Raw polystyrene — expanded polystyrene (EPS) installed as external cladding without a factory-applied coating — is not a finished wall system on its own. It needs a mesh-reinforced render build-up to become weatherproof, impact-resistant, and ready for a decorative finish, and getting that build-up right is what turns a lightweight insulation product into a compliant, durable external wall.
The Unitex Coating System for Raw Polystyrene
Unitex Base Board Render is applied directly to the raw polystyrene surface, with Unitex external angles used at corners and edges where required. While the render coat is still wet, Unitex alkaline-resistant fibreglass mesh is embedded across the entire surface — a step that has to happen within the coat’s working time, not as a separate later stage, since the mesh needs full embedment in uncured render to bond properly and provide the impact and crack resistance the finished system depends on.
Why the Mesh Step Isn’t Optional
Polystyrene alone offers no impact resistance and no weatherproofing — it’s an insulation material, not a cladding material, until it’s coated. The embedded fibreglass mesh is what gives the finished wall its resistance to knocks, movement, and surface cracking, and skipping or rushing this step is one of the more common ways EPS cladding installations fail early. Builders working with trades unfamiliar with EPS-specific render systems should confirm this sequencing is understood before work starts on site.
From Insulation Board to Finished Facade
Once the base coat and mesh layer have cured, raw polystyrene cladding follows the same path as Unitex’s factory-coated Base Board panels — ready for a texture and finish coat from the full Unitex range, and covered by the same accreditation and warranty framework that applies across the render system. The difference is simply where the first coat is applied: on Base Board panels it happens at the Dandenong factory, while on raw polystyrene it happens on site, which places more responsibility on correct application technique and timing.
Full Technical Specification
Complete application detail — coverage rates, coating thickness, and drying times for the base coat and mesh embedment stage — is available on the Uni IB Board Coating Specifications page.
Get the System Right on Site
For raw polystyrene cladding projects anywhere in Australia, the Unitex technical sales team can confirm application requirements, review project plans, and provide a full quotation. Call 1800 RENDER, request a quote online, or view the full Cladding range to compare against the factory-coated Base Board system.
