Method Statement for Cement and Sand Plastering on Masonry Surfaces
1. Purpose
The purpose of this method statement is to outline the process and procedures for applying cement and sand plaster on masonry surfaces to ensure quality, durability, and adherence to project specifications and safety standards.
2. Scope of Work
This method statement covers the application of cement and sand plaster on masonry surfaces, including brickwork and blockwork, for both internal and external walls.
3. Materials
- Cement: Ordinary Portland Cement (OPC) or as specified, conforming to relevant standards (e.g., ASTM C150).
- Sand: Well-graded, clean, and free from silt, clay, and other impurities; conforming to ASTM C144 or equivalent.
- Water: Clean and potable, free from harmful substances.
- Bonding Agent: As specified for enhanced adhesion on smooth surfaces (optional).
- Plaster Mesh: Galvanized expanded metal or fiberglass mesh for reinforcement over joints or cracks (optional but recommended).
4. Tools & Equipment
- Trowels (steel and wooden floats)
- Hawk
- Spirit level
- Plumb bob
- Straight edge
- Buckets for mixing
- Mechanical mixer
- Measuring tape
- Brushes
- Scaffolding or ladders (if required)
5. Safety Precautions
- Ensure all workers wear appropriate personal protective equipment (PPE) such as safety helmets, gloves, goggles, and safety boots.
- Ensure safe scaffolding and secure ladders when working at heights.
- Ensure proper ventilation when working indoors to avoid inhalation of dust.
- Handle cement with care to prevent skin irritation.
6. Preparation
- Surface Preparation:
- Inspect the masonry surface to ensure it is structurally sound, clean, and free of loose materials, dust, grease, or oil.
- Fill any cracks, holes, or imperfections in the masonry with suitable filler material to create a uniform surface.
- Brush the surface to remove any loose particles and debris.
- Dampen the surface by spraying water until the surface is uniformly moist but not saturated. This helps to prevent the masonry from absorbing water from the plaster too quickly, which could lead to cracking.
- Setting Out Levels:
- Establish and mark reference points and levels using a plumb bob, spirit level, and chalk lines to ensure the plaster will be applied evenly.
- Fix temporary guide screeds at intervals on the wall to maintain the desired plaster thickness.
7. Mixing
- Mix Proportions:
- Use a mix ratio of 1:4 or 1:6 (cement:sand) by volume, depending on project specifications. A 1:4 ratio is typically used for external walls, while a 1:6 ratio may be sufficient for internal walls.
- Mixing Process:
- Place the sand in a clean mixing area or mixer, add cement, and mix dry until the color is uniform.
- Gradually add water while mixing until a workable consistency is achieved. The mix should be smooth and lump-free, with sufficient plasticity for application.
8. Application Procedure
- First Coat (Scratch Coat):
- Apply the first coat of plaster with a thickness of approximately 10 to 12 mm using a trowel. Start from the bottom and work upwards.
- Use a straight edge to ensure the surface is even and to remove excess material.
- While the plaster is still wet, create a rough texture by scratching the surface with a comb or toothed trowel. This “scratch coat” provides a key for the subsequent layers of plaster.
- Allow the scratch coat to cure for at least 24 hours, keeping it moist to prevent cracking.
- Second Coat (Finish Coat):
- Apply the second coat of plaster, typically 6 to 8 mm thick, over the cured scratch coat. Use a trowel to spread the plaster evenly and a straight edge to level the surface.
- Smooth the surface using a wooden float for a medium finish or a steel trowel for a finer finish, depending on the desired texture.
- For external applications, consider adding a waterproofing admixture to the finish coat as specified in the project documentation.
9. Finishing
- Final Smoothing:
- After the plaster has set slightly but is still workable, use a steel trowel to achieve a smooth finish.
- Optionally, use a sponge float to lightly dampen and smooth the surface, which will also help remove trowel marks and enhance the finish.
- Curing:
- Curing is essential to prevent the plaster from drying too quickly, which can cause cracking. Begin curing by gently spraying water on the plastered surface after 24 hours and continue curing for 7 days.
- Maintain the surface in a damp condition throughout the curing period to ensure the plaster develops sufficient strength and durability.
10. Quality Control
- Check for Thickness: Ensure the plaster is applied to the specified thickness, with uniformity across the entire surface.
- Surface Evenness: Use a straight edge and spirit level to verify that the surface is flat and free from undulations.
- Adhesion: Tap the surface to ensure the plaster has bonded well to the masonry without any hollow spots.
- Finish Quality: Inspect the final finish for smoothness, consistency, and absence of cracks or defects.
11. Clean-Up
- Clean all tools and equipment immediately after use to prevent cement from hardening on them.
- Remove any splashes or excess plaster from adjacent surfaces while it is still wet.
- Ensure the work area is clean and free from debris before leaving the site.
12. Completion & Handover
- Conduct a final inspection to confirm that the plastering work meets the required standards and specifications.
- Provide documentation confirming that the plastering is complete and ready for the next stage of construction, such as painting or finishing.
Conclusion
This method statement provides a clear and systematic approach to cement and sand plastering on masonry surfaces, ensuring that the work is carried out efficiently, safely, and to a high standard. Proper preparation, mixing, application, and curing are essential for achieving a durable and aesthetically pleasing plaster finish that will stand the test of time.
