (f’j) is not used directly in most masonry capacity calculations — instead, masonry strength is tested or derived as an assembly. However, mortar designation matters significantly for durability classification, exposure category compliance, and bond strength.
Pre-mixed masonry mortars must be used within the manufacturer’s open time — typically 1–2 hours. Retempering of mortar (adding water after initial set) is explicitly prohibited under AS 3700 and significantly compromises bond strength and weather resistance. This is one of the most commonly violated requirements on active construction sites.
Grout
Grout is used to fill cores and cavities in reinforced masonry, encasing the reinforcing bars and transforming individual hollow units into a monolithic reinforced element. AS 3700 specifies minimum grout strengths (typically f’c ≥ 20 MPa) and requires grout to have sufficient workability to be consolidated around reinforcement without segregation — typically achieved through a high slump mix (200–250 mm) or self-compacting grout. Grout lifts must not exceed 1.2 m without intermediate consolidation using a vibrator.
Wall Ties and Connectors
Wall ties connect masonry leaves in cavity wall construction and connect masonry veneer to backup structures. AS 3700 specifies tie spacing and stiffness requirements depending on the exposure classification. In coastal or industrial environments, stainless steel ties (Grade 316) are mandatory. The standard also requires that ties have a drip feature or centre twist to prevent water migration across the cavity.
Structural Classification of Masonry
AS 3700 establishes a clear hierarchy of masonry structural types, each with distinct design requirements and behavioural characteristics. Understanding these classifications is the first step in selecting the appropriate design method for any given wall element.
Unreinforced Masonry (URM)
Unreinforced masonry relies entirely on the strength of the unit-mortar composite to carry applied loads. It performs well in compression but has very limited tensile strength — a critical limitation. For this reason, URM is typically used for vertically loaded walls (where gravity loads dominate and applied eccentricity is limited), low-rise load-bearing walls, and external cladding in non-seismic environments. URM must never be relied upon for significant bending (out-of-plane or in-plane) without a full capacity check, which often governs wall thickness and height.
Reinforced Masonry (RM)
Reinforced masonry incorporates steel reinforcing bars within grouted cores or cavities, enabling the assembly to carry flexural and shear loads that URM cannot sustain. RM is the standard structural system for taller masonry walls, walls subject to lateral pressure (retaining walls, below-ground walls), and buildings in seismic zones. The design philosophy mirrors reinforced concrete: steel carries tension, masonry carries compression.
Prestressed Masonry
Prestressed masonry uses post-tensioning tendons (typically high-strength steel rods or strand threaded vertically through cores) to apply a permanent compressive pre-stress to the masonry assembly. This pre-compression reduces or eliminates tensile stresses under lateral loading, allowing much thinner, taller walls to be designed without conventional reinforcement. Prestressed masonry is used in applications such as agricultural buildings, freestanding masonry walls, and sound barriers. AS 3700 Section 8 governs its design.
Veneer Masonry
Masonry veneer is a non-structural outer leaf tied to a structural backup — typically a timber or steel stud frame, a reinforced concrete slab edge, or another masonry leaf. Veneer carries only its self-weight (vertically to supports) and out-of-plane wind pressure (laterally to ties). AS 3700 contains specific requirements for veneer support, tie stiffness, expansion/movement joints, and the maximum unsupported height of veneer panels.
Design Principles — Limit State Design Framework
AS 3700 adopts the limit state design (LSD) framework consistent with AS/NZS 1170.0. This approach ensures that structures are designed to have an acceptable probability of remaining fit for purpose throughout their design life, considering both the ultimate limit state (ULS — structural failure, collapse) and serviceability limit state (SLS — deformation, cracking, vibration).
Design Action Combinations
All masonry structural elements must be designed such that the design action effect (Ed) does not exceed the design capacity (φRn) for every relevant limit state:
E* = Design action effect (factored load combination from AS/NZS 1170.0)
φ = Capacity reduction factor (specific to masonry failure mode)
Rn = Nominal capacity of masonry element (calculated from AS 3700 clauses)
The load combinations for masonry are identical to those in AS/NZS 1170.0. Critical combinations for masonry walls typically include:
- 1.35G (permanent action dominant)
- 1.2G + 1.5Q (gravity + live load)
- 1.2G + Wu + ψcQ (wind dominant — typically critical for slender walls)
- 0.9G + Wu (wind uplift/overturning with minimum gravity)
- 1.2G + Eu + ψcQ (earthquake dominant — applies in seismic zones)
Capacity Reduction Factors (φ)
AS 3700 specifies capacity reduction factors that reflect the variability of masonry material properties and the consequences of each failure mode. These are lower than the equivalent factors for concrete, reflecting the greater material variability of masonry assemblies.
| Failure Mode | φ Factor | Notes |
|---|---|---|
| Compression (unreinforced) | 0.45 | Reduced for slenderness effects |
| Compression (reinforced) | 0.60 | Higher due to reinforcement ductility |
| Flexural tension (bed joints) | 0.60 | Bond-dependent — critical mode |
| Flexural tension (stepped) | 0.60 | Diagonal stepped crack pattern |
| Shear (unreinforced) | 0.60 | Mortar friction contribution |
| Shear (reinforced) | 0.75 | Reo provides ductility reserve |
| Connections / ties | 0.55 | Eccentricity and pull-out combined |
Characteristic Compressive Strength — f’m
The characteristic compressive strength of masonry (f’m) is the cornerstone of all structural masonry design. It can be derived by two methods under AS 3700: by testing masonry assemblies (prisms) in accordance with AS 3700 Appendix A and applying statistical reduction, or by using the table method which pairs unit strength and mortar type to give a tabulated f’m value.
k = Constant depending on unit type and mortar designation (typically 0.9–1.4 from AS 3700 Table 3.1)
f’uc = Characteristic unconfined compressive strength of unit (MPa)
Example: Clay brick f’uc = 25 MPa, M3 mortar → k = 1.0 → f’m ≈ 5.0 MPa
Compression Capacity of Masonry Walls
Compression is the natural strength of masonry. Gravity loads — from floors, roofs, and self-weight — are carried in compression through masonry walls to foundations. However, masonry under compression can fail through crushing, through lateral instability (buckling of slender walls), or through combined compression and bending (eccentric loading).
Slenderness and Effective Height
The slenderness ratio of a masonry wall is the ratio of its effective height (He) to its effective thickness (te). AS 3700 limits slenderness to prevent lateral instability. For a simple wall pinned top and bottom, He = H (clear storey height). The effective height is modified by the degree of rotational restraint at the top and bottom supports — fixed or partially fixed conditions reduce He and therefore improve the compression capacity.
te = Effective thickness (for cavity walls, te accounts for both leaves if tied)
Limit: SR ≤ 26 for solid walls; SR ≤ 35 for walls with full restraint top and bottom
Note: Lower SR limits apply for walls subject to significant wind or eccentric loads.
Capacity Reduction for Slenderness and Eccentricity
The compression capacity of a masonry wall is reduced by both slenderness (which introduces amplified bending from P-delta effects) and load eccentricity (which arises from floor beams bearing asymmetrically on the wall, or from out-of-plumb construction). AS 3700 uses a capacity reduction factor for compression (k) that combines both effects into a single reduction multiplier applied to the fundamental compression capacity:
f’m = Characteristic compressive strength of masonry (MPa)
tm = Effective masonry width (m)
t = Wall thickness (mm)
k = Combined slenderness and eccentricity reduction factor from AS 3700 Table 7.3
The factor k reduces rapidly as SR increases beyond 15, making wall thickness selection critical.
Flexural Capacity — Out-of-Plane and In-Plane Bending
Masonry walls are subjected to bending by wind pressure, retained earth pressure, or eccentric vertical loads. The design must address both out-of-plane bending (the wall acts as a vertical or horizontal spanning element between supports) and in-plane bending (the wall acts as a shear wall with overturning moment). Unreinforced masonry has very limited tensile capacity; reinforced masonry can carry much larger bending moments through the steel-grout composite action.
Out-of-Plane Flexure — Unreinforced
For URM walls under out-of-plane bending (e.g., wind pressure on an external wall), cracking develops in one of two modes: failure through the bed joint (horizontal cracking — governed by the flexural tensile strength of mortar bond, f’mt) or stepped failure through the units and perpend joints (diagonal cracking — governed by the combined tensile and bond strength in both directions). AS 3700 uses orthogonal strength ratios to account for the directional nature of masonry tensile resistance.
f’mt = Characteristic flexural tensile strength of masonry (0.2 MPa for bed joint failure, typical)
Z = Section modulus of wall cross-section (= t²/6 per metre run, where t = wall thickness in mm)
φ = 0.60 for flexural tension
For compressive face (where gravity load acts): bending capacity is enhanced by the axial compression (pre-stress effect), and the governing check shifts to the tensile face.
Two-Way Spanning Masonry
When a masonry wall is supported on all four edges (or three edges), it can span in two directions simultaneously under out-of-plane pressure. AS 3700 provides a yield-line analysis approach using orthogonal strength ratios (α) to distribute the applied pressure between the vertical and horizontal spanning directions. The ratio α = f’mth / f’mtv, where f’mth is the horizontal strip flexural tensile strength and f’mtv is the vertical strip value. For most masonry, α is less than 1.0 because the grain structure of clay bricks gives higher tensile bond parallel to the bed than perpendicular to it.
In-Plane Flexure and Shear Wall Behaviour
When wind or seismic loads act parallel to the plane of a masonry wall, the wall acts as a shear wall. It resists in-plane shear and carries an overturning moment. The in-plane flexural capacity of a URM shear wall is governed by either rocking (rigid body rotation about the toe) or cracking through bed joints. For reinforced masonry shear walls, the section analysis parallels reinforced concrete, with the reinforcement carrying tension and masonry carrying compression in a stress-block model.
Shear Design in Masonry
Shear in masonry can occur in two planes: in-plane shear (parallel to the wall face, acting on horizontal sections), which governs the design of shear walls under lateral loading; and out-of-plane shear (perpendicular to the wall face), which is rarely critical in typical masonry walls but must be checked near supports.
In-Plane Shear Capacity — Unreinforced
The in-plane shear capacity of URM relies on the frictional sliding resistance of bed joints plus any cohesion contribution from the mortar bond. AS 3700 models this as a Coulomb friction relationship:
μ = Coefficient of friction = 0.3 for unreinforced masonry in AS 3700
fd = Design compressive stress on the section (from gravity loads — compression enhances shear capacity)
Ab = Bedded area of the shear section (plan area of horizontal bed joints in the failure section)
φ = 0.60
In-Plane Shear Capacity — Reinforced
In reinforced masonry shear walls, horizontal reinforcing bars (placed in bond beams at specified intervals) provide an additional shear mechanism — dowel action and truss analogy contribution — significantly increasing shear capacity. The total shear capacity is additive: masonry mechanism (Vm) plus reinforcement mechanism (Vs).
The most effective strategy to increase masonry shear capacity is to increase the pre-compression on the wall (by adding vertical load) before adding horizontal reinforcement. In low-to-medium seismic zones, increasing gravity load pathway to the wall is often more cost-effective than adding horizontal reinforcement, which requires additional bond beams and grouted cores.
Lateral Load Resistance and Wind Design
Wind loading is the primary lateral design action for most masonry walls in Australia. The wind pressure applied to a masonry wall panel is determined by AS/NZS 1170.2, which defines design wind speeds based on geographic region (A, B, C, D), terrain category, shielding, and topographic effects. The resulting design wind pressure (p*) is then applied to the masonry wall panel, which must transfer it to supports through spanning action, ties, or pilasters.
Panel Support Conditions
Masonry wall panels can span vertically between floor slabs, horizontally between pilasters or columns, or in two directions when supported on multiple edges. The choice of support conditions fundamentally affects the required wall thickness. Vertical spanning (between concrete floor slabs) is the most common configuration and the most structurally efficient because concrete slabs are stiff, reliable supports.
Wind Design Procedure
- Determine the site wind speed (Vdes) from AS/NZS 1170.2 based on location and importance level.
- Calculate design wind pressure: p* = 0.5 ρ C_fig C_dyn Vdes² (using appropriate pressure coefficients)
- Determine the applied bending moment on the wall panel based on the span and support conditions.
- Check flexural capacity of the masonry section (Section 6 approach).
- Check that tie spacing and tie capacity are adequate to transfer wind reactions to supports.
- Verify slenderness limits are not exceeded for the chosen wall thickness.
Wind Regions in Australia
For masonry design in Sydney (Region A — general non-cyclonic) the design wind speed is significantly less demanding than in Queensland coastal zones (Region C or D — cyclonic). This directly affects masonry panel thickness, tie spacing, and whether reinforcement is required. A wall that works in Sydney may need to be redesigned from scratch for a Darwin project.
Region A — Non-cyclonic, most of SE Australia (Sydney, Melbourne, Adelaide). Vdes typically 40–50 m/s for Importance Level 2 structures.
Region B — Intermediate, inland Queensland and coastal SA/WA. Vdes 50–60 m/s.
Region C — Cyclonic fringe areas, tropical coast. Vdes 60–80 m/s.
Region D — Severe cyclonic, north-west WA and parts of NT. Vdes > 85 m/s. Masonry design in Region D often requires reinforcement and/or prestress regardless of height.
Reinforced and Prestressed Masonry
Reinforced masonry extends the structural capability of masonry by introducing deformed steel bars into grouted cores or cavities. The design approach in AS 3700 Section 7 and Section 8 closely mirrors reinforced concrete design, with masonry replacing concrete as the compression medium. This is not coincidental — masonry and reinforced concrete share the same structural logic: a high-compression material (concrete or masonry) working in concert with high-tensile material (steel reinforcing bars).
Flexural Design of Reinforced Masonry
For singly-reinforced masonry sections in bending, the design follows a rectangular stress-block model analogous to AS 3600 for concrete. The neutral axis depth is determined by equilibrium, and the design moment capacity is calculated from the couple between the compression resultant in masonry and the tension resultant in steel.
fsy = Yield strength of reinforcement = 500 MPa for Grade N bars (deformed)
d = Effective depth from compression face to centroid of tensile steel (mm)
a = Depth of rectangular stress block = Ast · fsy / (0.85 · f’m · b)
b = Width of compression zone (usually = unit width for single-core sections)
φ = 0.60 for reinforced masonry in bending
Minimum Reinforcement Requirements
AS 3700 specifies minimum steel ratios to ensure ductile behaviour and avoid brittle fracture upon first cracking. The minimum steel ratio for reinforced masonry walls is generally lower than reinforced concrete, reflecting the beneficial contribution of masonry self-weight (pre-compression) to capacity. Bond strength, development length, and lap splice requirements for masonry reinforcement are also specified in AS 3700 Section 7 and must be checked carefully — the grout-to-steel bond is generally lower than concrete-to-steel bond, requiring longer development lengths.
Prestressed Masonry
Post-tensioned masonry is the most sophisticated form of masonry construction in AS 3700. High-strength steel rods or strand are anchored at the base and stressed from the top, creating a uniform vertical pre-compression throughout the wall height. This pre-compression effectively eliminates tensile stresses under moderate lateral loading, enabling very slender walls (SR approaching 35) and long spans without conventional reinforcement.
The design must account for initial prestress (immediate losses from elastic shortening), long-term prestress losses (creep, shrinkage, steel relaxation), and the decompression moment — the moment at which the pre-compression is overcome and tensile stresses begin to develop. The ultimate limit state involves the tendon reaching its yield load while masonry crushes at the compression toe — a brittle failure mode that AS 3700 requires to be guarded against through minimum pre-compression checks.
Durability, Construction Tolerances and Quality Assurance
Structural design capacity is meaningless if the masonry is constructed incorrectly or deteriorates prematurely. AS 3700 dedicates significant sections to durability requirements, construction practices, and quality assurance — reflecting the reality that masonry is assembled in-situ by tradespeople and is therefore highly sensitive to workmanship quality.
Durability and Exposure Classification
AS 3700 classifies masonry durability requirements by exposure environment, which determines the minimum unit type, mortar type, and finish required. The classification framework maps to the NCC and AS 3700 Table 5.1:
| Exposure Class | Environment Description | Min. Unit Requirement | Min. Mortar | Tie Requirement |
|---|---|---|---|---|
| R0 | Interior — protected from weather | Any unit | M1 | Galvanised (Z275) |
| R1 | Exposed to weather — not aggressive | Non-porous fired clay or CMU | M2 | Galvanised (Z600) or SS |
| R2 | Moderate — urban, some industrial | High-quality fired clay or CMU | M3 | Stainless Steel 304 |
| R3 | Severe — coastal ≤1 km from sea | Highly durable units | M4 | Stainless Steel 316 |
| R4 | Very severe — direct spray, aggressive industrial | High durability + surface treatment | M4 + sealant | SS 316 + isolation |
Construction Tolerances
AS 3700 Table 14.1 specifies construction tolerances that define the maximum permissible deviation from design position for completed masonry work. Key tolerances include:
- Level of bed joints: ±10 mm over any 10 m length; ±5 mm in any 5 m length
- Plumb: ±10 mm over storey height (typically 3 m); ±25 mm over full building height
- Straightness in plan: ±10 mm over any 5 m length
- Location in plan: ±10 mm from design position
- Cross-sectional thickness: –3 mm to +6 mm from specified dimensions
- Joint thickness: 10 mm nominal ±3 mm
From site observation, the most frequently violated tolerances are plumb of cavity walls (particularly where inner and outer leaves are built independently at different rates) and mortar joint consistency. Inconsistent mortar joint thickness is not merely aesthetic — it directly reduces the contact area between units, reducing both compression and bond capacity. Inspections should measure and record joint thickness at least daily during masonry construction.
Movement Joints
Masonry is subject to thermal expansion (all masonry), moisture expansion (clay bricks grow permanently after firing), and moisture shrinkage (concrete masonry shrinks as it dries). Without properly designed and located movement joints, these dimensional changes produce cracking that bypasses the structural system and can compromise durability and serviceability.
AS 3700 and the BCA require movement joints at maximum 6–8 m intervals in clay brickwork, and at 4–6 m intervals in concrete masonry (which shrinks rather than expands). Movement joints must be free of mortar, fully filled with a compressible backer rod and sealant, and coordinated with structural movement joints in the building frame.
Inspection and Testing
AS 3700 Section 15 prescribes inspection categories aligned with the consequence of masonry failure:
- Category 1: Simple low-risk masonry — visual inspection during construction, no testing required
- Category 2: Standard residential/commercial masonry — inspection at key stages, material testing of samples
- Category 3: High-consequence masonry (large shear walls, high-rise) — independent third-party inspection, mandatory material testing, prism testing to confirm f’m
Site Engineering Perspective — Practical Application
The foregoing design principles are most valuable when anchored to the realities of the construction site. As a site engineer responsible for masonry construction on high-rise or commercial projects, the gap between design intent and constructed outcome is your domain. This final section addresses how AS 3700 requirements manifest in day-to-day site practice.
Pre-Construction Review
Before masonry construction commences, the site engineer should conduct a thorough review of structural drawings, engineering specifications, and material submittals against AS 3700 requirements. Key items to verify include: masonry unit specification and test data confirming f’uc and durability classification; mortar specification and batch control method; wall tie specification against exposure class; reinforcement layout and grout specification for reinforced elements; and confirmation that movement joint locations match the structural design.
During Construction — Critical Hold Points
The following should be treated as inspection hold points — construction must not proceed past these stages without engineer sign-off:
- Starter bar / dowel placement: Position, size, and spacing of vertical starter bars before grouting of first course
- Lift height before grouting: Maximum 1.2 m masonry height before grout is poured and consolidated
- Horizontal reinforcement placement: Bond beam bars in position and tied before grouting
- Cavity clearance: Clean out inspections of cavities and cores before final grouting — mortar droppings and debris must be removed
- Movement joint integrity: Joints must be free of mortar before being sealed
- Pre-stress stressing: All PT masonry must be stressed to specified load, recorded, and documented before structural loads are applied
Common Defects and Non-Conformances
Based on common site observations in the Australian construction industry, the following defects are frequently encountered in masonry work and require proactive management:
| Defect Type | AS 3700 Clause | Structural Consequence | Remediation |
|---|---|---|---|
| Retempering of mortar | Section 14 | Loss of bond strength, reduced durability | Remove and re-lay affected courses |
| Voids in grout fill | Section 14 | Reduced RM capacity — reo may be unbonded | Core drill and grout injection after test coring |
| Incorrect tie spacing | Table 9.1 | Insufficient lateral support to veneer/leaf | Retrospective tie installation (specialist anchors) |
| Out-of-plumb walls | Table 14.1 | Increased eccentricity → reduced compression capacity | Engineering assessment of as-built condition |
| Mortar joints bridging movement joints | Section 13 | Restrained movement → cracking / spalling | Cut out joint, install backer rod and sealant |
| Wrong unit specification | Section 5 | Potential durability failure and reduced strength | Manufacturer test certificates; engineer review |
Documentation and Records
Masonry construction documentation should include: signed inspection hold-point records, material delivery dockets and test certificates, mortar batch records, grout pour records with dates and lift heights, stressing records for PT masonry, and photographs of reinforcement placement before grouting. This documentation forms part of the project’s structural record and is essential for any future investigation of structural performance, building alterations, or insurance claims.
Interface with Other Trades and Disciplines
Masonry walls on high-rise and commercial projects interface with multiple other trades and disciplines. The structural engineer sets out the design intent; the site engineer must manage the interface. Critical coordination items include: penetrations through structural masonry (each one reduces wall capacity and requires engineering sign-off); temporary propping of masonry during construction before floor slabs cast; tie-back connections where masonry abuts concrete or steel frames; and coordination of waterproofing membranes at the base of cavity walls to ensure effective cavity drainage.
Seismic Considerations for NSW
Sydney falls within a moderate seismic hazard zone under AS 1170.4. While not a high seismic risk compared to New Zealand or California, unreinforced masonry buildings in Sydney have demonstrated poor seismic performance historically, and AS 1170.4 requires masonry in Importance Level 2 and 3 buildings to be designed for earthquake actions. For most Sydney commercial masonry, this means: reinforcement in critical walls even where wind alone would not require it, connection of non-structural masonry partitions and veneers to prevent out-of-plane collapse, and specific detailing of diaphragm connections between floor slabs and masonry walls.
Conclusion
AS 3700 is a mature, comprehensive standard that reflects decades of research and practical experience with masonry construction in Australian conditions. From the foundational material properties through to the design of complex reinforced and prestressed masonry systems, it provides a complete framework for producing safe, durable, and efficient masonry structures.
For the practising engineer or site professional, the most important discipline is to treat masonry not as a simple traditional material but as an engineered system — one whose performance depends equally on sound design, correct specification, and rigorous site execution. The standard’s provisions only deliver their intended safety margin when the materials specified are the materials delivered, and when the construction tolerances and quality requirements are genuinely achieved and documented on site.
As Australia’s building codes continue to evolve under the NCC 2025 framework, masonry remains a relevant, competitive, and sustainable structural material — particularly for mid-rise residential and commercial construction, where its inherent fire resistance, acoustic performance, and durability make it a strong choice when properly designed and built to AS 3700.
AS 3700–2018 — Available from SAI Global (saiglobal.com)
AS 3700 Supplement 1–2018 — Commentary (highly recommended for design intent)
Think Brick Australia — thinkbrick.com.au (technical design guides, detailing manuals)
Concrete Masonry Association of Australia (CMAA) — cmaa.com.au (CMU design guides)
NCC 2022 Volume 1 — ncc.abcb.gov.au (regulatory framework)
MEng Structural Engineering, University of Technology Sydney (UTS)
5+ years delivering residential and commercial high-rise projects