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The product K-rend has become extremely popular in recent years. It gives a nice-looking finish to the exterior of the property and comes in a huge variety of colours and textures so the home can be made to look completely unique. It is also weather-proof and breathable, which protects the property from condensation. And it is quicker to apply than traditional sand and cement rendering. K-rend, however, is not without its problems. And these are definitely issues that should be thought about carefully before going down the K-rend route.
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With sand and cement rendering, you first apply a scratch coat. This is a layer of the render that is applied to the wall, smoothed, and then scratched with a rendering comb to make a rough surface for the next layer to adhere to. This next layer is the topcoat and it is a weaker mix that is smoothed out to create the right finish.
With K-rend, you only apply one layer that is sprayed on. In other words, K-rend is only the topcoat. And, without the scratch coat underneath, the topcoat can be so thin that you can see the stonework underneath. This obviously isn't the nicest of finishes and can make the rendering look sloppy.
K-rend is advertised as maintenance-free and that is true, at least when it comes to painting. Unlike sand and cement render, K-rend never needs to be painted because it is coloured all the way through. Unfortunately, however, it is prone to mould and algae growth (especially in coastal areas) which can make it look quite unsightly quite quickly. You can buy special pesticides to treat it with but actually cleaning the algae off once it's there can be quite a chore. The sheer number of K-rend cleaning companies that have popped up in recent years really is a testament to how much maintenance may need to be done to keep the K-rend finish looking clean.
One of the benefits of K-rend that many people talk about is that it can even be applied in the rain, unlike sand and cement render. What many people don't realise, however, is that K-rend has its own weather restrictions. It can only be applied when the temperature is above 5oC. This can be a problem, especially in the UK winter months! And, of course, the last thing anybody wants is to pause a job halfway through because the temperatures have dropped.
While K-rend on the surface is much easier to apply than traditional render, the barrier to entry into using K-rend is quite high. People who want to start using K-rend need to pass a certification course to be able to apply it. They will also need to buy specialist equipment, such as a sprayer and a specific type of mixer. These extra tools and training needed can filter through into the cost of labour.
With traditional render, if there is any damage or cracking it can be easily patched up. Things aren't quite so simple with K-rend, unfortunately, and this mainly due to the colouring. Because K-rend is coloured, and not painted over, if the colour of the patch is even slightly different to the rest of the wall, it stands out like a sore thumb. This isn't easily fixable unless you go ahead and paint the whole wall which, of course, defeats the object of K-rend not needing painting.
Cracking is a particular problem when there is some structural instability in the building. In these cases, wire mesh should be applied to hold that area of the wall in place. But because K-rend is quite thin, hairline cracks can quite easily appear if there is any movement in the wall at all. This can be true of other types of render as well but, as we have mentioned, K-rend can be very difficult to patch if there are any cracks.
Because of the silicone used in K-rend, it isn't as environmentally friendly as traditional mineral-based renders. Mineral render has a 10% lower global warming impact than silicone-based renders, and a 30% lower impact on the aquatic environment. Of course, in the grand scheme of things, the impact of rendering one property in a less environmentally friendly way isn't going to be that great. But the wholescale impact of using silicone-based render instead of mineral-based render could add up quite quickly.
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Traditional sand and cement rendering does have some disadvantages when compared to K-rend, which is why K-rend has become so popular. The main one being that it does need to be painted every 4-5 years. It is also more difficult to apply since it needs to go on in two coats and it can't just be sprayed on in the same way that K-rend can. With that being said, given the above problems with K-rend, there are some advantages to using traditional rend instead.
1) Because it is a painted surface, algae doesn't grow on it.
2) It provides more insulation.
3) It is easy to do patchwork if there are any problems.
4) It is cheaper.
5) It improves the durability of the walls.
6) It is easy to change the colour and look.
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K-rend does give a smooth and sophisticated look to a property if it is applied well. The biggest advantage of K-rend over traditional rendering is that it never needs to be painted. Because it only goes on in one layer, however, it can go on thin enough to show the stonework underneath. It is also prone to algae growth, which is a particular problem in coastal areas. It can only be applied when the temperature is warm enough and, if there are any problems, it is very difficult to patch without the patchwork being glaringly obvious. It also isn't as environmentally friendly as traditional rendering because of the silicone.