What causes render cracking?

Why does render crack?

 A Big Question! There are many reasons why render can crack. But if you can rule out causes that come from the build process and movement in the underlying structure or ground, then look to the products and application. With SAS Europe you have the support of our technical team to learn why render cracks, and get advice on the right product and application for a great result.

The right product for the right substrate

hydration crackingWe all know that materials can get changed during a build, so it’s imperative to check the substrate is what you were told. Using the wrong render product for the substrate can cause the water to dry out too fast, due to suction from the substrate, so causing cracking. Delamination occurs if the render product does not adhere – either by chemical key or by suction. Again, this is down to the choice of product for the substrate. The SAS technical team will advise you on choosing the right render products and how to achieve a great finish. See also our Guide To The Right Render System.

Drying time and temperature

Get to know the product you are using – not all renders have the same drying time and tolerances – just give us a call if you need advice. Drying too fast due to heat or wind can cause hydration cracking or a powdery surface. Drying at different times can cause differences in surface colour of the render, so leading to a poor looking finish. For cold-weather rendering, you can look at ProRend Mineraltex that can be applied in temperatures as low as 0 degrees, or our GoRend HBS monocouche can be used with the GoRend Speed Up accelerator to allow for same day scratch back.

Correct application and reinforcement

reinforcementUse the recommended reinforcement for your render product, as using an inferior mesh or applying it incorrectly can also cause cracks. Here is a sample we investigated where the mesh was not embedded in the basecoat and was the cause of the render cracking.

Assistance and training

To keep your team up to date with render application and compliance best practice, take a look at our one day training courses. On completion, you will be added to our Trained Applicator Network and have your details put forward for external render projects. Our technical team is available 830am -430pm Monday to Friday, we are here to help – call us directly from site for instant advice. We can help with the design of your project from day one.
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