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Why Does Modern Render Crack? - How Can You Prevent It?

Render has been used to protect the exterior of properties and improve their aesthetic appearance for generations. Over the years, render has been made from a variety of materials, all of which have been selected for their particular protective qualities. 

A lot of the time, render is used to cover up irregular surfaces or cheap building materials like breeze blocks. It is less commonly used to cover high-quality materials like brick and stone. Using render to cover less aesthetically-pleasing materials can help builders to achieve a great finish on a low budget. However, it can also create a number of issues if the materials or the render aren’t used properly.

If the render on your building is beginning to crack, identifying the underlying issue will help you to resolve the problem, protect your property and prevent the cracks from reappearing in the future. Keep reading to find out more.

The Problem with Cracks

While you may not think minor cracks on the façade of your rendered property are too serious, they’re often an indicator of an underlying issue. If this isn’t rectified, it could result in serious structural damage and ongoing issues. Fixing cracks, and finding the problems that caused them in the first place, will help you to keep your property in the best condition possible.

Structural Issues

Cracks that appear in exterior render can be caused by underlying structural issues. After all, if the building itself is subsiding, or if joints, corners and other potential weak spots aren’t 100% solid, the resulting movements will inevitably cause the render to crack. If you suspect this might be the cause of the cracks in your render, you’ll need to call a structural engineer in to take a closer look. Once the structural problem is correctly resolved, you shouldn’t have any more issues with the render.


The Render Dried Out Too Quickly

If the water evaporates from the render too quickly when it’s first applied, there may not be enough time for the render to properly bond. This can result in a blotchy and uneven appearance and cracks can occur. This issue is most common with dry-mix renders. To prevent it affecting your property, make sure render is applied in moderate temperatures. If you think the render is drying too quickly, simply splash it with water to slow it down.


Wind, rain and extremes of heat and cold can really take their toll on external render. Like all building materials, render has a lifespan, so if the render on your building is getting old, the cracks could be down to weathering. Sand and cement renders are particularly prone to weathering as they’re less elastic – and so less forgiving – than many modern renders. Luckily, a lot of render now comes with added polymers. These help to make the render more pliable and more waterproof, two things that can help to minimise the effects of weathering.

Rising Damp

Rising damp can have a serious impact on the structure of a building. It occurs when water travels from the bottom of a building upwards via capillary action. As it goes, it can cause walls to bulge, floorboards to warp and render to crack.

If this is the underlying issue at your property, you’ll probably notice other signs of damp alongside your cracked render. If you’re unsure if this is the problem, ask a surveyor to cast their professional eye over the building. There are a number of ways of treating rising damp. Your surveyor should be able to recommend the most appropriate option for your property.

Incorrect Application

Render that has been applied incorrectly is a lot more likely to crack. One of the most common mistakes is missing fibreglass mesh. When render is applied correctly, fibreglass mesh is embedded in the basecoat layer. The mesh is applied in overlapping strips. This reinforces the entire surface of the basecoat and increases its tensile strength. 

When this layer is done properly, it minimises any movements in the structure of the building. This goes a long way to eliminating cracks and ensuring a smooth, even finish.

In other cases, cracks may appear when the incorrect render has been chosen for the property. This is especially common when sand and cement render is applied to high-performance blockwork. These high-quality blocks are more elastic than sand and cement and so, when the blockwork shifts slightly, the render cracks.

This problem is difficult to rectify once the render has been applied. However, it can be avoided by checking which materials have been used for the substrate before the work begins. Choosing the right render for the substrate can make a big difference to its longevity and help to avoid future maintenance issues.

Maintaining Modern Render

In order to prevent cracks, discolouration and blotches appearing on the surface of a rendered building, the render needs to be properly maintained. This involves regularly treating the surface of the render to remove mould and algae and checking the render for faults and imperfections.

Spectrum has developed a patented render cleaning process that quickly and effectively removes stains, kills algae and returns render to its original aesthetic condition. Carried out using superheated steam and specially selected biocides, the process is incredibly efficient and can transform the look of a building finished with modern render.

Before we begin the cleaning process, our team carries out detailed building surveys. This gives us the opportunity to thoroughly inspect the property for existing cracks and faults. These are then reported to the property owner so they can be rectified before they cause more serious issues. The survey also allows us to properly identify the type of render that’s been used on the property. We can then select the correct cleaning process for the project.

Get in touch with our render repair team here.

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