If you own or are looking at buying a property in the UK, especially from the mid-20th century, you’ve likely seen a distinctive, pebbly exterior finish on walls. This is roughcast. But what exactly is it, why was it so popular, and how do you maintain it?
At MidRender, we specialise in all types of render, and in this guide, we’ll give you a clear, simple breakdown of everything you need to know about roughcast.
In simple terms, roughcast is a traditional form of external plastering or rendering used on buildings. Unlike a smooth render, it has a coarse, lumpy texture because it contains a high proportion of aggregate (like small pebbles or gravel) which is thrown onto a wet base coat.
The classic roughcast mixture, often called "harling" in Scotland, typically consists of:
This process creates a hard-wearing, highly textured, and weather-resistant finish that has protected British homes for decades.
This is the most common question we get! While they look similar at a glance, the key difference is in the application process:
The result? Roughcast has a more blended, uneven texture, while pebbledash has a more defined, uniform pebbly surface where you can see individual stones clearly.
Why did roughcast become so popular across the UK? Here are its main advantages:
No building material is perfect. It's important to be aware of the potential issues with roughcast:
Maintenance Tip: Regularly inspect your roughcast for cracks. For cleaning, a softwash (low-pressure cleaning) is recommended, as high-pressure power washing can damage the surface and force water behind the render.
Roughcast remains a viable and durable option, particularly if you are renovating a period property and want to maintain its original character.
However, modern render systems (like silicone or acrylic renders) offer improved flexibility, breathability, and a wider range of colours and finishes. The best choice depends on your property's age, location, and your personal aesthetic preferences.
If your home's roughcast is looking tired, stained, or has visible cracks, it's time to get a professional opinion. At MidRender, we have the expertise to assess, repair, and restore roughcast finishes, or advise on the best modern alternatives for your project.
Contact us today for a free, no-obligation quote and let us help you protect and enhance your home.
Yes, you can paint roughcast, but it requires specific materials and techniques. Due to its highly textured surface, it consumes more paint than a smooth wall. It's crucial to use a breathable, masonry paint that can bridge the small cracks and adhere properly to the uneven surface. We recommend using a long-nap roller and often a sprayer for the best coverage.
A well-applied roughcast render is incredibly durable and can last 50 to 80 years or more with proper maintenance. Its longevity is one of the key reasons it was so widely used. The main threats are significant structural movement causing large cracks, or a poor original mix.
The application of roughcast can be more labour-intensive than a simple smooth render, which can increase the cost. However, when compared to pebbledash, the costs are often similar. Modern silicone renders may have a higher material cost but can offer savings in application time and long-term maintenance.
Roughcast saw a massive surge in popularity during the 1920s-1950s housing boom. It was a cost-effective, fast, and durable way to finish the new, often simpler brickwork used in suburban expansion. It perfectly suited the need for a low-maintenance, weather-resistant exterior that hid imperfections.
The staining is likely algae, moss, or dirt. The safest and most effective method is softwashing. This uses specialist biodegradable chemicals to kill the organic growth, which is then gently rinsed off. Avoid high-pressure power washing as it can damage the render, force water inside, and blast away the aggregate.
Roughcast itself is a weatherproof layer designed to prevent damp. However, if it cracks or fails, it can allow moisture to penetrate and become trapped against the wall. The real issue is often the lack of a cavity wall or inadequate ventilation in older properties, rather than the roughcast itself. Regular inspection for cracks is key to preventing damp issues.
