Materials Required for Rendering onto ICF

What is ICF?

ICF (Insulating Concrete Form) are hollow foam blocks that are stacked into shape, reinforced with rebar steel and then filled with concrete. The ICF blocks combine the thermal capabilities of EPS insulation with the strength of concrete and rebar steel, creating airtight, energy efficient and outstandingly structurally stable walls.

Unlike external wall insulation, when it comes to ICF blocks the insulation is already part of the substrate. However, the exterior polystyrene is not weatherproof and therefore needs finishing with a coloured render system.

Installing a coloured render system is a process of many stages, so we’ve put together a shopping list so that you know exactly what you need!

Priming the substrate:

Skip the primer – ICF is a foam insulation and therefore does not been priming

Applying the Beading:

We have a broad range or render beads that should be selected and applied as necessary to strengthen the substrate. The required beads will depend on the property:

Applying the Basecoat:

For render-only systems, we recommend using the EWI-225 Premium Basecoat. This is our strongest and most durable basecoat.

Coverage rates:

1x25kg bag covers 4.5m2

Drying times:

24-48 hours

Embedding the Mesh:

Fibreglass Mesh is embedded within the basecoat for extra reinforcement. This will ensure the system remains crack resistant.

Coverage rates:

1x50m2 roll covers 42.5m2 when overlapped

Priming the Basecoat:

A render primer should be used to increase the adhesion of the render to the basecoat. The type of primer will depend on the type of render you are using. For a Silicone Silicate system, we recommend using the SiSi Render Primer.


1x7L bucket covers 20m2

1x21L bucket covers 60-70m2

Drying times:

12-24 hours

Applying the render topcoat:

Once the primer is dry, the render topcoat can be applied. We recommend using either the Silicone Silicate Render or the Silicone Render.


1.0mm grain size: 1x25kg bucket covers c. 10m2

1.5mm grain size: 1x25kg bucket covers c. 7-10m2

Drying times:

24 hours (+)



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