Up until about 10 years ago, if you decided to render your property, the builder would most likely have used a sand and cement render. Sand and cement render is made by mixing 4 parts sand with 1 part cement and is applied to the substrate at a depth of about 10mm – 15mm. The problem with sand and cement render is that it has no give and no flexibility. Over the course of a year, your home will expand and contract as the weather changes, this of course only minute amounts, however in cold weather the walls of your house will actually shrink and the opposite is true during the summer months.
There’s a reason why building materials and the technology behind their production has changed. Sand and cement render is a very outdated, low-performance solution to creating a decorative finish on your property; these days, thin coat, through-coloured renders and breathable scratch renders are a more popular alternative for installers and homeowners alike. In this blog, we’re going to take a look at why sand and cement renders pale in comparison to thin coat render systems.
Sand and Cement Renders Crack
The problem with the older sand and cement renders is that as the building changes in size, the sand and cement render won’t move with it. The result is that the old sand and cement render will begin cracking. At first you will begin to see hairline cracks but as time goes on and water begins to get behind the render, it may begin coming off the walls.
One of the ways of limiting the cracking that occurs when sand and cement render is used is the addition of lime to render. When you mix lime in with sand and cement, the finished render coat will have greater flexibility because lime is so lightweight and breathable.The mixture will not be completely flexible so will still be liable to cracking, but it should be a significant improvement on sand and cement alone. The presence of lime in the render also improves its workability, making it easier to spread.
K-Rend also Cracks Eventually!
To be honest, any thick render system is liable to cracking; it is not just sand and cement render. K-rend and other scratch renders are also more likely to crack than more modern thin-coat renders. It’s not that they are bad products – in fact K-rend is probably the UK’s best selling render – but the unavoidable fact is that any render applied that thickly is more likely to crack.
Thin Coat Renders are Virtually Crack-Proof!
As time has gone on, people have been seeking ‘crack proof’ render finishes. Our thin coat render is just that. It has a flexible fibreglass mesh embedded within the basecoat adhesive and this gives it flexibility. The top coat render is also very flexible. If you put the render as a test on a piece of EPS, you can then flex the EPS and the render will still not crack.
When you consider the overall thickness of the EWI Pro render system then it is much much thinner than K-rend and other scratch coat renders. The basecoat adhesive is just 6mm thick, and the render topcoat can be as thin as 1mm, this takes the whole system up to a thickness of just 7mm. The flexibility of the components and the fact they are applied in such a thin layer means that the system will genuinely move with the building. This means that the render system will expand with the building during the warmer summer months, and when it gets cold in the winter the render system will shrink.
Which Thin Coat Render is Best for Crack Resistance?
At EWI Store we offer a comprehensive range of thin coat renders, all of which offer flexibility and crack resistance, and can be tinted to create any shade – catering to all tastes! However, each render offers unique benefits:
Silicone Render is our premium render. It offers excellent breathability and vapour permeability, so that moisture and water vapour can escape from the surface of the render – thereby helping to prevent damp and mould. Silicone Render is also hydrophobic and therefore any water is repelled from the surface of the render. Silicone Render is also unique in that it offers self-cleaning capabilities; this means that the render will actively prevent any build-up of organic growth, therefore maintaining a fresh facade for years to come.
Silicone Silicate Render is our most popular hybrid-silicone render. Silicone Silicate Render is our best value render, offering the key benefits of a thin coat render as well as the breathability and vapour permeability that the silicone provides. Silicone Silicate also provides an element of self-cleaning capabilities. This is a great render if performance and functionality at a great price point are key priorities.
Acrylic Render is our best value render, and is generally most thought of when it comes to coloured render. This is because Acrylic Render holds onto colour pigment really well, providing vibrant and long lasting coloured finishes that are resistant to UV. While Acrylic Render lacks the breathability of the silicones, it is our most impact resistant, so it’s excellent in terms of crack resistance.
Crack-Proof and Maintenance-Free Render!
The beauty of the thin coat render system is that once installed on your property it will genuinely last, with no cracking and no maintenance required. You can install the system on your property and then rest assured knowing the system will last decades!
We do recommend you get qualified installers to install the system though. The reason for this is that since the system is so thin, it is fairly tricky to install. Qualified installers will be able to get a lovely finish – one that you will be able to admire for years to come!
How Much Does Crack-Proof, Thin Coat Render Cost?
In terms of materials, at EWI Store we can provide everything you need for a thin coat render installation. However, often with this kind of work, it’s difficult to gauge how much it would cost. For a comprehensive idea of how much materials for a coloured render system could cost, check out our blog post ‘Coloured Render Cost per m2‘.
5 thoughts on “Sand and Cement Render vs. Thin Coat Render Systems”
We had sand and cement render applied two years ago and is now cracked everywhere FFS.
Hi Xander, if you had this done, check to see whether the company installing the sand and cement render offer any kind of warranty. If not (and you do have to pay for the work) then try and go for a flexible render system. Ideally one that has a fibreglass mesh embedded within it since this will dramatically reduce the risk of it cracking – the thin coat render systems we sell are in fact known in the industry as crack-free render systems!
We have been using thin coat render systems for the last 3 years and they work great. Customers like them cause they require little upkeep and really tidy up the external walls. Our guys also like them, cause Silicone render goes on so well. Defintely go thin coat render over sand and cement – you won’t be disappointed.
K rend does not crack if it is set up and applied properly ie fibrous mesh over lapped and tight into beads. K rend is a lime and silicone product, the lime is a natural material which is beathable just like the human skin it has pours allowing water to evaporate and to expand and contact with the help of silicone in the product to waterproof it. Build structure can be the cause of cracks, if the building is still settling or down to the foundation its built on, such as old mash lands and clay ect. In some cases with old weak building will need EML to reinforced it or to some extent knocking down and starting again. Expansion joints are another cause, where you see straight lined crack, all is needed is a double stop expansion bead to over come this.
Building in this day and age are thrown up with cheap poor material and are not left to dry and settle. There is way too much movement in these new builds. This is going to cause big problems in the near future.
Great breakdown of the differences between sand and cement render versus thin coat systems! I appreciate the insights on durability and application methods. It definitely helps in making a more informed choice for my upcoming project. Thanks for sharing!