Why Plastering Is More Than Decoration

Plastering isn’t just about aesthetics—it protects your structure, ensures smooth finishes, and prevents cracks.

During the Kempinski Gold Coast Project, I noticed common plastering mistakes: uneven walls, poor bonding, and cracks caused by wrong materials or poor technique. With careful observation and experimentation, I found methods that work best for tropical climates like Ghana.

1. Use the Right Materials

Material quality is the foundation of good plastering.

• Sand: Avoid high NaCl (salt) content—it causes efflorescence and cracks.

• Water: Use clean, potable water. Contaminated water reduces bond strength.

Tip: Test your sand and water before large-scale plastering.

2. Mixing Ratios Matter

Cement-to-sand ratios affect plaster strength and durability:

Climate / Area Cement per 1 m³ Sand Standard 350 kg Humid areas 400 kg Hot climates 450 kg

On-site trials in Ghana showed 450 kg per m³ of sand produced the strongest, crack-free plaster.

Tip: Mix small samples and monitor for 7 days before full-scale application.

3. Timing Is Critical

• Use plaster within 1.5 hours of mixing.

• Waiting longer reduces bonding and increases cracking risk.

4. Linking Concrete and Masonry

Correct bonding prevents future cracks:

• Galvanized steel mesh corrodes → cracks

• Fiber reinforcement is safer and durable.

5. Surface Preparation – Scratch Coat

Surface prep ensures plaster sticks:

1. Clean walls: Remove dust, debris, and loose wood

2. Cure walls with water

3. Spray coat (scratch coat):

   • 1 bag cement + 1 wheelbarrow sand covers ~40 m²

   • Use a bucket, not the ground

4. Concrete surfaces: Hack or sandblast to improve adhesion

5. Bonding agent (optional): e.g., Sika Latex 107.

6. Setting Grid Lines

Accurate grids ensure:

• Straight walls

• Squared rooms

• Correct building orientation

How to do it:

• Use a plumb bob for main axes

• Check 90-degree angles (3:4:5 rule)

• Transfer axes to all floors.

7. Plaster Guides (Screeds)

Guides define wall thickness and uniformity:

• Use cement guides only; gypsum causes cracks

• Vertical guide every 2 m

• Horizontal guide: 2 per 3 m height

• Recommended thickness:

  • Walls: 2–2.5 cm

  • Ceilings / slabs: 1.5–2 cm

8. Quality Control During Application

• Use a straight edge on the wall

• Shine light behind it → check for uneven pressure

• Correct uneven areas immediately

Tip: Proper application avoids painting defects and false ceiling alignment problems.

9. Final Curing

Curing is essential for strength and durability:

• Keep walls damp for several days

• Prevent cracks and surface shrinkage.

Key Takeaways

Plastering is engineering, not just decoration. By using:

• Proper materials

• Accurate mixing ratios

• Careful surface preparation

• Precise grids and guides

• Adequate curing

…you can achieve crack-free, durable, and smooth plaster even in challenging climates.

• Author name: Ali Omar

• Job title: Civil Engineer / Project Manager

•  LinkedIn URL:www.linkedin.com/in/ali1omar