Poor Adhesion, Cracks, Rework? Master Cement Mortar Plastering Once and for All

 

Introduction | Why Cement Plastering Often Fails

In real construction projects, debonding, hollow spots, cracking, weak edges, and uneven color are among the most common plastering defects. In most cases, the issue is not the material itself, but poor substrate preparation, incorrect application sequence, excessive thickness, or insufficient curing.

This article provides a clear and practical guide to cement mortar plastering, covering different substrate types and key quality control points to help you achieve durable, defect-free results.

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1. Standard Plastering Workflow

Process Flow:
Joint sealing → Surface cleaning → Pre-wetting → Vertical alignment → Screeding → Base coat → Grid strips → Finish coat → Curing

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2. Plastering Techniques by Substrate Type

2.1 Concrete Substrates

Key Risk: Smooth surface leading to poor adhesion

Best Practices:

• Always roughen smooth concrete surfaces (mechanical or slurry bonding layer)

• Apply a reliable bonding layer before plastering

• Apply base coat in layers, each 5–7 mm thick

• Compact and finish the surface properly to reduce shrinkage cracks

Pro Tip:
👉 Plastering directly on smooth concrete almost guarantees hollowing.

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2.2 AAC / Lightweight Concrete Blocks

Key Risk: High water absorption and low strength

Best Practices:

• Thoroughly pre-wet the surface (minimum 10 mm penetration)

• Repair damaged edges before overall slurry spraying

• Apply base coat in multiple compacted layers

• Control finish coat color consistency

Pro Tip:
👉 Insufficient pre-wetting leads to cracking.

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2.3 Brick Walls

Key Risk: Uneven suction at mortar joints

Best Practices:

• Clean joints and remove loose dust

• Pre-wet evenly before plastering

• Use screeds to control flatness

• Strictly control water-to-cement ratio

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3. Cold and Wet Weather Construction

• Plastering temperature should not fall below 5°C

• Fresh mortar must not freeze during early curing

• Chloride additives are not allowed for painted surfaces

• Frozen masonry must be fully thawed before plastering

Key Reminder:
👉 Winter plastering is about stability, not speed.

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4. Quality Acceptance Criteria

• Materials must meet design requirements

• Strong adhesion between layers and substrate

• No hollowing, delamination, or structural cracking

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Conclusion | Plastering Is a Technical Process

High-quality cement plastering depends on process control, proper execution, and attention to detail. With the right preparation and curing, most common defects can be effectively avoided.

👉 One successful application is better than repeated repairs.