The Real Causes of Cracks in ETICS – 90% of Failures Start at the Very Beginning
Created on 01.13
❌ Cracks Appearing on the Rendering Layer?
In ETICS, most failures start long before construction
Cracking of the rendering layer is one of the most common and costly problems in External Thermal Insulation Composite Systems (ETICS).
Cracks not only affect façade appearance but also reduce thermal performance and increase the risk of debonding or detachment.
In practice, rendering cracks are rarely caused by a single mistake—they are the result of system imbalance.
I. Main Causes of Rendering Cracks
1. Material Issues
- Low-density insulation boards (<18 kg/m³) deform easily
- Insufficient aging time, leading to post-installation shrinkage
- Excessive cement content causing high shrinkage
- Inferior alkali-resistant fiberglass mesh
2. Design Deficiencies
- Lack of stress-release structures
- Incompatible elastic modulus between system layers
- Insufficient expansion joints
3. Construction & Environmental Factors
- Excessive single-layer thickness
- Incorrect mesh placement
- Application under extreme heat, sunlight, or wind
- Insufficient curing
- Thermal movement, aging, and structural deformation
II. Systematic Solutions
Material Control
- Insulation density:
18–22 kg/m³, with sufficient aging
- Optimized mortar formulation with controlled cement content
- Use of
redispersible polymer powder (RDP) to improve flexibility
- Certified alkali-resistant fiberglass mesh
System Design
- Core principle:
gradual stress transition and flexible stress release
- Proper expansion joints and reinforced critical areas
Application Control
- Layered application and correct mesh embedding
- Avoid extreme weather conditions
- Proper curing for at least
5–7 days
Conclusion
Rendering cracks are not accidental—they are systematic failures.
Only by controlling materials, design, and application as one system can long-term crack resistance be achieved.
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