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Case Study – Spray Rendering

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.

Our next project is an intriguing collaboration with Roger from SkillBuilder. Roger was initially renovating a home using traditional silicone render application techniques. However, as he was working alone, the render dried too quickly. Thankfully, Paul Harris and Paul Christmas offered to lend a hand in recovering the project, with the help of a spray machine. Therefore, we get a chance to examine a spray rendering project in our case study series.

Project details

– Substrate: Brick and old render
– U-Value change: N/A
– Basecoat: EWI-225 Premium Basecoat
– Finish: EWI-075 Silicone Render / EWI-050 Mosaic Render
– Colour: Elderflower / Black
– Location: Reigate
– Installer: Roger @ SkillBuilder

The build-up – Spray Rendering

The initial premise of Roger’s project was the re-rendering of the facade as it was subject to significant fading and cracking. As aforementioned, the newly applied render, unfortunately, dried too quickly. This was mainly due to the excessive sun and the inability to maintain a wet edge. Projects such as this will require 2-3 skilled professionals to ensure the render dries properly.

The following solution relied on the expertise of our very own Messrs Harris and Christmas, who urged Roger to utilise a spray machine. A render spray machine allows one to apply render incredibly quickly and spread it evenly. The render is atomised before being ejected from the nozzle, therefore ensuring an even spread. As silicone render is a thin coat render system, Roger was able to apply it quickly and efficiently over the previously cracked render surface.

Whilst providing some training, Paul Harris also supplied Roger with several tips for using spray machines:

Tip 1 – Take a clear bin bag, poke a hole through the bottom, and then tape it to the inside of the hopper. By doing this, you won’t need to clean the inside of the hopper at the end of the day. You can use any sort of tape to attach it. Just ensure that the bag does not drop down into the mechanism below.

Tip 2 – Always spray into an empty bucket or back into the hopper initially as the initial burst of material is usually lumpy.

Tip 3 – When spraying, avoid unnecessary pauses that can allow the plaster in the nozzle to dry and possibly cause clogs.

Benefits of spray rendering

Render spray machines have transformed the construction and renovation industry by offering a range of efficiencies. One of the most prominent benefits is the sheer speed and efficiency of these machines. They are adept at covering vast areas, such as sides of commercial buildings, in a fraction of the time manual methods would take. This rapid coverage is not just about speed; the consistent flow and automated delivery also ensure that there’s a steady, uninterrupted application, which in turn helps maintain a consistent pace of work.


The uniformity of the application is another major advantage. Unlike manual methods that might lead to uneven patches or overly thick spots due to human error, machines distribute the render in thin, even layers, ensuring a smooth and well-bonded finish. This precision, paired with the machine’s ability to be calibrated to release the exact amount of render, results in significant waste reduction. Modern machines even have the capability to recycle excess render, further cutting down on material wastage.


Labour efficiency is another domain where these machines shine. The faster application rates mean fewer skilled labourers are required on-site, which leads to a quicker project turnaround. This efficiency doesn’t just have implications for time and cost; it also means enhanced safety. Ergonomically designed machines reduce the strain from repetitive motion or heavy lifting. Moreover, the ability to apply render from a distance reduces risks associated with being too close to a wall, such as falling debris.


They are designed to handle a plethora of materials, from traditional lime-based plasters to contemporary acrylic renders. This adaptability also extends to the machines’ functional aspects as well, with a variety of attachments available to achieve different textures and finishes.

Furthermore, the method of application ensures better adhesion. Machines apply render using optimal pressures, fostering a robust bond to the substrate. In some cases, the spraying process can even introduce air into the mix, improving the render’s workability and bond.

Logistics and training

A significant logistical advantage is the reduced need for extensive scaffolding. With some machines equipped with extended hoses or booms, the render can be applied from the ground to higher levels. Mobile units also offer the added benefit of easy relocation around a site, reducing setup and breakdown times.

Lastly, the standardisation of machine operation training ensures that operators not only achieve a consistent skill level but are also well-versed in safety protocols. This dual focus on skill and safety can also lead to higher-quality results and safer work environments.

In wrapping up, while the initial cost and upkeep of a render spray machine can be considerable, the multitude of benefits they offer, from labour and material savings to improved quality of work, make them an indispensable tool for substantial rendering projects.

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