How to Achieve a Flawless Render Finish

Render is a popular solution to improving the external facade of your home. However, applying and achieving a flawless render finish can be slightly tricky if you're unsure of the ideal steps. There are several different options for render finishes depending on the result you're looking for. Silicone render is the premier thin coat solution for weatherproofing, while monocouche faithfully mimics stonework. Lime render, on the other hand, is a fantastic solution for heritage restoration with breathability in mind. Mineral render is the final option, particularly suitable for winter applications due to the quick drying times.

Flawless render finish with silicone render

Silicone render is renowned for its excellent hydrophobic properties, contributing to its durability and weather resistance. These properties stem from the fascinating science behind the lotus effect and the incorporation of silicone particles. The lotus effect is named after the plant, which exhibits remarkable water-repellent characteristics. The lotus plant leaves have a micro- and nano-structured surface that minimizes the contact area for water droplets. As a result, water beads up and rolls off the surface, taking dirt and debris with it. This self-cleaning property is what makes the lotus plant an inspiration for hydrophobic technologies. Silicone render incorporates silicone particles, which play a crucial role in mimicking the lotus effect. These particles are dispersed throughout the render mix, creating a surface that is highly resistant to water penetration. Silicone particles create a rough microstructure on the render surface. This microstructure reduces the contact area between water droplets and the surface, causing water to bead up rather than spread out. Silicone has a naturally low surface energy, so it does not attract water. This property enhances the water-beading effect, making it difficult for water to adhere to the surface. As water beads up and rolls off the silicone render surface, it carries away dirt and other contaminants. This self-cleaning mechanism helps to maintain the render's appearance and longevity. Here's how to achieve a flawless finish with silicone render:

Mixing render

Proper mixing is crucial to ensure the aggregate is evenly distributed. Use a mechanical mixer to blend the render until it has a consistent, smooth texture. Avoid over-mixing, which can introduce air bubbles.

Working in sections

Render must be applied in manageable sections to maintain consistency. Plan your work area and divide it into sections that you can complete in a single session.

Maintaining a wet edge

Always maintain a wet edge to prevent trowel lines and ensure a seamless finish. This means that you should overlap the newly applied render with the previously applied render while it is still wet.

Working ahead of the sun

Using a sponge float

After applying the render, use a sponge float to smooth the surface gently. This helps to bring the aggregate to the surface and creates a more uniform finish.

Using a plastic float

Finally, a plastic float distributes the aggregate evenly and achieves a smooth finish. This step is crucial for giving your render a polished, professional look.

Monocouche render finish

Monocouche render is a modern, single-layer rendering solution that has gained popularity for its ease of application, durability, and aesthetic versatility. The term "monocouche" is derived from the French words for "single layer" or "single coat," highlighting its defining feature. One of the major advantages of monocouche render is that it is available in a wide range of pre-mixed colours. This eliminates the need for painting, as the colour is integrated into the render itself, providing a long-lasting and uniform finish. Monocouche render is highly durable and weather-resistant. It is formulated to withstand various environmental conditions, including freeze-thaw cycles, UV exposure, and moisture. This durability helps maintain the building's aesthetic appearance and structural integrity over time.

Applying the render

Apply render to the primed surface in two passes. Apply the first pass with a stainless steel trowel or spray pump at a thickness of 10mm and embed fibreglass mesh in the first pass. Then, the second pass was applied to an 8-9mm thickness.

Scratching it back

Once the render has started to set, but is still soft, use a scratching tool to texture the surface. This achieves the desired texture and allows the render to cure evenly, reducing the risk of cracking. You'll need to scratch it back 2-3mm to achieve the correct depth of application and uniformity of finish.

Lime render - breathable render finish

Here’s how to achieve a flawless finish with lime render:

Mixing

Mixing lime render is a delicate process. Lime render typically consists of lime putty or hydrated lime mixed with sand. Mechanical mixing is recommended to achieve a consistent texture. Allow the mixed render to rest briefly to ensure proper hydration.

Applying

Apply the first coat of lime render with a trowel, pressing it firmly into the substrate. This base coat should be around 10-12mm thick. Allow it to cure slowly and keep it moist by misting it with water, especially in dry or windy conditions.

Building up layers

Lime render is typically applied in multiple layers. Once the base coat is partially set but still damp, apply the second coat, slightly thinner than the first. Smooth the surface with a trowel to ensure an even application.

Finishing

After the final coat has been applied and has started to set, use a wooden or plastic float to achieve the desired texture. Lime render can be finished with a smooth or textured surface, depending on your preference.

Curing

Mineral render - quick drying in wintertime

The final option is mineral render, which is applied by hand or by a spray machine. The process is very similar to that of other renders; however, it does not need to be floated or scratched back. Mineral render must be sealed with Silicone Paint to provide hydrophobic qualities. It is far more susceptible to lime bloom if it is not sealed. Mineral render is often chosen for winter application due to its quick drying times.