When it comes to maintaining and renovating older properties, one of the critical considerations is the type of render applied to their exterior walls. Many older homes prior to the 1920s were constructed using lime mortar and are only a single brick construction. The lime mortar is a material that allows the building to “breathe” and naturally manage moisture. This was great when heating was just the open fires and no hot water. However, we now heat our homes with central heating and our bathrooms are now internal creating more moisture than ever before and this additional moisture needs to escape through the walls.
In more modern times older homes have had sand and cement renders applied to their homes which can have a detrimental effect on your home. In this post, we’ll delve into how sand and cement render can contribute to dampness, mould and condensation in your home, and why its essential to opt for more sympathetic render options for long-term preservation.
The Issue with Sand and Cement Render
Sand and cement render, although commonly used for its affordability and robustness, can pose serious problems when applied to older properties. Unlike lime mortar, which is porous and allows moisture to evaporate naturally, sand and cement render tends to trap moisture within the walls. This can lead to a host of issues, including:
- Dampness: The impermeable nature of sand and cement render prevents moisture from escaping, causing dampness to build up within the walls. This dampness can then migrate inside, leading to unsightly damp patches on interior walls and a generally uncomfortable living environment.
- Mould Growth: Dampness provides the perfect environment for mould to thrive. Mould not only damages the aesthetics of a property but can also pose health risks to occupants, particularly those with respiratory conditions.
- Condensation: The inability of moisture to escape through the render can lead to condensation forming on the inner surfaces of the walls. This can result in a perpetually cold and damp atmosphere within the house.
The Interaction Between Sand and Cement Render and Lime Mortars
One crucial factor contributing to the issues mentioned above is the interaction between sand and cement render and the lime mortars used in older homes. Lime mortar is highly breathable and flexible, allowing for the movement of water vapor through its structure. However, sand and cement render is more rigid and less breathable, creating a barrier that prevents the walls from releasing moisture as effectively as lime mortar does.
Furthermore, over time, the chemical reactions between the sand and cement render and the underlying lime mortar can lead to deterioration. Sand and cement render is more rigid and less accommodating to the natural expansion and contraction of the building caused by temperature and humidity changes. This can result in cracking and detachment of the render, allowing even more moisture to infiltrate the walls.
The Need for Sympathetic Renders
To ensure the longevity and health of older properties, it’s imperative to opt for more sympathetic render options that are compatible with the original construction materials. Lime-based renders, for example, offer several benefits:
- Breathability: Lime-based renders are porous and allow moisture to evaporate, preventing the accumulation of dampness and mould growth.
- Flexibility: Lime renders are more flexible than sand and cement renders, accommodating the natural movements of the building without cracking or detachment.
- Compatibility: Lime-based renders are compatible with lime mortars and older building materials, reducing the risk of chemical reactions that can damage the structure.
Conclusion
The impact of sand and cement render on older properties cannot be understated. The use of this type of render can lead to dampness, mould, and condensation, compromising the structural integrity and comfort of the home. To address these issues and ensure the longevity of these historic properties, it’s crucial to choose render options that are sympathetic to the original construction materials, such as lime-based renders. By making informed choices and prioritizing the preservation of older homes, we can continue to enjoy their charm and character for generations to come.
