When it comes to home renovations or repairs, one of the decisions homeowners often face is whether to apply lime plaster on an already plastered wall. Lime plaster has been used for centuries, known for its durability, breathability, and aesthetic appeal. However, it is crucial to understand the compatibility of lime plaster with existing plaster to ensure a successful and long-lasting finish. In this article, we will discuss whether lime plaster can be applied on an already plastered wall.
Understanding Lime Plaster:
Lime plaster, also known as lime stucco or lime render, is a mixture of lime, sand, and water. It has been used as a traditional building material for its numerous benefits. Lime plaster is flexible, allowing the building to expand and contract without cracking. It is also breathable, enabling moisture and vapor to escape, preventing the buildup of dampness and mold. Moreover, lime plaster offers an attractive finish with a smooth texture, making it a popular choice for historical and period buildings.
Determining the Compatibility:
Before applying lime plaster onto an already plastered wall, you must assess the compatibility between the existing plaster and lime plaster. Various factors must be considered in this evaluation:
1. Type of Existing Plaster:
- Traditional Lime Plaster: If the original plaster is lime-based, it is generally compatible with lime plaster. However, a thorough inspection is necessary to ensure no underlying damage or deterioration.
- Gypsum Plaster: Gypsum plaster is commonly used in modern construction. The compatibility of lime plaster with gypsum plaster depends on the specific circumstances. It is recommended to consult a professional plasterer or conduct a small-scale test before proceeding.
2. Condition of Existing Plaster:
- Sound and Intact: If the existing plaster is in good condition, free from cracks, lumps, or loose sections, it is more suitable for applying lime plaster.
- Damaged or Cracked: If the current plaster shows signs of damage, such as cracks or flaking, these issues must be addressed before applying lime plaster. Repairing any underlying damage is crucial to ensure a stable base for the lime plaster.
Preparing the Surface:
Preparing the existing plastered wall is vital to ensure the proper adhesion and longevity of the lime plaster. Follow these steps for surface preparation:
1. Cleaning:
- Remove any dirt, dust, or loose particles from the existing plaster using a stiff brush or vacuum cleaner.
- Thoroughly wash the wall with clean water and allow it to dry completely.
2. Repairing:
- Address any cracks, holes, or damaged areas in the existing plaster using suitable repair materials, such as lime putty or plaster bonding agents.
- Follow the manufacturer’s instructions and ensure the repairs are completely dry before proceeding.
Applying Lime Plaster:
Once the existing plastered wall is properly prepared, you can apply lime plaster using the following steps:
1. Mixing Lime Plaster:
- Mix the lime plaster according to the manufacturer’s instructions, achieving the desired consistency.
- Traditional lime plaster usually requires soaking the lime in water for several days before mixing with sand.
2. Applying the Base Coat:
- Apply a thin base coat of lime plaster onto the prepared wall using a steel trowel or plastering float.
- Ensure an even application, covering the entire surface.
3. Scratching and Dampening:
- Scratch the base coat with a rake or a comb-like tool to create a rough texture, increasing the adhesion of subsequent coats.
- Dampen the base coat with clean water, aiding the bond between layers.
4. Adding Additional Coats:
- Apply additional coats of lime plaster as necessary, allowing each layer to dry partially before applying the next.
- The number of coats depends on the desired thickness and finish. Typically, two or three coats are sufficient.
Lime plaster can be applied on an already plastered wall with careful consideration and proper preparation. Understanding the compatibility between the existing plaster and lime plaster is crucial, as well as ensuring the condition and stability of the existing plaster. By following the appropriate steps for surface preparation and applying lime plaster in multiple coats, homeowners can enjoy the benefits of this traditional and durable material, enhancing both the aesthetics and performance of their walls.