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Applying Coloured Render 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.

Here at EWI Store, we use EPS insulation in our external wall insulation systems as a means of retrofitting thermal insulation to a property in order to upgrade its thermal performance. With 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. In this blog, we’re going to talk about how you can apply coloured render onto ICF.

How to apply Coloured Render onto ICF substrates

The method of application of coloured render onto an ICF substrate is very similar to applying coloured render to EPS insulation boards. First the basecoat must be applied to the substrate using a trowel to create a smooth surface before the thin coat render can be applied. To create the basecoat, you can use either the EWI-220 EPS Basecoat Adhesive, or the EWI-225 Premium Adhesive for an extra strong and stable base.

Fibreglass mesh needs to be embedded within the basecoat layer in order to enhance tensile strength and crack-resistance. Once this is done, the basecoat needs to be as smooth as possible because any major imperfections will be visible due to the fact that the render itself is applied in such a thin layer.

The basecoat layer needs to set for a period of 24-48 hours before any more work can be done. After it’s set, a render can be applied; this will depend upon the type of coloured render that you intend to use. For example, our SiSi Render Primer is designed for use with our Silicone Silicate Renders. The primer needs to be left to set for 12 hours, and then finally the coloured render can be applied!

Contact our sales team for a copy of our full installation guide!

Why use Coloured Render on ICF

Coloured render can offer your property a world of benefits and is an excellent finish for ICF substrates. Coloured renders are flexible and crack-resistant because they are applied in such a thin layer (it can vary from 1mm-3mm thick depending upon the grain size you go for!). When choosing a coloured render, you can select from our expansive colour chart or we can custom mix the render into any shade, we also have a blog post ‘coloured render cost per m2’ which outlines really clearly how much the system typically costs. 

With EWI Store, we offer a wide selection of renders for a range of substrates:

Silicone/Silicone Silicate Render: Silicone-based renders are a high performance option when it comes to coloured render. Not only does Silicone Render possess self-cleaning capabilities (although silicone silicate less so), both are also highly breathable and hydrophobic, thereby preventing water vapour from becoming trapped within the substrate and the render system.

Acrylic Render: Acrylic is what most people think of when they think of thin coat coloured render. It is most renowned for coloured render because it is so great at holding onto colour pigment (think of the vibrancy of acrylic paint). Acrylic render is very impact resistant, so if you have kids who love kicking footballs against your walls acrylic render is right for you!

Mineral Render: Mineral render is a great choice if you live in a particularly harsh climate. Because of the fact that it’s fast drying, it can be installed in cold or humid conditions, nevertheless it does require painting with a silicone paint after it has dried to prevent the formation of lime bloom – which is essentially like a cement ‘disease’ which makes your house render appear patchy.

So there you have it. Our full range of renders and how they are applied to an ICF substrate. For any further questions, comment down below or call up our technical team who are always happy and on-hand to help.

Applying Render to a Range of Substrates:

Recap of Materials required for applying coloured render onto ICF:


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