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Which Render is More Crackproof?

Last modified: 18.12.2023

When it comes to exterior finishes for buildings, the choice of render can make a significant difference not only in aesthetics but also in durability and maintenance. One of the key considerations is the render's resistance to cracking. Cracks in render not only diminish the visual appeal of a building but can also lead to more serious structural issues, such as water ingress and insulation problems. So, which render is more crackproof?

Sand and cement render is a time-tested blend of sand, cement, and, in some cases, lime. This mixture is known for its hard-wearing and robust qualities, making it a popular choice for a variety of construction projects. However, the rigidity that gives cement render its strength is also its weakness, as it's prone to cracking over time. These cracks can occur due to building movement, thermal expansion, and contraction, or even due to the render drying too quickly during application. Despite its susceptibility to cracking, cement render remains favoured for its affordability and ease of sourcing its components. It can be applied on a range of surfaces and is often chosen for its classic, textured finish. However, it requires regular maintenance and might need repainting or patching over time to maintain its appearance and integrity, especially in climates with significant temperature variations. Acrylic render stands out in the world of building finishes for its enhanced flexibility and aesthetic versatility. This type of render incorporates acrylic resins. This lends it a plasticity that significantly reduces the risk of cracking, a common issue with more traditional renders like cement. This flexibility makes acrylic render particularly suitable for buildings that experience slight movements or shifts. It can adapt without fracturing. Additionally, it boasts a vast array of colour options and can achieve smoother finishes compared to its cement-based counterparts. The inclusion of acrylic resins not only improves its resilience to cracking but also contributes to better water resistance and longevity. Acrylic render dries faster than traditional renders, making it a time-efficient choice for projects. However, it is typically more expensive than cement render. On the other hand, its durability and reduced maintenance needs can make it a cost-effective option in the long run.
Lime render, revered for its historical use and natural properties, offers a unique blend of breathability and flexibility. This makes it an ideal choice for older, heritage buildings. Its key component, lime, allows the render to absorb and evaporate moisture. Therefore, the risk of trapped moisture is reduced. Trapped moisture is a common problem in older buildings. This quality makes lime render particularly suitable for buildings constructed with materials that need to 'breathe', such as stone and brick. Unlike more rigid materials like cement, lime render is more flexible. As such it helps minimise the occurrence of cracks as the building naturally expands and contracts. The aesthetic appeal of lime render is another noteworthy aspect. It provides a traditional, textured look that ages gracefully, enhancing the character of historic buildings. However, it's slower to set compared to modern renders. It also requires skilled application and regular maintenance to preserve its integrity. Overall, this makes lime render a more labour-intensive and often more expensive option. Monocouche render, a through-coloured rendering solution, is gaining popularity for its ease of application and aesthetic appeal. The term "monocouche" originates from French, meaning "single layer". This modern render type is a blend of cement, lime, and special additives that enhance its durability and weather resistance. One of the standout features of monocouche render is its variety of colours, which are integrated into the material itself, ensuring a consistent and fade-resistant finish that doesn't require painting. Its texture can be tailored during the application, offering a range of finishes from scraped to roughcast. Monocouche render is also known for its breathability and water-repellent properties, making it suitable for a wide range of climates and building types. While it’s generally more costly upfront compared to traditional renders, its longevity and low maintenance requirements offer long-term cost efficiency, along with an attractive, modern facade. Silicone render represents the pinnacle of modern rendering technology, acclaimed for its exceptional properties that address many of the shortcomings of traditional renders. The incorporation of silicone resins in its composition imparts remarkable flexibility, which significantly reduces the likelihood of cracking, a common issue with more rigid render types. This elasticity allows it to adapt to the subtle movements of a building, providing a durable and long-lasting finish. Moreover, silicone render is highly water-resistant yet breathable, a dual quality that prevents water ingress while allowing moisture from inside the building to escape, thereby reducing the risk of dampness and mould. Its self-cleaning properties, where dirt and rainwater are effectively repelled, make it low maintenance and ensure the building retains its aesthetic appeal over time. Silicone render allows water to form droplets. This effect is often referred to as the 'lotus' effect. Available in a wide spectrum of colours, silicone render provides a smooth, contemporary finish that is resistant to fading. While it may be more expensive initially, its durability and minimal upkeep requirements offer cost-effectiveness in the long run.

Silicone render is renowned for its crack resistance due to several key properties inherent in its composition and structure:

  1. High Flexibility: Silicone render contains silicone resins, which impart a high degree of flexibility. This elasticity is crucial for crack resistance. It allows the render to expand and contract with the building's movements and thermal fluctuations without cracking.
  2. Breathability: Despite its water-resistant properties, silicone render is highly breathable. It allows moisture from inside the building to escape while preventing water ingress. This moisture regulation reduces the risk of cracks that can occur due to moisture expansion within the render.
  3. Strong Adhesion: Silicone render adheres well to various substrates, reducing the likelihood of cracks forming due to poor adhesion. This strong bond with the underlying material ensures that the render remains intact even with structural movements or environmental changes.
  4. Resistance to Environmental Factors: Silicone render is resistant to UV radiation and extreme temperatures, which means it doesn't degrade or become brittle over time. This durability helps maintain its integrity and elasticity, further preventing cracking.
  5. Micro-Cracks Self-Healing: Some silicone renders can 'self-heal' minor micro-cracks. The flexibility of the material allows it to close small cracks that may form, preventing them from becoming larger, more problematic cracks.
  6. Water Repellency: The hydrophobic nature of silicone render means it repels water effectively. This characteristic minimises the risk of water-related damage, such as freeze-thaw cycles, which can lead to cracking in less resistant materials.