We speak to hundreds of customers who are looking at re-rendering with a thin coat coloured render, and need a solution for their existing render. Often this is because the existing render is cracked and damaged with staining from plant life and general signs of weathering. Re-rendering the property with a coloured render can work wonders on giving it a facelift and improving the general aesthetics.
In a previous blog post, we discussed how to replace pebbledash with coloured render, however in this blog we’ll be taking a look at how you might want to go about replacing an existing sand and cement render with coloured render.
Re-rendering Sand and Cement Render with Coloured Render
As is often discussed here at EWI Store, sand and cement render is extremely prone to cracking and water ingress. In general, sand and cement render is just not a suitable material for the vast majority of buildings, especially older buildings and timber frame structures; and yet it is still so commonly used. With coloured render, you are guaranteed a flexible and strong render finish because unlike sand and cement render, coloured render is applied in an extremely thin layer which means it’s much less unforgiving.
Coloured render also gives you the option of choosing a breathable render, such as Silicone or Silicone Silicate, which prevents water ingress and water vapour build-up by allowing it to escape from the building through the external walls, where it can then evaporate off the surface of the render.
When considering re-rendering with coloured render, the most ideal place to start is by removing your cement render. This can be a pretty difficult process, as cement render is such a tough material and removing it poses a risk to the underlying substrate. Nevertheless, this is most likely the best course of action to protect your property against structural damage because Cement Render is incredibly liable to water ingress.
Re-rendering: Do I Remove or Repair my Sand and Cement Render?
If you’re considering re-rendering with coloured render, then most likely this is because your existing render has cracks within the surface. Unfortunately, as soon as the cracks start to appear then water ingress will undoubtedly follow. If this is clearly the case and your render is beyond repair then it will need removing. Once you’ve removed the render, you may need to repair the underlying substrate before you can go ahead with the re-rendering job.
On the other hand, if the render is in good condition it may be best to simply go over the top of the existing render with a coloured render system. Your installer will need to assess for any hollow patches and areas where the damage is too excessive to safely re-render. If the existing render is damaged or cracked in any way, then sometime down the line your new render may start showing cracks or it may even start falling off the wall, so ensuring the substrate is stable is essential.
How to Repair Sand and Cement Render
Often, sand and cement render was applied to buildings as a means of covering up cheap brickwork and to give an expensive-looking finish. When cracks start to appear in your render, it’s important to repair them as soon as possible in order to prevent water ingress. As soon as water gets behind the render, the process of freezing and thawing will eventually escalate the problem – leading to timber decay, internal damp and render falling off the walls.
If removing your existing render just isn’t possible without causing excessive damage to the underlying substrate, you may be able to patch repair it before applying a coloured render on top. You can use the Levelling Mortar to patch repair your existing render, as this can be applied at a thickness of up to 50mm, creating a smooth and stable surface for your new coloured render.
If your render has come away from the wall in some places completely, you can fill this using the Levelling Mortar, but we do recommend that you are careful to ensure that the rest of the render is stable enough to support a new coloured render.
Applying coloured render on top of existing render
Once you’ve established that your existing render is safe enough to re-render with coloured render, you first need to prime the substrate with the Water Based Primer. This will limit the absorptive capacity of the underlying sand and cement render and prevent it from drawing water out of the basecoat and creating a waterlogged mess underneath.
After this, you can use the Premium Adhesive as a basecoat, with Fibreglass Mesh embedded within it; each strip of mesh should overlap by 10-15cm. The reason we recommend using the Premium Adhesive is because it is much stronger than any of our other basecoat adhesives and will ensure a stable adhesion to the underlying render. Leave the basecoat to set for 24-48 hours, then you are ready to apply your coloured render.
We recommend using a Silicone Render because it’s extremely hydrophobic and vapour permeable. This means that it will prevent water ingress while at the same time allowing trapped water vapour to escape from its surface. It’s an ideal choice for old and new buildings as it’s extremely flexible so will not crack due to structural fluctuations.
And there you have it! How to re-render with coloured render. If you have any further questions or need advice about whether your property is suitable for re-rendering with coloured render, you can call our technical team who have all the technical know-how.
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