Bricks: clay and concrete

TL;DR

The standard Australian residential brick is 230x110x76 mm work size; each course plus a 10 mm mortar joint stacks to 86 mm. Choose the right exposure grade for the location (Protected, General Purpose or Exposure per AS/NZS 4455.1:2008) and the right mortar (Protected: 1:2:9, Exposure: 1:0.5:4.5 cement:lime:sand per NCC 2022 Table 5.6.3). Clay bricks expand slightly after laying; concrete bricks shrink. That difference drives control joint placement. Miss a DPC or weep holes, and you will pay for rising damp or water ingress long after handover.

What it is

A fired or manufactured masonry unit, 230x110x76 mm work size (AS/NZS 4455.1:2008), laid in mortar to form walls, piers, and lintels. Two main types for residential work:

Clay bricks (also called face bricks, commons, or clay masonry units): formed from clay or shale, kiln-fired. Colour and texture come from the raw material and firing process.
Concrete bricks (also called concrete masonry units or CMU): cement, aggregate and water, vibrated and cured. Colour added via pigment or aggregate.

Both types are governed by AS 3700:2018, Masonry Structures (Fifth Edition, verified 2026-05-08). Product performance testing follows AS/NZS 4456:2003, Masonry units and segmental pavers — Methods of test (verified 2026-05-08).

Properties

Property	Clay brick	Concrete brick
Work size (standard)	230x110x76 mm	230x110x76 mm
Nominal course height (brick + joint)	86 mm (76 mm brick + 10 mm mortar)	86 mm
Moisture movement	Slight long-term expansion after firing	Net shrinkage over time (moisture loss + carbonation)
Colour stability	Colour fired in; does not fade	Surface colour; can lighten over years
Compressive strength (declared by manufacturer)	Widely varies: faces often 20-70 MPa	Widely varies: structural grades 15 MPa+
Thermal mass	High; suitable for passive solar design	Moderate to high
Salt attack resistance	Tested per AS/NZS 4456.10	Tested per AS/NZS 4456.10

The moisture movement difference between clay and concrete is the critical practical distinction. Clay units expand slightly after manufacture; concrete units shrink as they dry and carbonate. Build movement joints (articulation joints) to suit the material type. For clay, articulation joints at max 6 m centres; for concrete, closer spacing may be needed. Follow AS 3700:2018 and the manufacturer’s specification.

Grades and variants

Durability grades (AS/NZS 4455.1:2008)

Grade	Where to use
Exposure (Exp)	All locations including severe conditions: within approximately 1 km of a coastline, aggressive soils, saline water, below ground level, below DPC in wet sites. Highest durability per AS/NZS 4456.10 salt attack test.
General Purpose (GP)	All locations except where Exposure grade is required. Typical above-DPC internal and external residential work.
Protected (P)	Walls above DPC where the top of the wall is sheltered (by roof, eaves, coping, or similar). Not suitable for external exposure without shelter.

Source: AS/NZS 4455.1:2008 durability classification definitions (verified 2026-05-08).

Bond patterns

Pattern	Description	Typical use
Stretcher bond	Bricks laid lengthwise; each vertical joint offset by half a brick.	Cavity walls and masonry veneer (single-leaf). Most common in modern residential.
English bond	Alternating courses of headers (bricks laid end-on) and stretchers.	Solid masonry and heritage solid walls.
Flemish bond	Alternating header and stretcher in each course, staggered row to row.	Feature walls and heritage detailing.
Stack bond	All joints aligned vertically.	Feature work and internal non-load-bearing partitions only. Structurally weak unless reinforced.

Where to use

External walls: cavity masonry or masonry veneer over a frame
Internal load-bearing walls (solid masonry or cavity)
Feature and internal partition walls
Retaining walls (check structural engineer for heights above 1 m in most states)
Garden walls, piers, planters (Exposure grade and appropriate coping for exposed tops)

Where NOT to use

Stack bond as a structural wall without engineering design and bed joint reinforcement
Protected-grade bricks below DPC, in ground, or in exposed coastal sites (use Exposure grade)
Concrete bricks in expansion-joint layouts designed for clay: movement characteristics differ
Brick in contact with incompatible mortar (see Mortar section): over-strong mortar causes spalling, not the bricks

Mortar

Mortar mixes by exposure class

Per NCC 2022 Housing Provisions Table 5.6.3 (cement:lime:sand by volume) (verified 2026-05-08):

Exposure class	Mix (cement:lime:sand)
Protected	1:2:9
General Purpose	1:1:6
Exposure	1:0.5:4.5

Mortar must comply with AS 3700:2018 or AS 4773. Use the correct grade for the exposure class of the bricks. Over-strength mortar (too much cement) is a common error: it is stiffer than the brick, locks in movement stress, and causes cracking or spalling. Mortar is designed to be slightly sacrificial — it cracks before the brick.

Joint profile and finish

Standard joints are 10 mm. Flush, weathered (raked and tooled), and ironed (rodded) profiles all perform well. Raked joints cut deep into the bed remove mortar cover from the brick and increase water ingress risk — avoid on exposed external walls unless the brick manufacturer specifies otherwise.

Cavity masonry and masonry veneer

Two main construction methods for residential external walls:

Masonry veneer (single brick leaf over frame)

A single skin of brickwork tied to a timber or steel frame with wall ties. The frame is the structural element; the masonry is cladding only.

Cavity between brick and frame: minimum 25 mm clear per NCC 2022 Part 5.2 (ties must be fitted) (verified 2026-05-08)
Tie type: light duty ties for wind speed N2 and below; medium duty for N3+ per NCC 2022 Table 5.6.5a (verified 2026-05-08)
Maximum height: 8.5 m above adjacent finished ground level (NCC 2022 Part 5.2.2) (verified 2026-05-08)
DPC and flashing required at base: see Weatherproofing section

Cavity masonry (double leaf)

Two leaves of brickwork separated by a cavity, both structural.

Cavity width: not less than 35 mm and not more than 75 mm per NCC 2022 Part 5.3.3(3)(a) (verified 2026-05-08)
Minimum leaf thickness: 90 mm each (NCC 2022 Part 5.3.3(2)) (verified 2026-05-08)
Maximum wall height: 8.5 m above adjacent finished ground level (NCC 2022 Part 5.3.2) (verified 2026-05-08)
Tie spacing (medium duty Type A, aligned joints): max 300 mm vertical, max 450 mm horizontal per NCC 2022 (verified 2026-05-08)

See cavity masonry and masonry veneer glossary entries for definitions.

Weatherproofing

Damp-proof course (DPC)

DPC position requirements per NCC 2022 Part 5.7.4 (verified 2026-05-08):

Site condition	DPC minimum height above adjacent surface
Standard	150 mm above finished ground level
Adjacent sloped paved/concreted area	75 mm above finished surface
Protected area (carport, verandah)	50 mm above finished surface
Low rainfall, weather-protected	May be as little as 15 mm

See damp-proof course glossary entry.

Weep holes

Open perpend joints (weep holes) must be installed in the course immediately above any flashing or DPC per NCC 2022 Part 5.7.5 (verified 2026-05-08):

Minimum height: 50 mm (height of a standard perpend joint)
Maximum spacing: 1.2 m centres

Not required below sill flashings over openings less than 1.2 m wide. See weep-hole and perpend glossary entries.

Flashing

Sill and head flashings per NCC 2022 Part 5.7.4(3) must (verified 2026-05-08):

Extend not less than 150 mm beyond reveals on each side of the opening
Be embedded not less than 30 mm into the masonry leaf
Turn upward not less than 150 mm at the back of the cavity at head positions

See flashing glossary entry.

Articulation joints

Articulation joints (movement joints) per NCC 2022 Part 5.6.8 (verified 2026-05-08):

Minimum width: 10 mm
Maximum spacing: 6 m centres in straight walls without large openings
Maximum spacing: 5 m centres where openings exceed 900x900 mm

Joint filler and sealant must be installed per the manufacturer’s specification. For clay masonry, sealant must accommodate the slight long-term expansion of fired clay. See articulation-joint glossary entry.

Fixing and installation

Setting out

A brick gauge rod is essential for setting out. Standard modular coursing: 1 course = 86 mm (76 mm brick + 10 mm joint). Common set-outs:

Courses	Height
1	86 mm
5	430 mm
10	860 mm
15	1290 mm
20	1720 mm
30	2580 mm

Window sills and door heads align to brick course heights wherever possible. Design up from finished floor level (FFL) or DPC height, not down from roof.

See brick-gauge glossary entry for the setting-out tool.

Mortar bedding

Full bed joint: mortar applied across the full width of the brick for structural work
Furrowed bed joint: mortar furrowed down the centre to improve initial suction and bedding; not a substitute for full mortar coverage in exposure applications
Perpend (cross) joints: fully flushed up. Perpends with missing mortar (snots only) are a waterproofing failure point in external walls

Snots and voids

Mortar snots (droppings) that fall into a cavity are a known cause of water bridging across a cavity. Clean the cavity base as work progresses — attach hessian or similar to the ties at each lift to catch droppings, remove before enclosing. See snots glossary entry.

Tolerances and acceptance

Numerical

Item	Limit	Source
Brickwork plumb	Per current HIA Guide to Materials and Workmanship and the relevant state Guide to Standards and Tolerances. Verified numerical value pending HIA member access. [HIA-061]	HIA Guide / state guide
Mortar joint width variation from nominal	Per current HIA Guide to Materials and Workmanship. Verified numerical value pending HIA member access. [HIA-062]	HIA Guide / state guide
Face alignment of brickwork (horizontal course straightness)	Per current HIA Guide to Materials and Workmanship. Verified numerical value pending HIA member access. [HIA-063]	HIA Guide / state guide

Visual acceptance at PCI

Joints fully filled: no voids in perpend or bed joints visible from external face
Joint profile consistent: same profile (weathered, flush, ironed) throughout; no mix of profiles
No efflorescence at handover (see What can go wrong)
Ties not visible through face
Weep holes open and clear
Articulation joints sealed and undamaged
DPC visible at base, not buried under backfill or paving
Cavity clear of debris

Working with other trades

Engineer / designer: structural masonry above two storeys, retaining walls over 1 m, non-standard wind class or site classification — get an engineer’s specification before the brickie starts
Carpenter (chippy): frame must be plumb, square, and straight before masonry veneer starts; a racked frame is not fixable after brickwork is up
Waterproofer / plumber: wet area penetrations through external brickwork need flashing and sealing before internal linings go in
Sparky: conduit penetrations through brickwork need sealing post-installation
Concretor / earthworks: slab edge or footings must be formed to allow for correct DPC height; DPC too low means moisture ingress, DPC too high means it gets buried

Health and safety

Manual handling: a standard clay brick is 2.7 to 3.5 kg. Bricklaying is repetitive motion at pace — cumulative load is high. Use correct lift technique and brick tongs where available
Silica dust: cutting, grinding, or sawing bricks generates respirable crystalline silica (RCS). The Australian workplace exposure standard is 0.05 mg/m3 (8-hour TWA) (Safe Work Australia) (verified 2026-05-08). Wet-cut or use local exhaust ventilation. P2 respirator minimum
Masonry walls during construction: unsupported or partially-braced masonry walls are a collapse risk in wind events. Refer to Safe Work NSW guidance on masonry wall safety during construction
Mortar: cement is caustic; prolonged skin contact causes chemical burns. Waterproof gloves when mixing and laying. Eye protection mandatory
Struck-by hazard: brick falls from scaffold or elevated formwork. Keep the drop zone clear, use toe boards on scaffold

Suppliers

Major clay brick brands in Australia:

Boral (boral.com.au): Austral Bricks; largest distribution network
PGH Bricks (pghbricks.com.au): part of CSR; wide range of face bricks
Brickworks (brickworks.com.au): multi-brand including Daniel Robertson, Bowral Bricks, Nubrik

Major concrete brick brands:

Adbri Masonry (adbrimasonry.com.au): concrete bricks and blocks
National Masonry (nationalmasonry.com.au): concrete and AAC masonry units

Industry body: Think Brick Australia — free technical manuals including TBA 10 (Construction Guidelines) and TBA 09 (Detailing) (verified 2026-05-08).

[Sponsor / preferred supplier slot. ACCC disclosure required.]

What can go wrong

Wrong exposure grade: Protected-grade bricks in a coastal or below-DPC application spall and salt-attack within years. Match the grade to the site
Over-strong mortar: a mortar mix stronger than the brick locks in movement stress and causes brick face spalling. Use the correct mix per NCC 2022 Table 5.6.3
Missing or buried DPC: rising damp is expensive to rectify post-handover; DPC must be visible at base of brickwork, 150 mm above finished ground
Blocked or absent weep holes: water that enters the cavity has nowhere to drain; wall saturation follows
Mortar snots bridging the cavity: directs water across the cavity to the internal leaf, causing water ingress that looks like a roof leak
Articulation joints omitted or undersized: differential movement between clay (expansion) or concrete (shrinkage) and the structure cracks the brickwork face; repairs are cosmetic at best
Efflorescence: soluble salts migrate to the surface and deposit as white staining. Caused by water passing through the brickwork, usually from a weather exposure problem (missing DPC, blocked weep holes, no coping on top of piers). Treat the source, not the symptom
Stack bond without reinforcement: structurally weak; do not use on external or load-bearing walls without engineering design and bed joint reinforcement
Wrong tie or spacing for wind class: light duty ties in a high-wind area fail in a storm; check NCC 2022 Table 5.6.5a against the site wind classification

References

AS/NZS 4455.1:2008, Masonry units, pavers, flags and segmental retaining wall units — Masonry units (Standards Australia) (verified 2026-05-08)
AS/NZS 4456:2003 (set), Masonry units and segmental pavers — Methods of test (Standards Australia) (verified 2026-05-08)
AS 3700:2018, Masonry Structures (Standards Australia) — Fifth Edition, current (verified 2026-05-08)
NCC 2022 Housing Provisions Part 5, Masonry (ABCB) (verified 2026-05-08)
NCC 2022 Housing Provisions Part 5.7, Weatherproofing of masonry (ABCB) (verified 2026-05-08)
Think Brick Australia, TBA 10: Construction Guidelines for Clay Masonry (thinkbrick.com.au) (verified 2026-05-08)
Safe Work Australia, Workplace exposure standard for respirable crystalline silica (safeworkaustralia.gov.au) (verified 2026-05-08)