Plastering is a crucial step in construction, ensuring both the protection and aesthetic appeal of a structure. It involves applying a layer of cement or lime mortar over masonry surfaces, which safeguards against environmental damage and enhances the overall look of a building. Additionally, proper plastering improves hygiene by creating a smooth, washable surface.

In this blog, we’ll explore the general specifications of plastering, its process, and relevant Indian Standards (IS codes) to ensure the highest quality of work.

Why Is Plastering Important?

Plastering serves several essential purposes:

• Protection: Shields masonry and concrete surfaces from weathering, moisture, and mechanical damage.
• Aesthetic Enhancement: Provides a smooth, even surface for paint or decorative finishes.
• Hygiene Improvement: Creates washable, dust-free walls, reducing allergen accumulation.
• Durability: Prolongs the life of masonry by preventing cracks and seepage.

General Specification of Plastering

1. Surface Preparation

• Masonry walls must be cleaned of dust, dirt, and grease.
• Raking the joints to a depth of 10-15 mm enhances the bond between the plaster and masonry.
• The surface must be moistened with water for at least 24 hours before starting the plastering process.

2. Plastering Mortar

• The mortar used in plastering is typically a mix of cement and sand in various ratios:
  • 1:3 for external surfaces exposed to severe weather.
  • 1:4 or 1:6 for internal walls and ceilings.
• High-quality, well-graded sand must be free from organic impurities to ensure a durable mix.

3. Thickness of Plaster

• The thickness of plaster depends on its application:
  • 12–15 mm for internal walls.
  • 15–20 mm for external walls.
  • 6–8 mm for ceilings.
• Layers thicker than 20 mm should be avoided to prevent cracking.

4. Reference Marks (Bundas)

• Reference points or bundas should be created on the wall surface using mortar before plastering begins.
• These ensure that the plastering is uniform and in a straight line, aligned with levels and plumb lines.

5. Alignments and Joints

• Plastered surfaces must be perfectly straight, levelled, and plumbed.
• Joints should form clean, right angles, ensuring no irregularities in the finished surface.

6. Pre-Installation of Fixtures

• Fixtures such as door and window frames, water supply lines, and electrical fittings must be installed before plastering.
• Plastering around these elements should be neat, with excess mortar removed immediately.

7. Application Process

a. Scratch Coat

• The first coat of plaster, about 9–12 mm thick, is applied and scratched to create a rough texture. This improves bonding with the final coat.

b. Finish Coat

• The second coat, thinner than the first (3–5 mm), is applied to achieve a smooth and polished surface.

8. Curing

• Proper curing of the plastered surface is essential to achieve strength and durability.
• The surface should be cured with water for a minimum of 7 days, ensuring proper hydration of the cement.

Common Issues and Solutions in Plastering

1. Cracking:
   • Cause: Improper curing or excessive thickness.
   • Solution: Ensure adequate curing and apply plaster in thin, even layers.
2. Efflorescence:
   • Cause: Presence of salts in water or sand.
   • Solution: Use potable water and purified sand as per IS 1542:1992.
3. Bond Failure:
   • Cause: Poor surface preparation.
   • Solution: Thoroughly clean and rake the surface before applying plaster.

IS Codes for Plastering

Several Indian Standards provide guidelines for achieving high-quality plastering:

• IS 1661:1972: Code of practice for applying cement plaster to masonry.
• IS 2402:1963: Recommendations for surface preparation and plaster application.
• IS 1542:1992: Specification for sand used in cement mortar for plastering.
• IS 456:2000: General guidelines for curing cement-based work.

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Tips for High-Quality Plastering

• Use Quality Materials: Ensure that cement, sand, and water meet the relevant IS standards.
• Plan Ahead: Pre-install all fixtures and fittings before starting plastering.
• Ensure Consistency: Mix mortar in small batches to avoid setting before application.
• Regular Curing: Curing prevents cracks and enhances the plaster’s strength.

Conclusion🎯

Plastering is an integral part of construction that protects and beautifies a building. By following standard practices, adhering to IS codes, and using quality materials, you can achieve durable and aesthetically pleasing plastered surfaces. Whether safeguarding the structure or preparing it for finishing, proper plastering ensures the longevity and visual appeal of any project.