Lime plaster has been used for centuries as a natural, breathable, and aesthetically pleasing wall finish. Unlike modern cement-based plasters, lime plaster is more flexible, environmentally friendly, and contributes to healthier indoor air quality. If you’re considering using authentic lime plaster for a DIY project, this guide will help you achieve a durable and beautiful finish.
Understanding Lime Plaster
Lime plaster is made by mixing slaked lime (calcium hydroxide), sand, and water. It differs from cement-based plaster because it hardens through carbonation, absorbing carbon dioxide from the air. This unique process allows it to remain breathable, reducing 漆喰DIY moisture-related problems such as mold and mildew.
Essential Tools and Materials
Before you start your DIY lime plastering project, gather the following tools and materials:
- Slaked lime or hydrated lime (Type S lime is commonly used for plastering)
- Sharp sand (Well-graded and clean, preferably washed river sand)
- Water
- Fibers (such as horsehair or natural fibers for added strength, optional)
- Trowels (stainless steel and wooden float for different finishes)
- Hawk (to hold plaster while applying)
- Mixing bucket or tub
- Drill with paddle mixer or hand mixing tools
- Protective gear (gloves, dust mask, and safety goggles)
Preparing the Surface
Proper surface preparation ensures good adhesion and longevity of lime plaster. Follow these steps:
- Clean the surface – Remove dirt, loose paint, or old plaster. If working on drywall, apply a bonding primer.
- Dampen the wall – Lime plaster adheres best to slightly damp surfaces. Mist the wall with water before application.
- Apply a key coat (scratch coat) – This rough base layer helps the next coats bond properly.
Mixing Lime Plaster
- In a large bucket or mixing tub, combine one part slaked lime with three parts sand.
- Slowly add water while mixing to achieve a smooth, creamy consistency.
- Allow the mixture to mature for at least 24 hours before application, ensuring proper slaking.
- Remix the plaster before use, adjusting the water content if necessary.
Applying Lime Plaster
- First Coat (Scratch Coat): Apply the plaster using a trowel, spreading it evenly to a thickness of about 5-7mm. Use a notched trowel or comb to create a textured surface for better adhesion.
- Second Coat (Brown Coat): Once the first coat has partially set but remains slightly damp, apply another layer of about 5-7mm. Smooth it out with a wooden float.
- Final Coat (Finish Coat): For a polished look, apply a thin final coat (around 3mm thick). Use a steel trowel for a smooth finish or a sponge float for a textured effect.
Curing and Maintenance
- Mist the plastered wall with water daily for at least 7 days to ensure slow curing and prevent cracking.
- Allow the lime plaster to fully carbonate, which can take several weeks.
- If desired, apply a natural sealant like lime wash or casein paint for additional protection.
DIY lime plastering requires patience and practice, but the results are worth the effort. It provides a timeless, breathable, and eco-friendly wall finish that enhances any space. By following these tips, you can achieve an authentic and durable lime plaster surface for your home.