Two of the most frequently asked questions at Seymour Building Supplies cover the same broad territory: what’s involved in rendering brickwork properly, and what are the standard brick sizes used in Australian construction? Whether you’re a tradie quoting a job, a builder planning a project, or a homeowner tackling a significant DIY renovation, understanding both of these topics will save you time, money, and materials.
Here’s the practical guide from the team that has been supplying Sydney’s building community for decades.
Rendering Brickwork: What It Is and How to Get It Right
Render is a coating applied to masonry surfaces — typically brick, block, or concrete — to provide a smooth or textured finish, improve weatherproofing, and enhance the visual appearance of the structure. Done correctly, a well-applied render finish can transform the look of a building and provide decades of low-maintenance performance. Done poorly, it can crack, delaminate, or hold moisture in ways that cause long-term damage to the substrate.
Types of Render
Cement sand render — The most traditional and widely used render type. A mixture of cement, sand, and water applied in one or two coats, finishing to a smooth or textured surface. The mix ratio affects workability, strength, and flexibility — a rich mix with too much cement is more prone to shrinkage cracking. A typical ratio of one part cement to four or five parts washed coarse sand produces a balanced, workable render. Adding lime — a common 1:1:6 cement, lime, and sand mix, for example — improves workability and water retention, and reduces the risk of shrinkage cracking compared with a straight cement and sand mix.
Pre-bagged polymer-modified renders — Products like those from Sika, Drizoro, and Mapei (all stocked at Seymour Building Supplies) contain admixtures that improve adhesion, flexibility, and water resistance compared to basic cement sand mixes. They’re a consistent, reliable option for projects where performance and ease of application are priorities.
Acrylic render systems — A two-coat system using a fibre-reinforced base coat and a coloured acrylic texture coat. Acrylic systems offer excellent crack resistance and are available in a wide range of colours and textures. They’re particularly popular for feature walls and residential applications where the finish is a key part of the aesthetic outcome.
Lime render — Traditional lime-based renders are softer, more breathable, and more flexible than cement-based products. They’re particularly suited to heritage buildings and older masonry where compatibility with the existing substrate is important.
Surface Preparation: The Most Important Step
The most common cause of render failure is inadequate surface preparation. Before any render is applied, the substrate must be:
- Clean and free of dust, efflorescence, paint, oil, and loose material
- Sufficiently dampened (but not saturated) to prevent the dry substrate from drawing moisture out of the render too rapidly
- Keyed or treated with a bonding agent where the surface is too smooth to mechanically key the render
For highly absorbent surfaces — such as newly laid lightweight blockwork — a proprietary bonding agent significantly improves adhesion and reduces the risk of delamination. Choose the product to suit the exposure: SBR and acrylic-based bonding agents are formulated for external and wet-area work, whereas PVA-based products re-emulsify when they get wet and should be kept to internal applications only. If you’re unsure which is right for your substrate, ask our team.
Application Technique
Render is typically applied in one or two coats depending on the required thickness and finish. A scratch coat is often used as a first pass on rough or uneven surfaces, keyed while still green to provide mechanical bonding for the finish coat. Total render thickness is typically 10 to 20mm, built up in coats — a single coat much beyond 15mm is prone to slumping — and the finish coat is then brought to the desired surface texture.
Key points for successful rendering:
- Avoid rendering in direct hot sun or strong wind, which can cause the render to dry too quickly and crack
- Maintain consistent mix ratios throughout the job
- Scratch or key intermediate coats while still green
- Mist cure finished surfaces in hot or dry conditions to slow drying and prevent shrinkage cracking
Rendering Supplies at Seymour’s
Seymour Building Supplies stocks a comprehensive range of rendering materials and accessories, including:
- Boral, Sika, Mapei, and Drizoro cement and render products
- Washed sand and render aggregates in quantities from 30kg bags through to bulk delivery
- Mesh and fibreglass reinforcing for render systems
- Bonding agents and surface primers
- Angle beads, stop beads, and expansion joints
- Rendering tools including floats, hawks, and trowels from OX Tools and Sutton Tools
Standard Brick Sizes in Australia
Getting the brick specification right — and calculating quantities accurately — is fundamental to every bricklaying and rendering project. Here’s what you need to know about the brick sizes used in Australian construction.
The Standard Metric Brick
The most commonly used brick in Australian residential and commercial construction is the standard metric brick, with the following dimensions:
- Length: 230mm
- Width: 110mm
- Height: 76mm
Add a standard 10mm mortar joint and the coordinating unit size — the space the brick occupies in the wall — becomes 240mm x 120mm x 86mm. The 240mm and 86mm figures are the ones used for calculating quantities and setting out coursing. Note that the 120mm coordinating width allows for a 10mm collar or cavity joint; a finished single-skin wall is still 110mm thick.
How Many Bricks Per Square Metre?
At standard coordinating dimensions, a square metre of single-skin brickwork works out at 48 bricks (1 ÷ 0.240 ÷ 0.086), and most tradies round up to 50 as a working figure. For double-brick construction, the count doubles to approximately 100 bricks per square metre of completed wall. Always add 5 to 10% to your calculated quantity for waste, cuts, and breakages.
Other Common Brick Sizes in Australia
Beyond the standard metric brick, these are the formats you’ll come across most often:
- Utility (also sold as jumbo or long format) — 290mm x 90mm x 90mm. Fewer bricks and fewer mortar joints per square metre, which speeds up laying.
- Wide format — 290mm x 140mm x 90mm. Used where a thicker single-skin wall is required.
- Modular — 190mm x 90mm x 90mm. Sized to metric modular coordination.
Names like “jumbo” and “maxi” are used loosely across the industry, so always confirm the actual dimensions on the product spec sheet before ordering.
Matching Existing Brickwork
For renovation and extension projects, matching the existing brick is critical. Older Australian homes built before metrication — roughly, before the mid-1970s — used imperial bricks measuring around 228mm x 110mm x 73mm, though dimensions vary with the era and the manufacturer, so measure several bricks on site and take an average.
Imperial bricks are slightly smaller than the modern metric brick in every dimension. The height difference matters most: a few millimetres per course compounds quickly, and by the time you’ve laid ten courses the new and old brickwork no longer line up. That’s usually managed by sourcing a closely matched brick, adjusting mortar joint thickness across the junction, or setting the new work out so any discrepancy is taken up at a natural break in the wall.
Seymour Building Supplies’ experienced team can assist in identifying the right brick specification for your project, including advice on matching existing work and calculating quantities accurately.
To discuss your rendering or brickwork project and place an order, visit our Building Supplies page — including our Bricks & Blocks range — or call the team on (02) 9816 5999.
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