ICF Help & Advice

Our insulated concrete formwork help & advice centre has been created as a reference and information hub for designing and building ICF structures in general, and Polarwall in particular.

ICF Claddings & Finishes

A render finish is one of the more popular options for cladding on ICF walls.  The type of render system that Polarwall recommends is a modern two coat render finish.  The render is made-up of a cementitious adhesive basecoat into which a reinforcing mesh (of either alkaline resistant fibreglass mesh or a polypropylene mesh) is trowelled.  Once the base coat has set, the through-coloured top coat is applied.  

Of these modern render systems there are two versions available. One is an acrylic based  render and the other is a silicone based render. The silicone render has a couple of advantages in that it sheds moisture and dirt much more efficiently. It is also a flexible material than the acrylic based render. This flexibility is important, due to material expansion and contraction as temperatures change.. 

As with any building material there are good render systems and not so good render systems.  Dont be fooled by cost alone. A good render can be placed much thinner than a render using cheaper ingredients.  

Traditional cementitious renders are not recommended for use on ICF. This is because cementitious renders shrink and move far more than the XPS material.   

Our recommended render for ICF walls

A render product that is very popular with some of our builders is the Parex render system. This uses their Maite base coat and their Siloxine through-coloured silicone top coat. 

The textured surface on the Polarwall XPS insulation boards is specifically designed to bond to concrete and cementitious products.  In a recent test using the Parex Maite basecoat, the pull off strength of the render was 50% greater than the same basecoat tested on expanded polystyrene. 

The bond strength was equivalent to a pull off strength of 38 tonnes per square metre. 

For other options on cladding your ICF wall see our help article about Timber Cladding on ICF, and our page on brick slips.


The various sections above cover the main topics for ICF construction both above and below ground. 

Do not use this as an alternative to what your chosen manufacturer recommends.  We can do things with Polarwall that ICF blocks can’t do and there may some things that you do with other ICFs that Polarwall can’t do. For example our instructions on vibrating the concrete may not be wise on some EPS block systems. 

We want to add to and develop this section, so we welcome all your questions, suggestions for topics and feedback.  If you want to go deeper into a topic please let us know.  This advice hub does not replace our training (or any other companies training) and you still need to avail yourself of our FREE training course.

Have a question or suggestion not listed here? Feel free to contact us