Rendered walls enhance durability, insulation, and aesthetic appeal, but Australia’s diverse weather conditions can significantly impact their performance and longevity. Using high quality products and render systems ensures your surfaces remain protected, but understanding how weather affects both the render itself and its application is key to achieving the best results.
We love Australian summers for beach days, but in our trade, they can throw setbacks. Heat, humidity, and unexpected rain can all impact how render cures, adheres, and performs over time. In this blog, we’ll explore how different weather conditions impact rendered walls and their application, plus practical tips for ensuring a flawless finish.
Heat and UV Exposure: How It Impacts Render and Application
Impact on Rendered Surfaces
Australia’s intense sun can be harsh on exterior surfaces. Prolonged exposure to heat and UV rays can:
Cause premature fading - Lighter colours reflect heat better, while darker colours absorb more, leading to faster colour degradation.
Increase the risk of cracking - Rapid temperature fluctuations cause expansion and contraction, which can lead to cracks, especially if expansion joints haven’t been correctly placed.
Accelerate surface degradation - Over time, excessive heat can weaken the binders in the render, reducing its protective properties.
Impact on Application
Rendering in hot weather comes with challenges:
Faster drying times - High temperatures can cause the render to dry too quickly, leading to poor adhesion and increased risk of cracking.
Inconsistent curing - If the render dries unevenly, it may develop weak spots that compromise durability.
Difficult troweling - Rapid moisture loss can make it harder to achieve a smooth, even finish.
How to Overcome Heat-Related Issues
Consider your colour choice - For surfaces with high sun exposure choose lighter colours to reduce heat absorption.
Use UV-resistant products - Tinted acrylic render systems offer excellent durability, flexibility and colour retention.
Apply a protective coating - Ensure your render system has a sealant finish which adds an extra layer of defence against UV exposure.
Ensure proper curing - Allowing each coat of render to cure correctly as per suppliers specifications before applying the next coat prevents premature cracking.
Rain and Moisture: The Risk of Water Damage
Impact on Rendered Surfaces
Water is one of the biggest threats to rendered walls, especially in areas prone to heavy rainfall. Poorly applied or low quality renders can absorb moisture, leading to:
Efflorescence - White salt deposits appearing on the surface due to water penetration.
Delamination - Water seeping behind the render can cause it to separate from the substrate.
Mould and mildew growth - Excess moisture can lead to fungal growth, affecting the render’s aesthetics and integrity.
Impact on Application
Rendering during or just before rain can cause major issues:
Render wash off - Rain can erode freshly applied render, ruining the finish.
Slow curing times - Excessive moisture can prevent proper drying, affecting adhesion.
Compromised strength - A weak bond may form if rainwater dilutes the render before it sets.
How to Overcome Rain-Related Issues
Use the correct system to suit the substrate - Different substrates require tailored solutions, which may include cementitious waterproofing, high water resistant renders, or primers to enhance adhesion and durability.
Apply a breathable, water repellent finish - Ensure the final coat is one that is water repellent to provide excelled moisture protection.
Ensure proper drainage - Gutters, downpipes, and sloped surfaces should be designed to prevent water pooling near rendered walls.
Avoid rendering when rain is forecast - Wait for clear weather to ensure proper drying.
Cover fresh render - Protective sheeting can prevent wash-off while allowing ventilation.
Humidity: A Hidden Threat to Render Longevity
Impact on Rendered Surfaces
High humidity levels, especially in tropical and coastal regions, can impact rendered walls in several ways:
Slower curing times - Excess moisture in the air can delay the drying process, affecting adhesion and durability.
Higher risk of mould and algae growth - Warm, humid conditions create an ideal environment for biological growth on rendered surfaces.
Weakened bond strength - Continuous exposure to high humidity can affect how well the render adheres to the substrate.
Impact on Application
Humidity can be tricky when applying render:
Slower setting times - High moisture levels can extend drying and curing time, leading to application delays.
Increased risk of efflorescence - Moisture trapped during curing can cause salt deposits.
Potential bubbling or blistering - If humidity prevents proper drying, surface defects may appear.
How to Overcome Humidity-Related Issues
Choose mould-resistant products - Acrylic Renders include anti-mould properties.
Use breathable coatings - A tinted acrylic render system allows moisture to escape while protecting against water ingress.
Allow for adequate ventilation - Encouraging airflow around your rendered surfaces reduces prolonged exposure to humidity.
Extend drying times - Allow extra time between coats in humid conditions to ensure proper curing.
Weather plays a crucial role in both the durability and application of rendered surfaces. Heat, rain, and humidity can all present challenges individually and together. By choosing high quality products and applying the right system for each substrate, you can ensure your render withstands Australia’s climate while maintaining a flawless, long lasting finish.
However, the key to a successful render surface isn’t just the products - it’s the expertise behind the application. Professional and experienced tradespeople, like our team at JM & MJ Solid Plastering, have applied render through countless Australian summers. We understand how to adjust techniques, mix ratios, and curing methods to suit varying weather conditions, ensuring a durable and high quality result every time.
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