AS 3700:2018: masonry structures
AS 3700:2018 governs masonry structures in Australia. Key requirements for veneer, cavity, articulation joints, DPC, weep holes, and NCC H1D5 DTS compliance.
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AS 3700:2018 is the Australian Standard for masonry structures. For residential Class 1 and Class 10 builds, compliance with AS 3700 satisfies the NCC 2022 structural performance requirement under H1D5, alongside the simpler companion standard AS 4773 (masonry in small buildings). The most common defects on site are failing DPC installation, missing or blocked articulation joints, and cavity breaches. In a 2025 NSW Building Commission campaign targeting 850 residential sites, improper DPC and incorrect control/articulation joints were the top masonry rectification triggers (verified 2026-05-08, NSW Building Commission). The standard is paywalled; the ABCB Housing Provisions 2022 Section 5 covers the practical DTS rules for residential masonry and is free.
In plain English
AS 3700:2018 is the Australian Standard that sets minimum requirements for the design and construction of unreinforced, reinforced, and prestressed masonry, including built-in components such as wall ties, lintels, and damp-proof courses.
The 2018 edition superseded AS 3700:2011. Key changes in 2018 included increased capacity reduction factors for compression in hollow masonry with wide-spaced reinforcement, provisions for stack-bonded masonry, compressive strength of grouted masonry, and minor consistency changes with AS 4773.
For most residential projects (Class 1 and Class 10), the companion standard AS 4773 (Masonry in small buildings, Parts 1 and 2) is the more practical everyday reference. AS 4773 was developed specifically for houses and small buildings within defined geometric limits. AS 3700 applies where AS 4773 limits are exceeded (larger or more complex buildings, Class 2 apartment buildings, structural engineering design), or where the engineer of record elects to design fully to AS 3700.
Either standard satisfies NCC 2022 Volume Two Clause H1D5 as a Deemed-to-Satisfy (DTS) path for residential masonry.
What it requires
NCC 2022 reference points
NCC 2022 Volume Two Clause H1D5 specifies that masonry in Class 1 and Class 10 buildings must be designed and constructed in accordance with either AS 3700 or AS 4773.1 and AS 4773.2. This applies to (verified 2026-05-08, NCC 2022 Vol 2 H1D5):
| Masonry type | Standard options |
|---|---|
| Masonry veneer | AS 3700 or AS 4773.1 + AS 4773.2 |
| Cavity masonry (unreinforced) | AS 3700 or AS 4773.1 + AS 4773.2 |
| Single leaf unreinforced | AS 3700 or AS 4773.1 + AS 4773.2 |
| Reinforced masonry | AS 3700 (with specific clause modifications) |
| Isolated masonry piers | AS 3700 (with specific clause modifications) |
| Masonry accessories | AS 3700 or AS 4773.1 + AS 4773.2 |
Class 2 apartment buildings must use AS 3700. AS 4773 does not apply to Class 2.
The ABCB Housing Provisions Standard 2022, Section 5 (Masonry) provides the DTS rules for residential masonry in plain, accessible form. The Housing Provisions are free at ncc.abcb.gov.au.
Masonry veneer (Housing Provisions Part 5.2)
Masonry veneer walls must not exceed 8.5 m in height above adjacent finished ground level. Openings must be spanned by steel lintels, except those not exceeding 500 mm wide if adequately supported (verified 2026-05-08, NCC Housing Provisions 5.2).
The cavity between the veneer leaf and the backing must be 25 mm to 75 mm clear width for masonry veneer, and 35 mm to 75 mm for cavity masonry. The cavity must remain free of mortar droppings (snots) throughout the lay.
Articulation joints (Housing Provisions 5.6.8)
Articulation joints are vertical control joints built into masonry walls to accommodate movement from thermal expansion, moisture changes, and foundation settlement. They must have a minimum width of 10 mm and be filled with a flexible sealant backed by compressible foam or a purpose-made backer rod.
Spacing requirements per Housing Provisions 5.6.8 (verified 2026-05-08, NCC Housing Provisions 5.6):
| Wall condition | Maximum spacing | Placement |
|---|---|---|
| Straight wall, openings under 900 mm x 900 mm | 6 m centres | Within 4.5 m of corners, not closer than 470 mm to a corner |
| Straight wall, openings over 900 mm x 900 mm | 5 m centres | Not more than 1.2 m from any opening |
| At height changes exceeding 20% | At the change point | Continuous through veneer only where veneer leaf |
| At thickness changes, footing joints, material junctions | At the change point | Continuous |
Articulation joints are the defect most commonly missed on site. The joint must be continuous through the full height of the masonry leaf, properly backed, and sealed. A joint that is built in only partially (filled with mortar snots, not taken through the full height, or bridged at the brick course level) provides no movement capacity and will crack adjacent brickwork instead.
Wall ties (Housing Provisions 5.6.5)
Wall ties must comply with AS 2699.1 and must be selected for the wind class and masonry type:
| Application | Wind class | Tie duty |
|---|---|---|
| Masonry veneer | N2 or below | Light duty |
| Masonry veneer | Above N2 | Medium duty |
| Cavity masonry | N1 | Light duty |
| Cavity masonry | Above N1 | Medium duty |
Maximum tie spacing is 600 mm horizontal and vertical for cavity and solid masonry. Corrosion protection requirements increase with coastal proximity: Grade 316L stainless steel within breaking surf zones, 470 g/m2 galvanised within 10 km of coast, standard 300 g/m2 galvanising elsewhere (verified 2026-05-08, NCC Housing Provisions 5.6).
Damp-proof courses and flashings (Housing Provisions 5.7.3 and 5.7.4)
DPC and flashing materials must comply with AS/NZS 2904 or be from the acceptable list in Housing Provisions 5.7.3, including embossed black polyethylene (0.5 mm nominal), polyethylene-coated aluminium-core sheet (0.5 mm total), or bitumen-impregnated materials (minimum 2.5 mm thick).
DPC must extend the full width of the masonry and remain visible externally after finishes are applied (it must not be buried in render). Key installation positions (verified 2026-05-08, NSW Building Commission):
- Bottom perimeter of walls at slab or footing level
- Minimum 150 mm above adjacent ground level (75 mm above sloped paved areas; 50 mm above protected paved areas)
- Below window and door sills
- Where masonry passes through or abuts roofs
Head flashings above openings must extend at least 150 mm beyond the reveals, turn up in the cavity at least 150 mm above the opening, and be embedded at least 30 mm into the masonry leaf (verified 2026-05-08, NCC Housing Provisions 5.7.4).
Weep holes (Housing Provisions 5.7.5)
Weep holes are open perpend joints placed in the outer masonry leaf immediately above any flashing or DPC. Requirements (verified 2026-05-08, NCC Housing Provisions 5.7.5):
- Minimum 50 mm height, full width of the vertical mortar joint
- Spaced at maximum 1.2 m centres
- Required immediately above every DPC and flashing location
Weep holes are not required below window and door sills, or above head openings less than 1.2 m wide.
Mortar mixes (Housing Provisions 5.6.3)
Mortar proportions (cement:lime:sand by volume) depend on masonry unit exposure class:
| Exposure | Proportions (cement:lime:sand) |
|---|---|
| Protected | 1:2:9 |
| General purpose | 1:1:6 |
| Exposure class | 1:0.5:4.5 |
Single leaf masonry weatherproofing (Housing Provisions 5.7.6)
Single-skin masonry used externally requires a waterproof coating from roof to floor level. Acceptable finishes include three coats 100% acrylic exterior gloss paint, or one cement-based coat plus two acrylic coats. Clear water repellent is allowed where the roof overhang is at least 1,500 mm (verified 2026-05-08, NCC Housing Provisions 5.7).
What it doesn’t cover
AS 3700 does not cover:
- Masonry in small buildings within geometric limits: use AS 4773 Parts 1 and 2 as the practical DTS path for Class 1 residential
- Masonry retaining walls not associated with a building (separate structural design required)
- Swimming pool shell masonry (pools use separate pool construction standards)
- Masonry in Class 5 to Class 9 buildings (commercial; covered by NCC Volume One and engineering design)
- Earth masonry (rammed earth, adobe, mud brick): not covered by AS 3700; performance solution required under the NCC
Practical implications
AS 3700 versus AS 4773 on a house
For a standard Class 1 house or townhouse, the brickie and the builder will almost always work to AS 4773 and the Housing Provisions, not the full AS 3700 design standard. AS 4773 was written for exactly this use case. The builder’s obligation is that the masonry system (veneer, cavity, or single leaf) sits within the Housing Provisions’ prescribed limits for height, wind class, and pier sizing. If it does, AS 4773 covers it.
AS 3700 comes in when:
- The building is Class 2 (apartments)
- The structural engineer has designed a masonry element that sits outside AS 4773 limits
- The masonry is complex (large reinforced piers, prestressed masonry, unusual loading)
- The certifier or engineer requires a full AS 3700 design submission
Sequencing on site
The critical masonry sequence:
- Footings and slab complete, DPC installed at base course level before first course of masonry
- First course laid to line with weep holes formed at DPC level
- Cavity kept clear of mortar drops (snots) throughout the build, especially in lower courses
- Wall ties installed at correct centres and duty as the inner frame rises
- Articulation joints formed at designed locations, continuous through full leaf height, backed with foam
- Flashing and DPC installed above openings (lintels), and at any roof abutment, before continuing the masonry
- Weep holes formed immediately above each flashing course
- Single-leaf external masonry coated before render or paint applied
Common defects and inspection points
These are the failures found repeatedly in building inspections and warranty claims:
| Defect | Cause | Impact |
|---|---|---|
| DPC not visible externally | Buried in render or mortar | Cannot be inspected; moisture pathway from ground into wall |
| DPC below 150 mm above ground | Set too low or ground built up after construction | Rising damp in wall cavity |
| Articulation joints missing or filled | Not formed, or filled with mortar during cavity clean | Diagonal cracking in brickwork as thermal movement accumulates |
| Articulation joints not continuous | Joint stopped partway up the wall height | Partial movement only; cracking resumes above the stopped joint |
| Weep holes blocked or missing | Mortar snots blocking cavity at base course; weep holes not formed | Moisture ponding in cavity; rising damp; corrosion of wall ties and steel lintels |
| Wall ties wrong duty for wind class | Light duty installed in exposed coastal locations | Veneer detachment risk in high-wind events |
| Wall ties not installed | Omitted in runs between studs | Veneer not connected to frame; collapse risk |
| Cavity width outside range | Cavity too wide (ties overstressed) or too narrow (mortar bridging) | Structural risk or cavity function lost |
| Mortar droppings in cavity | Not cleared during construction | Bridge moisture path; restrict drainage; corrode ties |
Masonry workmanship tolerances
The maximum permitted deviation for finished brickwork in residential construction is pending verified member access to the HIA Guide to Materials and Workmanship. Specifically: [HIA-035]
The maximum permitted deviation for wall straightness (under a straightedge) is also pending verified member access to the HIA Guide. [HIA-036]
For AS 3700 structural design, the standard itself includes workmanship tolerances for level, plumb, and position of masonry elements. The full tolerance schedule is in AS 3700:2018 Section 10.
Source link
Standards Australia: AS 3700:2018 product page (verified 2026-05-08). The standard is paywalled. The ABCB Housing Provisions 2022 Section 5 (Masonry) is the free residential DTS document at ncc.abcb.gov.au.
References
- Standards Australia, AS 3700:2018 Masonry structures (product page). https://store.standards.org.au/product/as-3700-2018 (verified 2026-05-08).
- Australian Building Codes Board, NCC 2022 Volume Two, Part H1 Structure, Clause H1D5 Masonry. https://ncc.abcb.gov.au/editions/ncc-2022/adopted/volume-two/h-class-1-and-10-buildings/part-h1-structure (verified 2026-05-08).
- Australian Building Codes Board, ABCB Housing Provisions Standard 2022, Section 5 Masonry. https://ncc.abcb.gov.au/editions/ncc-2022/adopted/housing-provisions/5-masonry (verified 2026-05-08).
- Australian Building Codes Board, ABCB Housing Provisions Standard 2022, Part 5.6 Masonry components and accessories. https://ncc.abcb.gov.au/editions/ncc-2022/adopted/housing-provisions/5-masonry/part-56-masonry-components-and-accessories (verified 2026-05-08).
- Australian Building Codes Board, ABCB Housing Provisions Standard 2022, Part 5.7 Weatherproofing of masonry. https://ncc.abcb.gov.au/editions/ncc-2022/adopted/housing-provisions/5-masonry/part-57-weatherproofing-masonry (verified 2026-05-08).
- NSW Building Commission, Damp proof courses and flashing installation in masonry construction. https://www.nsw.gov.au/departments-and-agencies/building-commission/tradespeople-and-certifiers/damp-proof-courses-and-flashing-installation-masonry-construction (verified 2026-05-08).
- NSW Building Commission, Building Commission NSW visits 850 sites as part of unprecedented statewide inspection campaign. https://www.nsw.gov.au/departments-and-agencies/building-commission/news/building-commission-nsw-visits-850-sites-as-part-of-unprecedented-statewide-inspection-campaign (verified 2026-05-08).
Related
- NCC 2022 Volume Two, the residential building code that calls up AS 3700 and AS 4773 under H1D5 Structure
- Brickie (trade), what a bricklayer covers, licensing, tolerances, and what to require in their quote
- NCC structure, BCA and PCA, how the structural performance requirements sit within the NCC framework
- AS 1684 residential timber-framed construction, the timber framing standard that sits alongside AS 3700 on the same residential build
- Articulation joint, the vertical movement control joint required by AS 3700 and Housing Provisions 5.6.8
- Damp-proof course, the moisture barrier in masonry that must be installed per AS/NZS 2904 and Housing Provisions 5.7
See also
- Weep hole, open perpend above DPC that drains the cavity
- Perpend, the vertical mortar joint between bricks
- Brick gauge, course height measurement used to set out brickwork
- Cavity masonry, double-leaf masonry with a clear cavity between leaves
- Masonry veneer, single masonry leaf tied to a structural backing frame
- Deemed-to-satisfy, the NCC compliance pathway AS 3700 and AS 4773 satisfy
Last updated: 2026-05-08. Verified: 2026-05-08. Quarterly review for currency: confirm AS 3700:2018 is still current edition at Standards Australia and check NCC adoption status in each state.