18/05/2026
SUCCESS FACILITIES AND GENERAL ENGINEERING LTD
WHY PLASTER CRACKS IN CONSTRUCTION AND CIVIL ENGINEERING WORKS
Plaster cracks typically appear after a short period due to material shrinkage, rapid moisture loss, temperature fluctuations, or structural settlement.
Plaster has a low tensile strength; any stress from drying or moving materials can easily cause the surface to crack.
The most common engineering and construction causes of this defect include:
1. Material Shrinkage & Rapid Drying / Improper Mixing Ratios
Using too much cement or water creates a “rich” mix that undergoes severe volume reduction (shrinkage) as it dries.
- Rapid Evaporation: If plaster dries too quickly—such as in direct sunlight or strong winds—it loses moisture before developing chemical strength, resulting in map or hairline cracks.
- Dirty Sand: Sand containing high amounts of clay, silt, or organic impurities weakens the mortar-to-brick bond and shrinks significantly when it dries.
2. Poor Workmanship and Ex*****on / Inadequate Curing
Cement plaster requires moisture to cure and gain strength. Failing to spray water on the plastered walls for at least 7 to 10 days accelerates drying and triggers cracking.
- Excessive Thickness: Applying plaster in one thick coat (over 15 mm) instead of multiple thin layers leads to uneven internal stresses and cracking as the thicker section shrinks.
- Poor Surface Preparation: Failing to clean dust, oil, or loose mortar off the base masonry prevents a strong mechanical key or bond, causing hollow cracks or delamination.
3. Structural & Environmental Movements / Joints Between Different Materials
The junction where brickwork meets concrete elements (columns and beams) expands and contracts at different rates due to temperature shifts.
Without embedded wire mesh (chicken mesh) to absorb these stresses, vertical cracks form at the joints.
- Building Settlement & Expansion: New buildings naturally experience minor soil settlement or moisture-related expansion of clay bricks in their first few months, transferring stress to the rigid plastered layer.
- Vibrations & Expansion: Heavy traffic, passing trains, or seasonal weather variations induce vibrations and thermal expansion that crack unreinforced or aged plaster.
Key Mitigation Tips
1. Use Mesh
Always use chicken wire mesh at RCC-brick junctions, electrical chasing, and plumbing lines.
2. Proper Curing
Keep the plaster moist for at least 7 days to slow drying.
3. Proper Mix
Stick to a 1:4 or 1:5 cement–sand ratio for plastering.
4. Dampen Surfaces
Thoroughly wet the masonry surface before applying plaster.
5. Thin Coats
Apply plaster in layers rather than one thick layer.
