28/08/2025
Traditional plastering is a centuries-old technique for finishing walls and ceilings by hand, using a material typically composed of lime, sand, and water, sometimes with fibers like horsehair for strength. This plaster is applied in multiple coats, usually a rough scratch coat, a leveling brown coat, and a smooth finish coat, to create a durable, breathable surface that can be applied directly to masonry or onto timber laths. This method is particularly suited for historic buildings due to the flexibility and breathability of lime plaster, which helps to manage moisture and prevent damage to porous building materials.
Key Characteristics
Materials:
Primarily lime, sand, and water, with optional organic fibers such as horsehair.
Application:
Applied by hand using tools like trowels and hawks.
Breathability:
Lime plaster is vapor-permeable, allowing buildings to "breathe" and moisture to escape, which is crucial for the longevity of traditional building fabrics.
Flexibility:
The inherent flexibility of lime plaster helps it accommodate movement in timber-framed structures without cracking.
Process (Three-Coat System)
1. Scratch Coat:
The thickest, first layer applied to the surface (like timber laths), which is intentionally left rough with grooves and scratches to create a strong base for the next coat.
2. Brown Coat:
Applied over the scratch coat, this layer is smoother but still textured, serving to level the wall and create a solid, uniform base for the final coat.
3. Finish Coat:
The final, thinnest, and smoothest layer, providing the desired surface finish.
Common Applications
Historic Restoration:
Ideal for older buildings that require materials to match their original character and function.
Timber-Framed Buildings:
The flexibility of lime plaster is essential for buildings with a lot of background movement, like drying green oak.
Direct to Masonry:
Can be applied directly onto masonry walls.