1. Purpose
The purpose of this method statement is to ensure that cement and sand plastering work is executed systematically, ensuring quality, durability, and safety while adhering to project specifications and industry standards.
2. Scope of Work
This method statement covers the application of cement and sand plaster on masonry walls and ceilings, both internally and externally, on concrete, brick, or block surfaces.
3. Materials
- Cement: Portland cement as per ASTM C150 or equivalent.
- Sand: Clean, well-graded, and free from impurities; conforming to ASTM C144 or equivalent.
- Water: Clean and potable, free from any contaminants.
- Bonding Agent (optional): As per manufacturer’s recommendations (if required).
- Plaster Mesh: Galvanized expanded metal mesh or fiber mesh for reinforcement in areas prone to cracking (optional but recommended for large surfaces).
4. Tools & Equipment
- Trowels (steel and wooden floats)
- Hawk
- Plumb bob
- Spirit level
- Straight edge
- Buckets for mixing
- Mechanical mixer
- Measuring tape
- Brushes and sponges
- Scaffolding and ladders (if required)
5. Safety Precautions
- Ensure personal protective equipment (PPE) is worn at all times: safety helmets, gloves, goggles, and safety shoes.
- Proper scaffolding and ladders should be used for working at heights.
- Ensure proper ventilation during indoor plastering to avoid inhaling dust.
- Ensure safe handling of cement, as it is corrosive and can cause skin irritation.
6. Preparation
- Surface Preparation:
- Inspect the surface to ensure it is clean, free from dust, loose particles, grease, and oils. Any defects such as cracks or uneven surfaces should be repaired before plastering.
- Wet the surface adequately by spraying water, especially in hot climates, to prevent the rapid drying of the plaster mix. The surface should be damp but not soaked.
- For smooth concrete surfaces, apply a bonding agent if specified in the project documentation to enhance adhesion.
- Attach plaster mesh to areas of concern where cracking is likely to occur, such as joints between different materials or over large areas.
- Setting out Levels:
- Mark reference lines and levels using a plumb bob and spirit level for accuracy.
- Install guide screeds (temporary or permanent) as necessary to ensure the correct thickness of the plaster.
7. Mixing
- Proportion:
- The typical mix ratio for cement and sand plaster is 1:4 or 1:6 (cement: sand) by volume, depending on project specifications. The mix ratio may vary based on the application (e.g., external vs. internal walls).
- Mixing:
- Measure the required quantities of cement and sand based on the chosen mix ratio.
- Add water gradually while mixing using a mechanical mixer or manually until the mix attains a workable consistency.
- Ensure the mix is free of lumps and homogeneous. Avoid excessive water, which can weaken the plaster.
8. Application Procedure
- First Coat (Scratch Coat):
- Apply the first coat of plaster, typically 10 to 12 mm thick, onto the prepared surface using a trowel.
- Use the straight edge to level the surface by moving it in upward strokes to ensure uniform thickness.
- Once leveled, create a rough texture on the first coat by scratching it with a comb-like tool. This will provide a good mechanical key for the next coat.
- Allow the scratch coat to cure for at least 24 hours by keeping it moist with water.
- Second Coat (Finish Coat):
- After curing the scratch coat, apply the second coat, usually 6 to 8 mm thick, ensuring that it covers the rough surface of the scratch coat evenly.
- Use a straight edge and spirit level to ensure the plaster is even and straight.
- Smoothen the surface using a wooden float or steel trowel in circular or straight motions.
- In external applications or exposed surfaces, add a waterproofing admixture to the final coat if specified.
9. Finishing
- Final Smoothing:
- If a smooth finish is required, use a steel trowel to further smooth the surface once the plaster starts to stiffen.
- A sponge float can also be used to achieve a finer texture. Lightly wet the surface and use the sponge in circular motions to create an even texture.
- Curing:
- Begin curing the plastered surface after 24 hours of application.
- Cure by spraying water regularly for 7 days to ensure the plaster hardens properly and does not crack due to rapid drying.
10. Quality Control
- Surface Inspection: Check for uniform thickness, levelness, and plumbness using a straight edge and spirit level.
- Adhesion: Ensure the plaster adheres firmly to the surface without hollow spots by tapping the surface lightly.
- Finish Quality: Ensure a consistent finish without trowel marks, cracks, or patches.
- Curing: Verify that the surface is adequately cured to prevent shrinkage cracks.
11. Clean-Up
- Remove all excess plaster from tools and surfaces before it hardens.
- Clean the work area, including scaffolding, tools, and surroundings.
- Dispose of waste materials in compliance with environmental and site regulations.
12. Completion & Handover
- Conduct a final inspection of the plastered surfaces to ensure compliance with project specifications.
- Prepare the surface for any further treatments (e.g., painting, tiling) after the plaster has fully cured.
- Handover to the next stage of work with documentation indicating that plastering has been completed to the required standard.
Conclusion
Following this method statement ensures that cement and sand plastering is carried out systematically and safely, meeting both quality and safety standards. Proper preparation, material selection, and careful execution of each step are essential for durable and aesthetically pleasing plaster work.
