A Comprehensive guide to EWI Pro Silicone Renders

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Silicone render is the finishing element or the final coat of a thin coat render or external wall insulation system. This finishing coat is both textured and tinted to any colour, providing an almost endless combination of finishes.

The silicone render is ready to apply straight out of the bucket – you don’t need to add any water or any other additives, and once dried on the wall, it provides a robust finish to the system for years to come.

The silicone render finish is also ‘cement free’, which makes it highly elastic – so no cracking.

Silicone renders have been within the EWI Pro suite of products for a number of years. Our first thin coat system was the mineral render system, and while still a good alternative to silicones, it didn’t have all apparent installer advantages. Mineral render is just as breathable as the silicone render but, to achieve a coloured finish it still requires painting. Also, the mineral render comes in a bag form, so you still need to add water to it to make it work.

We then produced our first synthetic render (which came in a bucket) and this was the ultimate game changer. While new to the UK, this product had been used across Europe for decades, and basically allowed the applicator to apply a protective layer of render, in any colour, in one application pass. This first synthetic render was the acrylic finish. It took us a further 5 years to start introducing the silicone renders into the armoury of products.

Silicone renders have two major advantages over acrylic render – they are breathable and hydrophobic – so repel water. Breathability is key, especially here in the UK, where properties often have damp solid brick walls – the silicone renders allow any trapped water to dissipate. The acrylic renders are limited for this reason and are much better suited for dry, warmer climates.

So what we have done is taken the silicone render – with its breathable and hydrophobic properties and developed new specific silicone renders to cater for different requirements and in the following sections we look in to these different silicone renders in a bit more details.

Fibreglass Mesh is an integral component for both EWI and Render-Only systems. The mesh is embedded with the cement-based basecoat layer ensuring that the system is both strong but also flexible to allow for natural building movements.

We stock Fibreglass Mesh in both 1m2 and 50m2 rolls.

If you are unsure about any of the products that we stock, or if you would like any further information, do not hesitate to contact our friendly sales team who will be more than happy to answer any questions you may have!

 Utilising Beading and Mesh is crucial in order to reinforce weak points within your structure, as this prevents cracking of render finishes and stops water ingress behind the system. 

Expanded polystyrene EPS insulation board is a high-performing thermal insulation at the centre of our external wall insulation systems. It significantly upgrades the thermal properties of a building, improving U-values, and reducing the risk of water penetration and condensation. EPS boards are compatible with timber, masonry and system-built properties, as well as tile hanging and a wide range of rendering systems. EPS has been designed specifically to be applied onto masonry or timber-backed walls using adhesive and mechanical fixings. They can also be installed in the cavity void if the property is being insulated using cavity wall insulation.

EPS insulation is the most popular material used in external wall insulation systems. One of the stand-out benefits of using EPS for your project is that it’s great value for money. In this way, choosing a cost-effective insulation board means that you can cut down on cost without sacrificing quality or thermal performance.

When installing EPS as part of an EWI system, applicators will also find that the materials required for the installation are available at a much lower cost. This is because EPS is extremely lightweight, so the required adhesive is of a much lower strength and the fixings are plastic rather than metal. EPS is also a non-breathable material and so lower-cost thin coat renders can be used in combination. For example, with the EWI-075 Silicone Render or EWI-040 Acrylic Render.

• Composition: expanded polystyrene, graphite
• Thermal Conductivity: 0.032W/(m2K)
• Reaction to Fire: Class E
• Compressive strength: 70kPa
• R-value: 1.97W/(m2K)
• Weight: 13.02kg
• Weight/m2: 1.13kg
• Size of boards: 1200 x 600mm
• Thicknesses available: 20mm, 30mm, 50mm, 70mm, 90mm, 100mm, 150mm and 200mm
• Coverage in pack: 0.72m2
• Bending strength: >= 75kPa

Use netting on scaffolding to reduce the amount of polystyrene blowing about in the wind. We highly recommend that you try to use a hot knife or hot wire cutters to minimise the number of polystyrene offcuts. However, you can still use a standard knife should you choose. Ideally, you should cut the EPS insulation boards within a covered area as this reduces offcuts blowing around.

EPS insulation boards should always be installed in accordance with the manufacturer’s installation guidelines. This should cover design and all aspects of the application of the insulation. Initially, you can fix the EPS boards to the substrate (masonry or timber) by a mortar/adhesive or simply by mechanical fixings.

After fixing the board to an external wall, we recommend that you cover the boards with an outer layer. This can be either be the mortar basecoat or simply a netting covering to protect from excessive heat, moisture and UV exposure.

Before you apply the basecoat or mortar for the fibreglass mesh, you should rasp or sand down the top surface of the board to produce an abrasive surface. Once you’ve done this, the substrate is ready for the application of the fibreglass mesh. For further information, please download the full installation guide.