With all exterior decorating projects it is crucial that you apply the correct paint, however one surface that this is particularly true with is lime render. But what is lime render, what paint should you use and what do you need to consider. Our team of experts have put together this guide with everything you need to know about painting lime render, so you have all the information you need to get started.
What Is Lime Render?
Lime render is a traditional form of exterior wall render that is distinctive thanks to it's high breathability and aesthetic appeal. In contrast to more modern, hard cement & sand render, lime render is soft, allowing it to naturally erode over time and providing it with a more even appearance.
While lime renders are applied to modern properties, they are generally used on properties pre-dating the 1800's. The reason they are best suited for these properties is their high breathability. Breathability refers to the ability for water vapour to freely travel through an exterior wall. If a render or coating is not breathable, it will trap moisture within the external wall of a property, which will build up over time and cause significant issues. These issues can vary from interior damp problems to significant structural damage to brickwork. While breathability is crucial on any building, it is particularly important on older properties as these are designed to breathe naturally in order to regulate moisture levels. They achieve this by allowing moisture to penetrate into the external wall and then evaporate away.
The other reason lime render is usually used on older properties is that are not built with the foundations that properties have nowadays. This means that renders on older properties must be flexible enough to move slightly with the building. If a hard, modern cement render is used, any movement will cause cracking on the render which can must be repaired.
Overall, the combination of breathability, flexibility and the beautiful long-term finish lime render can achieve, makes it a popular choice of render, which is making a comeback in recent years.
Painting Lime Render
Lime render is not suitable in combination with all exterior masonry paints. The breathable nature of lime render means that a breathable masonry paint must be used, otherwise the core benefit of lime render is lost and the damaging build up of moisture will begin. For this reason, lime render was traditionally painted using lime wash, which is a simple form of render paint that is made using a formulation of natural ingredients, commonly consisting of lime putty that has been watered down to create a thin decorative coating. Having been around for thousands of years, limewash has been a staple form of paint finish on older properties, and is sometimes used on newer properties today.
While limewash can be coloured and is breathable, it does not offer any protection to lime render, which allows moisture to absorb into the external walls of the property. This moisture, while lime render is designed to absorb this, accelerates the deterioration of the exterior wall, causing damage. Furthermore, due to the solid wall construction of many lime rendered properties, there is no cavity to prevent the moisture from soaking through to the interior wall of the property, which can cause damp conditions in areas particularly prone to water ingress. Lastly, the property due to having wet walls has a poorer thermal performance, as wet walls transfer heat much quicker than dry materials. This heat is directed to drying the external walls rather than heating the property, meaning properties that have high moisture conditions can be difficult to heat.
This is why silicone masonry paints were developed. While the majority of masonry paints are acrylic-based, meaning they are not breathable, silicone masonry paints remain completely breathable once applied. While remaining breathable, some of these silicone masonry paints create a water repellent surface on external brick, stone & render, meaning that any rainwater simply runs off the external wall before it can absorb into the substrate. This keeps external walls dry, improves thermal efficiency and protects the render from the damage that moisture can cause. Aside from the protection that silicone masonry paint can provide, it also prevents the time-costly process of regularly applying limewash. Limewash not only can take up to four coats to apply, but it will generally last anywhere up to 5 years. A good quality silicone masonry paint can be applied in two coats and will not have to be applied again for 20+ years, meaning once the lime render is painted, it will remain that way for decades to come without constant maintenance.
What Paint To Use On Lime Render
Emperor Masonry Paint contains the latest super-hydrophobic technology that lines the pores of external walls without sealing them completely. This prevents water from entering the surface, while allowing water vapour to freely pass through.
In independent tests conducted by UKAS accredited laboratory Lucideon, Emperor Masonry Paint was found to have a number of benefits. It was firstly demonstrated that the masonry paint prevents 96% of water absorption, meaning rainfall cannot soak into painted render, which is the key driver of external wall damage. While providing this level of weather protection, a wall painted using the masonry paint was shown to have an SD value 0.56, while a bare wall had an SD value of 0.57. While any coating with an SD below 1 is considered breathable, this test demonstrated that there was almost no change in the ability for water vapour to escape the surface once waterproofed.
This double action that keeps external walls dry results in Emperor Masonry Paint being heat retaining. In the test, there was found to be a 6°C difference between the wall coated in Emperor Masonry Paint and the bare wall, demonstrating the ability for the paint to retain heat due by keeping the wall dry.
Lastly, after the 25 year accelerated weathering test has completed, there was no sign of deterioration in appearance or performance of the exterior wall treated with Emperor Masonry Paint. It continued to repel water and showed no signs of peeling or blistering, which is a common problem with masonry paint. This is thanks to the masonry paints ability to prevent moisture build up, which once it gets behind the paint film causes it to peel off the surface.
Due to this, a lifetime guarantee is offered on the product, ensuring it's performance over decades. Following the results of this test, Emperor Masonry Paint was subsequently verified by the Energy Saving Trust for it's heat retaining properties, which aid the energy efficiency of a property. By preventing unnecessary heat loss, a saving can be made on energy costs, helping to save money and prevent energy waste.
- Water repellent
- Highly breathable
- Heat retaining
- Verified by the Energy Saving Trust
- Prevents discolouration
- Prevents penetrating damp
- UV resistant
- Independently tested and certified
- Comes with a lifetime guarantee
Why Paint Lime Render?
There are a number of common reasons why people choose to apply a paint to lime render:
Probably the most common reason why you may be thinking of painting lime render is for a change. Painting exterior walls is the most effective way to add kerb appeal, which can add value to the property. Masonry paint allows you to add personality to your external walls, whether you want to opt for a crisp brilliant white, or a unique pale pink that will make your home stand out from the crowd. Using masonry paint gives you the opportunity to update your lime render and introduce something new to the look of your home.
As we have mentioned, lime render is soft and susceptible to weathering. While it is designed to naturally erode, the time may come that you decide that protecting the render, and thus preventing any moisture ingress may be in your best interests, especially if you are suffering from damp. Typically, limewashes require maintenance every few years while standard acrylic masonry paints last between 5-15 years. The weather protection and durability of Emperor Masonry Paint means your lime render will be protected for 25+ years without the need to clean, recoat or repair it.
Painting any external wall is a cost-effective alternative to re-rendering a property. Rendering will easily cost well into the thousands, with the cost of labour and materials. Paint can be applied yourself at home or by a professional decorator for a fraction of the cost, plus it is much less invasive on your property than re-rendering, which can be a substantial home improvement.
Frequently Asked Questions
Q. How does silicone masonry paint self-clean?
One of the most common questions we receive regarding Emperor's super hydrophobic technology is how is it self-cleaning? It achieves this thanks to the water repellent surface it creates, that makes it very difficult for dirt and other debris to attach to the painted surface. If any dirt does attach to the surface, this simply falls off with any rainwater, meaning it does not need to be cleaned regularly like with a standard masonry paint. It also prevents any green growth or other fungus to grow on the render, keeping it looking clean and free from discolouration.
Q. What must you consider when painting lime render?
One of the most important aspects of any exterior painting is ensuring the surface is clean, sound and ready to be painted. Unlike harder forms of render, lime render cannot be power washed down when cleaning it as this can damage the surface. Instead, you must soft wash the lime render or clean it using a hose pipe. It is recommended once large-scale dirt is removed to apply a fungicidal cleaner which will kill any green growth or other fungus that is attached to the external wall. This prevents any fungus growing underneath the paint film that once it blooms, could cause it to lift from the render. By killing any growth, you can be sure that once the paint is applied, it will remain in tact for decades. Once completely dry, clean and sound, you can then apply your chosen paint for lime render, ensuring that there will be no rain during the application process as this will cause problems.
Want more information regarding painting lime render? Our in-house experts are on hand to answer any questions you may have about the full painting process. To contact one of our experts, simply email email@example.com, where they are always happy to give the latest help & advice regarding your property. Alternatively shop Emperor Masonry Paint today & get FREE next working day delivery on all orders.