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Choosing the wrong base coat render is one of the most avoidable — and most expensive — mistakes in the render application process. A product applied to the wrong substrate may look fine for weeks or even months before adhesion failure, cracking, or delamination makes the problem visible. By that point, the remediation cost is significantly higher than the cost of getting the specification right in the first place.
Unitex manufactures nine base coat render products, each formulated for specific applications. This guide maps the Unitex render range to common substrate types so builders and applicators can confirm the right product before ordering — and save the remediation conversation for someone else’s project.
Why Substrate Matching Matters
Render does not bond to every surface the same way. The porosity, surface energy, and texture of a substrate directly affect how a render cures, how well it adheres, and how it performs over time. A render formulated for high-porosity brickwork behaves differently on a low-porosity dense concrete surface. A render designed for EPS cladding has different polymer chemistry requirements than one intended for masonry.
Unitex formulates each render product with specific substrate requirements in mind. Using the wrong product — or the right product without the correct preparation — reduces adhesion, compromises weather resistance, and increases the risk of surface cracking. The substrate-matching process is not optional: it is the foundation of any properly specified render system.
What follows is a product-by-product breakdown organised by substrate type. For detailed preparation requirements, mixing instructions, and application specifications, always refer to the relevant Unitex System Specification guide and Application Manual.
EPS Cladding (Unitex Base Board System)
If you are working on the Unitex Base Board cladding system, one product applies and it is non-negotiable.
Base Board Render BBR 8.5 is the specified base coat render for the Unitex Base Board System. It is a cement-based, polymer-modified render developed specifically for application over factory-coated EPS panels. BBR 8.5 can be applied in a single pass at thicknesses of 6–16mm, achieving the render build required for BAL-rated compliance (BAL 19.5, BAL 29, and BAL 40) when used at the specified thickness within the complete Base Board System.
Why BBR 8.5 specifically? Because it is the only render independently tested and accredited as part of the CodeMark-certified Base Board System assembly. Substituting a different base coat render over the Base Board panels — even a high-quality polymer render — removes the system from its CodeMark accreditation. If you are specifying the Base Board System for compliance reasons (which is likely, given that CodeMark certification is usually the reason builders choose it), the render is not a variable. BBR 8.5 is the specified product. Use it.
Substrate preparation: BBR 8.5 is applied over factory-coated, applicator-prepared Uni-Base Board panels. It is NOT suitable for direct application over bare (uncoated) EPS boards. Refer to the Base Board Application Manual for the full preparation and application sequence.
Raw Polystyrene (Uncoated EPS)
For projects using raw, uncoated EPS boards (such as the Uni-IB Board), the render selection differs from the factory-coated Base Board system.
Polymer Render Wet applied directly to prepared raw EPS, or an appropriate primer-sealer combination, may be used depending on the system configuration. Confirm the correct product and preparation sequence with the Unitex technical team before specifying for raw EPS — the substrate surface and system context affect the appropriate choice.
Do not apply BBR 8.5 to bare, uncoated EPS. The product data sheet is explicit on this point. The factory-applied coating on Uni-Base Board panels provides the keyed surface that BBR 8.5 is designed to bond to.
Clean Brickwork
Clean brickwork — unpainted, uncontaminated, with well-defined mortar joints — is one of the most common render substrates in Australian residential construction.
HiLite Render™ is a strong general-purpose choice for clean brickwork, offering excellent workability and adhesion across a range of brick types and mortar joint profiles. Polymer Render Wet is also compatible with clean brickwork and is useful where a ready-to-use formulation is preferred over a powder product.
For projects with fire performance requirements applying to the render layer, Fast-R Render Non-Combustible and Redi Render™ Non-Combustible are the appropriate products — both carry AS 1530.1 non-combustible certification.
Substrate preparation: Brickwork must be clean, dry, and free of efflorescence, dust, laitance, grease, and organic matter. Depending on the porosity of the brickwork, Unitex Uni-Substrate Sealer may be required to equalise suction before render application. Refer to the System Specifications — Clean Brickwork guide for preparation requirements.
Deeply Raked Brickwork
Deeply raked brickwork — where mortar joints have been raked back to create a recessed profile — requires a render with good build and gap-filling capacity to achieve a flat, even surface.
HiLite Render™ performs well on raked brickwork given its workability and adhesion characteristics. Polymer Render Wet is also suitable. For non-combustible requirements, Fast-R Render or Redi Render apply.
Surface preparation is particularly important with deeply raked brickwork — ensure all loose mortar and debris is removed from the raked joints before render application. Refer to System Specifications — Deeply Raked Brickwork.
Painted Brickwork
Painted brickwork presents additional adhesion challenges because the paint layer creates a low-porosity, potentially unstable interface between the brick and the render. Adhesion depends entirely on the condition and integrity of the existing paint.
Polymer Render Wet is the appropriate product for painted brickwork where the paint is well-bonded, clean, and mechanically sound. If the paint is flaking, soft, or otherwise compromised, the paint must be removed or the surface mechanically prepared before rendering. Applying render over a compromised paint surface will result in failure regardless of the render product used.
Refer to System Specifications — Painted Brickwork for the full preparation assessment and application requirements.
AAC Panels
Autoclaved aerated concrete (AAC) panels — including products like Hebel — are lightweight and increasingly common in residential construction as an alternative to conventional masonry. They are highly porous and require specific preparation to achieve consistent render adhesion.
HiLite Render™ and Harbour Fine™ Non-Combustible are well-suited to AAC panels. The high porosity of AAC means suction management is critical — Unitex Uni-Substrate Sealer is typically required before render application to prevent the render from drying too quickly and losing adhesion.
Refer to System Specifications — AAC Panels for the preparation and application sequence.
Concrete Blockwork
Dense concrete blockwork has low porosity, which reduces render adhesion if the surface is not correctly prepared. A bonding agent or substrate sealer is typically required before render application.
HiLite Render™ with Unitex Cembond Substrate Sealer is the recommended approach for concrete blockwork. Cembond consolidates the surface and provides a consistent keyed interface for the render. Polymer Render Wet is also an option with appropriate preparation.
For fire-rated applications involving concrete blockwork — including Panel Patch for repair of fire-rated wall assemblies — Panel Patch (4hr Fire Rating) is available for patching and penetration fill where maintaining the fire rating of the assembly is a requirement.
Refer to System Specifications — Concrete Blockwork.
Fibre Cement Sheeting
Fibre cement sheeting (including products like James Hardie) is a common substrate for lightweight construction and renovation projects. It has moderate porosity and a relatively smooth surface that requires appropriate preparation for consistent render adhesion.
Aero Render, HiLite Render™, or Polymer Render Wet are appropriate for fibre cement sheeting with correct preparation. Unitex Uni-Substrate Sealer may be required depending on the condition and porosity of the sheeting surface.
Refer to System Specifications — Fibre Cement Sheeting for preparation and application requirements.
Coastal and High-Exposure Environments
For projects in coastal locations, high-humidity environments, or sites with elevated exposure to salt air and wind-driven moisture, Beach Render Non-Combustible is specifically formulated for these conditions. Its non-combustible certification to AS 1530.1 also makes it appropriate where fire performance requirements apply.
The render layer alone does not make a facade coastal-proof — correct substrate preparation, complete system specification (including appropriate texture finish and protective topcoat), and quality installation are all required. But starting with the right render product for the exposure environment is an important first step.
A Simple Decision Rule
If the substrate is the Unitex Base Board System — use BBR 8.5. No other render is appropriate within the CodeMark-accredited assembly.
For all other substrates, the decision comes down to three questions: What is the substrate type and condition? Are there fire performance requirements applying to the render layer? Is the environment high-exposure (coastal, humid, cyclically wet)?
Match the substrate to the product using the System Specification guides, apply the correct preparation sequence, and use the Unitex technical team as a resource when the project is non-standard. That process reliably produces the right answer — and reliably avoids the expensive one.
Browse the full Unitex base coat render range: https://www.unitex.com.au/product-category/base-coat-renders/
Questions about your project: Call 1800 RENDER (1800 736 337) or email sales@unitex.com.au
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