Lime plaster is often considered better than cement plaster in certain contexts due to several key advantages, particularly in terms of sustainability, breathability, and flexibility. Here are the main reasons why lime plaster might be preferred over cement plaster:
1. Breathability
Lime Plaster: Lime plaster is highly breathable, allowing moisture to pass through walls. This reduces the risk of dampness, mold growth, and moisture-related deterioration in buildings.
Cement Plaster: Cement plaster is less breathable, which can trap moisture inside walls, potentially leading to issues like dampness and mold, especially in older or poorly ventilated structures.
2. Flexibility and Durability
Lime Plaster: Lime plaster is more flexible than cement plaster, meaning it can accommodate slight movements in buildings without cracking. This flexibility also allows it to self-heal minor cracks over time.
Cement Plaster: Cement plaster is more rigid and prone to cracking when the building settles or shifts, leading to potential maintenance issues.
3. Environmental Impact
Lime Plaster: Lime production has a lower carbon footprint than cement production. Lime plaster can also absorb carbon dioxide from the atmosphere during its curing process, making it a more environmentally friendly option.
Cement Plaster: Cement production is energy-intensive and contributes significantly to global carbon dioxide emissions.
4. Compatibility with Historic Buildings
Lime Plaster: Lime plaster has been used for centuries and is often the best material for restoring or maintaining historic buildings. Its compatibility with older structures helps preserve their integrity and appearance.
Cement Plaster: Cement plaster can be too harsh for historic buildings, potentially causing damage to original materials and leading to a loss of historical authenticity.
5. Aesthetic Qualities
Lime Plaster: Lime plaster provides a softer, more natural finish that can be more aesthetically pleasing, especially in traditional or historic contexts. It also ages well, developing a patina over time.
Cement Plaster: Cement plaster has a harder, more uniform appearance, which might be less desirable in settings where a traditional or rustic look is preferred.
6. Health and Indoor Air Quality
Lime Plaster: Lime's alkaline properties naturally resist mold and mildew, contributing to a healthier indoor environment.
Cement Plaster: Cement plaster does not have the same natural mold-resistant properties, which might be a concern in damp environments.
7. Repair and Maintenance
Lime Plaster: Repairs to lime plaster are often easier and more seamless because new lime can bond well with the old, maintaining the building's integrity.
Cement Plaster: Repairs to cement plaster can be more challenging and may not blend as well with the original material, leading to visible patchwork.
In summary, while cement plaster is often chosen for its strength, fast setting time, and cost-effectiveness, lime plaster offers significant advantages in terms of breathability, flexibility, environmental impact, and suitability for historic and sustainable construction. The choice between the two materials depends on the specific needs and context of the project.