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External render

IS 53N Spray Silicone Plaster
IS 53N Spray Silicone Render
5,0 (1 reviews)
Price range: £74.99 through £83.31 ex. VAT
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Tytan SISI IS55N Silicone Spray Render 25kg
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Mosaic Render Lakma 25kg
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QUARTZ RENDER
QUARTZ RENDER
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Thin coat silicone plaster TYNKSIL QS
Lakma Silicone Render Tynksil QS 25kg
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SPEED TYNK - plaster binding accelerator 250ml
Speed Tynk – Plaster Binding Accelerator 250ml
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Accelerator for Render and Paint 125ml
Accelerator for Render and Paint 125ml
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External render for EWI systems

External render is the final protective and decorative layer used on External Wall Insulation (EWI) systems. It protects insulation boards from weather, supports vapour diffusion, helps prevent cracking, and delivers a consistent facade finish.

EWI-system compatible
Weather-resistant finish
Breathable render options
Coloured, low-maintenance

What is external render for EWI?

EWI render is a thin-coat finishing render applied over insulation boards such as EPS or mineral wool. It is part of a complete render system, not a standalone product.

  • Protection: shields insulation from rain, frost and UV.
  • Breathability: supports controlled vapour diffusion to reduce trapped moisture risk.
  • Flexibility: helps resist cracking caused by movement and thermal cycling.
  • Finish: delivers stable colour and texture across the facade.

External render is typically applied over: basecoat adhesive, reinforcement mesh, and a primer matched to the top coat.

Where external render is used

  • Residential houses (new build and refurbishment).
  • Solid wall insulation upgrades on older properties.
  • Low-rise and multi-storey buildings (system dependent).
  • Brick, block or concrete substrates – when used with an EWI system.

Types of external render used in EWI systems

Recommended

Silicone render

  • Highly flexible and crack-resistant.
  • Very low water absorption with strong weather resistance.
  • High vapour permeability and low maintenance.

Acrylic render

  • Good flexibility for insulated facades.
  • Budget-friendly option for less demanding conditions.
  • Lower breathability than silicone.

Mineral render

  • Highly breathable cement-based finish.
  • Typically requires painting (system dependent).
  • Less flexible than polymer renders.

Quartz render (silicone-based)

  • Decorative render with quartz aggregate for enhanced durability.
  • Very high resistance to impact, dirt and weathering.
  • Available in silicone or acrylic base (silicone recommended for EWI).
  • Popular choice for modern external wall insulation systems.

Key technical properties

  • Crack resistance: designed for movement in insulated facades.
  • Breathability: supports vapour diffusion to reduce moisture build-up.
  • Weather resistance: protection against rain, frost and UV exposure.
  • Thin coat finish: typically matched to grain size (1.5-3.0 mm).
    Solid vs cavity – quick comparison

    1.5 mm (fine), 2.0 mm (standard), 3.0 mm (textured).

    Compatibility with EWI systems

    External render must be system-compatible. Mixing components from different systems can cause cracking, delamination, moisture issues, and loss of warranty.

    • Basecoat adhesive compatibility
    • Reinforcement mesh specification
    • Insulation type (EPS / mineral wool)
    • Primer matched to the top coat

    Cost factors for external render

    • Render type (silicone, acrylic, mineral)
    • Grain size and finish texture
    • System components and insulation specification
    • Surface area and facade detailing

    Maintenance and durability

    • Silicone renders usually need only occasional low-pressure washing.
    • Good resistance to dirt and algae build-up (product dependent).
    • Correct detailing around openings is critical for long-term performance.

    Frequently asked questions

    Is external render waterproof?

    It is water-resistant, not fully waterproof. It repels rain while allowing vapour to escape.

    Yes, but this page refers specifically to EWI render systems.

    Correctly installed systems with mesh reinforcement are designed to resist cracking.

    Yes. Most renders are available in a wide colour range with factory-pigmented finishes.

    Quick spec checklist

    1

    Choose render type: silicone (best), acrylic, or mineral.

    2

    Confirm compatibility: basecoat, mesh, primer, insulation.

    3

    Plan detailing: corners, beads, reveals, drip edges.

    Get the right EWI render

    Share your facade area and insulation type to estimate materials and select a compatible render system.

    Try our free EWI calculator
    Request a quote
    Typical system layers

    1

    Insulation boards

    2

    Basecoat adhesive

    3

    Reinforcement mesh

    4

    Primer

    5

    External render (top coat)