Applying a render coat to the exterior of a building is an excellent way of smartening up the property’s look relatively inexpensively.
In addition, using a render keeps moisture out of the house and protects the walls against weather-related damage.
There are several types of render to choose from, with silicone render being a popular choice for customers and contractors alike.
However, it does come with problems attached. This article assesses the issues of choosing a silicone render and other common questions around its use.
Silicone Render Disadvantages
Silicone rendering is a transparent, coloured, flat, water-resistant system which appears at first glance to be cost-effective and long-lasting. However, they can come with significant issues.
Typical disadvantages of silicone render include:
- Labour intensive
- Needs warm weather
- Not environmentally friendly
- Difficult to patch
- No changing of colour
These are described in more depth below.
Applying silicone render involves several stages, making it labour intensive and far from the quickest option when choosing render.
After the wall has been prepared, a basecoat needs to be applied to create a stable and level surface upon which the render can lie. That requires up to 48-hours to dry before applying a layer of primer ready for the silicone topcoat.
The topcoat is then applied using a plastic float to create a smooth and thin finish.
The thickness of the silicone top-coat should match the grain size of the render and should be applied in one go on each section of the wall to ensure you aren’t left with patches or lines where the render has been joined together in separate stages.
Depending on weather conditions, the whole process can take up to four days, proving costly when managing a renovation budget.
Needs Warm Weather
While silicone render can be applied in wet weather, unlike other finishes such as sand and cement, that benefit comes with a sting in the tail.
Silicone render cannot be applied in cold temperatures. Once the mercury drops below approximately 5⁰C, the render will not set because the water in the solution cannot evaporate. This can lead to it remaining wet on the wall and liable to frost damage. This can lead to cracks appearing in the render.
In addition, if the cold temperatures are accompanied by heavy rain, the silicone may wash off, leaving a poor finish.
This makes rendering with silicone between October and March in the UK a risky business with temperatures at risk of being lower than optimal.
Silicone is Expensive
While cheaper than external wall insulation, Silicone render is significantly more expensive than other rendering solutions such as sand and cement or monocouche render.
Costs will vary depending on property location and contractor. Most estimates show that silicone render is approximately 10-15% more expensive than monocouche render and can cost more than double a sand and cement mix price.
The additional cost is because silicone render is more flexible than other finishes since they will move with the building and, when appropriately applied, should not crack.
It is essential to consider whether the significantly more expensive silicone finish will be a suitable long-term investment when considering the right render.
Not Environmentally Friendly
The silicone used in rendering materials has a significant environmental impact compared to the ingredients in mineral-based renders.
Mineral-based renders have a 10% lower impact on global warming than one containing silicone and a 30% lower impact on water-based environments.
With many contractors increasingly turning to sustainable construction methods that don’t have a significantly adverse impact on the environment, creating the silicone additive produces hydrogen-chloride, which is a hazardous substance.
In addition, the silicone additive itself has low-toxic properties, which, while having a minuscule environmental impact when used on a single property, can add up when used en-masse.
Difficult to Patch
With other renders, such as sand and cement, any damage, such as cracks, can be easily patched up without affecting the overall look and finish of the property.
Silicone render, although durable, can be easily damaged when being cleaned with the wrong equipment, such as high-pressure jet-washers, or where cracking has occurred.
The colour in silicone render is applied with the render, rather than painted on top of the render as with many others. Where damage has occurred, it’s tough getting the colour of the repair to match the rest of the colour of the wall.
If the colour of the patch job is even slightly different to that of the original job, it will be noticeable. This isn’t an easy fix without re-rendering the entire wall, which can quickly become very costly.
No Changing the Colour
With a silicone render, the colour is applied as part of the finish, meaning that there is no need to paint over it as you would with mineral renders.
While this appears to be an advantage on the face of it, there is a significant downside if, once the render has been applied, a decision is made to change the colour.
While it would be a relatively simple task to overlay a different shade of paint on a sand and concrete render, it is impossible to paint on top of the silicone.
The only way to change the colour once a silicone render has been applied would be to remove the existing finish and start a time-consuming, labour-intensive and costly process again.
How Long Does Silicone Render Last?
Silicone renders are generally durable and can last longer than other more traditional mixtures, especially when combined with an adhesive base coat. In these cases, silicone rendering can last between 15 and 30 years.
However, some factors affect the durability and longevity of any render.
The property’s location plays a big part in how long the render can last before needing replacement. Properties in more exposed areas, such as the coast or high ground, are more susceptible to harsh weather conditions.
This is particularly true of properties in coastal areas where the local climate is likely to involve harsh storms whipping in off the sea and exposing house exteriors to wind and rain and saltwater damage.
In addition, any render is only as good as the contractor that applied it. As with any building work, the quality of workmanship varies from contractor to contractor. A render that has been poorly applied is likely to need replacing sooner than high-quality work.
Similarly, for a silicone render to last for as long as possible, it needs to be correctly cleaned and maintained to avoid the risk of cracking and other damage.
Benefits of Silicone Render
Of course, there are benefits to choosing to render with silicone.
Silicone render is one of the more durable surfaces available on the market and one of the most flexible. It can move in league with buildings, making it less likely to crack or become damaged as structures shift and settle.
Once the smooth finish of a silicone render has been applied, it is relatively straightforward to maintain and keep clean. There is no need to repaint every two or three years; instead, a warm-temperature, low-pressure jet washer should be enough to keep the fascia of the building looking fresh and like new for many years.
Indeed, another advantage of a silicone render is that the colour is part of the render itself, so by keeping the render clean, the colour remains sharp.
In addition, when applied well, silicone render’s durability means that the long-lasting nature could be an excellent long-term investment compared with other finishes.
For example, with most silicone renders lasting at least 15 years and often much longer, the additional extra cost could be worthwhile against the need to replace other types of renders every seven to 10 years.
Alternative Rendering Choices
If you’re unsure that silicone render is the right choice for your property or development, several other options are available, each with its own benefits.
Sand & Cement
A sand and cement render is very effective as an economical option, hides poor brickwork and can be easily repaired.
However, it needs to be regularly re-painted, can crack easily and isn’t as weather-resistant as more modern finishes.
Often known as a dry dash or wet dash render, pebble dashing is another good economical option that is easy to repair and offers an attractive look.
However, like sand & cement, it needs regular maintenance, is prone to cracking and isn’t as weather-resistant as other finishes.
A one-coat coloured cement finish that is very water-resistant, low maintenance and breathable, which helps with insulation.
It’s available in several colours that provide a crisp finish. However, as with other stone-based renders, it is liable to crack as the building moves.
A plastic added to the render during manufacture, acrylic render is very flexible and crack resistant, water-resistant and cheaper than silicone render.
However, as with silicone, it is not kind to the environment and isn’t as breathable as other more modern finishes.
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To Sum Up
Silicone render is very much in vogue when it comes to building finishes, and while on the face of it, there are plenty of benefits to choosing it, there are an equal number of problems that can arise from its use.
Understanding these problems and considering alternatives could save you from making a costly mistake.