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Case Study – Silicone Render Internally

At EWI Pro, we specify many projects throughout the UK. They vary in size, scope, and system application. From large-scale commercial projects to small-scale residential, we cover every type of project. As we’ve discussed recently, we provide a comprehensive range of testing processes. These include wind-load tests, moisture testing, and pull-out tests. Our Technical Team also provides expert U-value calculations to ensure the system is suitable. In our new series of blogs, we will shine a light on specific projects and the build-ups they utilise.

Whilst Silicone Render is our most popular and versatile finish, it is often overlooked and underused for internal purposes. Contrary to popular belief, you can use silicone render internally to the same effect as using it externally. This case study focuses on a large commercial property renovated internally with a clean and professional finish. The choice of tint and grain size (1.5mm) contribute to the overall muted and refined finish.

Project details

– Substrate: Blockwork
– U-Value change: N/A
– Basecoat: N/A
– Finish: EWI-075 Silicone Render
– Colour: Pure White
– Location: London
– Installer: Scott

The build-up – Silicone Render Internally

The internal areas of the commercial property required a level and dimensionally stable substrate. As such, plasterboards and render carrier boards were installed. Following this, the regular process for installing a render coat was followed.

1. Preparation

Before you begin, make sure the render carrier board is clean, dry, and free of any contaminants. Dust, grease, or any loose particles can hinder the adhesion process.

2. Mixing the EWI-225 Premium Basecoat

Start by mixing the basecoat with water according to the manufacturer’s guidelines. It’s crucial to ensure that the consistency is even and lump-free.

Tools Required:

  • Mixing drill with paddle attachment (to ensure thorough mixing).
  • Measuring bucket or container for water.
3. Applying the EWI-225 Premium Basecoat

Using a hawk and trowel, apply the mixed EWI-225 Premium Basecoat onto the render carrier board. Aim for even and consistent coverage. Ensure the basecoat is applied at the recommended thickness. It will provide a solid foundation for the silicone render.

Tools Required:

  • Hawk (a flat tool used to hold the render).
  • Steel trowel (to apply and smooth out the render).
4. Allow to Dry

After applying the basecoat, allow it to dry thoroughly. The drying time will vary based on environmental conditions but typically it should be left for at least 24 hours.

5. Mixing the EWI-075 Silicone Render

Just as with the basecoat, mix the silicone render with water (or as per the manufacturer’s instructions). Ensure the mix is lump-free and has a consistent texture.

6. Applying the EWI-075 Silicone Render

Using a clean hawk and trowel, apply the silicone render over the dried basecoat. Ensure you achieve the desired thickness as per the product’s guidelines. Silicone renders are usually applied thinner than basecoats, so make sure not to apply too thick.

Tools Required:

  • Hawk.
  • Steel trowel.
7. Texturing the Surface

Once the EWI-075 Silicone Render is applied and before it starts setting, use a render float to achieve the desired texture on the surface. Whether you want a smooth finish or a more textured appearance, the render float will help you achieve that.

Tools Required:

  • Render float.
8. Curing and Drying

Allow the silicone render to cure and dry thoroughly. Again, drying time can vary, but typically you should wait at least 24 hours, or until the render is completely dry to the touch.

9. Final Touches

Inspect the rendered surface for any imperfections or inconsistencies. Any minor touch-ups can be done using a trowel or float.

Benefits of using silicone render internally

Silicone render, often chosen for its external application benefits, also offers several advantages when applied internally.

Moisture Resistance

One of the standout benefits of silicone render is its excellent resistance to moisture. Unlike some traditional materials, silicone render does not readily absorb water. This means that even in areas with higher humidity or potential for moisture exposure, such as bathrooms or kitchens, the render remains durable. This water-resistant property also aids in preventing mould growth, ensuring a healthier living environment.


Despite its resistance to moisture, silicone render is highly breathable. It allows water vapour to escape, preventing the buildup of condensation within walls. This is crucial in maintaining the structural integrity of internal walls and avoiding damp-related issues over time.

Versatile Aesthetics

Silicone render offers a wide range of finishes, from smooth and contemporary to textured and rustic. This versatility in aesthetics allows homeowners and designers to achieve the desired interior look and feel without compromising on the render’s functional benefits.

Low Maintenance

Once applied, silicone render requires minimal maintenance. Its inherent properties mean that it doesn’t easily harbour dirt or grime, keeping interiors looking fresh for longer. If it does need cleaning, a simple wipe-down usually suffices, making it a low-effort choice for both residential and commercial settings.

Long-lasting Finish

Silicone render is known for its longevity. Its resistance to common problems like cracking, fading, or peeling ensures that interiors remain pristine for years to come. This longevity not only keeps interiors looking great but can also lead to cost savings in the long run by reducing the need for frequent refurbishments.


The flexibility of silicone render makes it less prone to cracking due to minor building movements. This is particularly beneficial in regions or buildings where subtle shifts might occur, ensuring that the interior walls remain intact without unsightly cracks.

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