Drying and Curing Render
Drying and curing are two terms people regularly confuse regarding rendering. Although they are both part of the building and renovation industry and occur during the final rendering process, they differ in some ways.
Allowing the render to dry and cure properly makes a huge difference to the final look of the rendered surface.
Continue reading to learn more about drying and curing the render.
Drying
Most people will be more familiar with the term ‘drying’ as it is a common word and action that we practice daily.
In regards to render, the act of drying refers to the process of removing moisture from the render, resulting in a solid, dry render. As the water evaporates from the render, the render will shrink.
Curing
The curing process is a bit more complicated and is one that more people may be unfamiliar with.
Curing refers to the chemical reaction between the render and the air. It includes drying and ensuring the proper moisture levels and optimal temperature. Curing helps the render strengthen, and it can typically take days or weeks to complete, depending on various factors.
What Are the Benefits of Drying and Curing Render Properly?
Allowing the render to dry and cure properly results in a strong and durable render finish that not only looks great but also has functional properties.
The benefits include:
- Strength and durability: Increased strength and durability.
- Lower risk of damage or imperfections: Lessens the risk of cracks and imperfections forming over time as the render dries slowly and steadily.
- Aesthetic appeal: It looks better.
- Lower risk of mould and fungi growth: If the render is adequately cured, it prevents moisture buildup and reduces the risk of any mould or fungi growth.
- Bonds better: Better adhesion between the surface and render.
- Save money on energy costs: It provides better insulation, saving you money on your energy and heating/cooling costs.
Important Things to Remember
Here are some important things to remember when drying and curing render:
- Take your time: Take your time, and don’t rush the process.
- Follow the instructions: Follow the manufacturer’s instructions carefully so you’re doing everything correctly.
- Correct mixing ratios: Use the correct mixing ratios to ensure neat and even render layers. Nobody wants a clumpy and uneven-looking render.
- Render during the right weather: If you apply render to external walls, it is best to do it on a sunny or cloudy day (no rain) when the temperature is between 10 and 30 degrees Celsius. Rendering during a mild, dry day means the render can dry at a moderate pace—not too fast or too slow.
- Dry layers correctly: Wait for the first render layer to dry completely before moving on to another layer.
- Plenty of ventilation: If you’re rendering a wall internally, allow for plenty of ventilation. Proper ventilation allows the render to dry completely, reducing the risk of mould growth and cracks.
- Moisture: The rendered walls should be damp during curing to prevent them from drying out too quickly. Spray the walls with water daily during this process.
- Curing time: The curing process should start within 24 hours of the render application. On average, the curing process should take up to seven days. However, this depends on the type of render used, the climate, and the moisture levels.
Factors that Have An Impact on the Drying and Curing Process
Climate and Weather
If it is too cold, the curing process may be slowed down or stopped, weakening the render. In contrast, if it is too hot, the render dries quickly, leading to premature curing, resulting in cracked or damaged render.
Higher humidity levels can also slow down drying times, while lower humidity can help the render dry faster.
For the best drying and curing result, apply your render when the temperature is between 10-30 degrees Celsius.
Thickness of Render Layers
The thickness of the render layers also has an impact on the drying and curing time. The thicker the layer is, the longer it takes for the render to dry and cure, as more moisture needs to evaporate. In comparison, thinner layers take quicker to dry as there is less moisture.
The best practice is to apply multiple layers in thin coats and wait for each layer to dry and cure completely before applying the next one.
Render Mixture
If the render mixture contains a lot of water, it will take longer to dry, as the extra water must evaporate first.
The ratios of sand, cement, water, and additives all result in different render mixture consistencies, which impact the drying and curing time.
Surface Preparation
Different surface materials and how they are prepared all determine the drying and curing time of the render. Materials like brick, cement, or stone absorb moisture at different rates.
Preparing the surface by cleaning and priming it can reduce or extend the drying time of the render. Poorly prepared surfaces can result in the render and wall not bonding correctly, which extends the drying and curing time.
Ventilation
Proper ventilation and air circulation are essential for the proper drying of rendered surfaces. Ventilation is especially crucial for interior rendering jobs. An adequate airflow removes excess moisture and helps the render dry faster. When rendering interior walls, open as many windows and doors as possible.
Hydration Process
The total curing time for the render is determined by the hydration process and the resulting chemical reactions that occur during the render setting. Hydration occurs when the water reacts with the cement and transforms into a hard substance. The whole process can take anywhere from days to weeks.
During the chemical reaction, calcium silicate hydrate (C-S-H) gel forms, making the render strong and durable. Calcium hydroxide and calcium aluminate hydrate are also formed, impacting the setting and curing time.
Additives
Some render mixtures have added additives and modifying agents, which can impact the total curing time.
Accelerators, such as calcium chloride and sodium nitrate, speed up the curing process, while retarders, like phosphates and hydroxylated carboxylic acids, slow it down.
The impact of additives on render mixtures depends on the dosage and application method.
At Sydney Cement Rendering, we take pride in being Sydney’s trusted rendering experts and providing our customers with the highest quality rendering services. Contact us at 0402 704 984 or visit our website: https://sydneycementrendering.com/ to find out more about what we offer!