Standards Australia · Published 2018

AS 3700:2018

Masonry Structures

AS 3700:2018 sets out the minimum requirements for the design and construction of masonry structures, including unreinforced, reinforced and prestressed masonry in clay brick, concrete masonry, calcium silicate, autoclaved aerated concrete and natural stone. It covers structural design, materials, mortars and grouts, durability, fire resistance, and connections to supporting structure. The 2018 edition incorporates significant changes from the 2011 edition in out-of-plane bending capacity calculations (Section 7), seismic detailing requirements (Section 9, aligned with AS 1170.4), and durability classifications (Section 5). AS 3700 is the deemed-to-satisfy reference for masonry structures under the National Construction Code (NCC) Volume One Section B and is the controlling design standard for unreinforced masonry assessment in TRSC heritage engagements. The standard is applied alongside AS 1170 series loading standards, AS 4773 (masonry in small buildings), and the AEFAC technical notes for masonry-anchorage applications.

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TRSC Engineering Interpretation

AS 3700:2018 is the most-referenced masonry standard in TRSC heritage practice. The standard governs every unreinforced masonry capacity calculation we perform — out-of-plane bending capacity of boundary walls and gable walls, in-plane shear capacity for in-plane loading, and connection capacity at floor and roof diaphragms. Three application points matter for existing-asset assessment. First, the standard requires characteristic masonry properties (compressive strength f'm, flexural tensile strength fmt, characteristic shear strength fvm) that are not typically known for pre-1940 construction. AS 3700 Section 3 provides default characteristic values for modern masonry products; for heritage masonry, those defaults are not applicable. TRSC's standard practice is to extract masonry units and mortar samples for laboratory characterisation when the calculation is decision-controlling — typically compressive strength tests on extracted bricks per AS 3700 Appendix B, and mortar composition analysis to identify the binder type (lime vs. cement vs. mixed). Without measured properties, capacity calculations on heritage masonry default to conservative assumed values that frequently understate residual capacity by 30-50%. Second, AS 3700 out-of-plane bending capacity (Section 7) is the controlling check on unreinforced masonry boundary walls and gable walls, and the calculation is sensitive to wall thickness, support conditions, and applied moment from earthquake or wind. The Prince Consort Hotel boundary-wall assessment under AS 3700-2018 / AS 1170.4-2007 is a worked example: the calculation confirmed compliance with measured-property input that would have failed with default assumed values. Third, the standard's connections section (Section 8) governs masonry-to-supporting-structure connection design, including the design of brick ties (for which Helifix CemTie is the heritage-compatible default specification under AS 3700 Appendix A pull-out testing). For heritage strengthening designs, AS 3700 provides the pull-out testing methodology and the partial safety factors that determine the design tie capacity. TRSC remediation specifications cite AS 3700 Appendix A as the controlling test method for site-witnessed pull-out verification.

Form 15 RPEQ Certification Implications

Form 15 RPEQ certification on heritage masonry routinely references AS 3700:2018 in conjunction with AS 1170.4-2007. The Form 15 declaration is conditional on the masonry meeting the design out-of-plane bending capacity and connection capacity under the design loading. For heritage assets where measured masonry properties differ from AS 3700 default characteristic values, the Form 15 supporting investigation file must include the laboratory characterisation results (compressive strength, mortar composition, flexural tensile strength where determinable) and the engineering basis for using the measured properties in the calculation rather than the standard defaults. The Helifix CemTie installations on the Prince Consort Hotel were Form 15-certified against AS 3700:2018 Appendix A pull-out testing, with the test results retained in the investigation file.

Frequently Asked Questions

Engineering questions about AS 3700:2018

How does TRSC characterise masonry properties for pre-1940 buildings?

TRSC extracts masonry unit samples (typically 3-5 bricks per representative wall area) for laboratory compressive strength testing per AS 3700 Appendix B, and mortar samples for composition analysis to identify the binder type. The measured characteristic compressive strength is then used in AS 3700 capacity calculations rather than default assumed values, which for heritage masonry are typically conservative by 30-50%. The methodology was applied on the Prince Consort Hotel and Victory Hotel investigations, where measured properties drove the structural decision.

What is the relationship between AS 3700 and AS 1170.4 in masonry assessment?

AS 1170.4-2007 provides the seismic design action; AS 3700:2018 provides the masonry capacity. The combination is applied in heritage out-of-plane bending checks where the seismic action is typically the controlling load case for unreinforced masonry walls. The check is whether the AS 3700 calculated bending capacity exceeds the AS 1170.4 design moment for the importance level and sub-soil class of the asset.

Are Helifix CemTie installations governed by AS 3700?

Yes. AS 3700 Section 8 governs masonry-to-structure connection design and Appendix A specifies the pull-out testing methodology used to verify tie capacity on site. TRSC heritage remediation specifications cite AS 3700 Appendix A as the controlling test method, and the test results are retained in the Form 15 investigation file as evidence supporting the certification.

When should masonry NOT be assessed under AS 3700?

Masonry that does not fall within the AS 3700 scope — for example, dry-stacked rubble masonry, certain hand-formed clay masonry from before approximately 1880, or non-Australian construction systems such as American common-bond brickwork — may require alternative assessment frameworks (typically the international heritage-structures literature, or expert-judgement supplemented by physical testing). TRSC explicitly states the design basis in the investigation report when AS 3700 is applied outside its native scope, including any reduced confidence factors used to reflect the standard's limitations.

Relevant Services

Heritage Structural Engineering

Relevant Materials

Sources & Further Reading

GovernmentAS 3700:2018 — Standards Australia