Elastomeric coatings are applied to roofs, walls, and structural surfaces for their flexibility, waterproofing, and UV resistance. Elastomeric polyurethanes bridge cracks and waterproof substrates like concrete and metal. When properly installed, these coatings provide long-term protection and durability. However, defects can occur if surface preparation, application, or environmental conditions are not controlled.

Understanding these defects and how to prevent them is essential for contractors, inspectors, and asset owners. The following outlines common elastomeric coating defects, their causes, and prevention methods.

1. Cracking and Crazing

Description
Cracking refers to visible breaks in the coating film, while crazing appears as fine, spider‑web‑like cracks.

Common Causes

• Insufficient coating thickness
• Application over substrates with active movement
• Poor-quality or aged coating materials
• Application during extreme temperatures

Prevention Solutions

• Apply the coating at the manufacturer’s recommended dry film thickness
• Use elastomeric products formulated for high elongation and movement
• Ensure substrates are structurally sound and stabilized before coating
• Avoid application in very cold or excessively hot conditions
• Mix products according to manufacturer instructions

2. Blistering

Description
Blistering appears as raised bubbles beneath the coating surface and can eventually cause coating failure.

Common Causes

• Poor surface preparation resulting in poor adhesion
• Moisture trapped beneath the coating
• Application over damp or insufficiently cured substrates
• Outgassing from concrete or roofing materials
• Applying coating during high humidity or direct sunlight

Prevention Solutions

• Allow substrates to dry and cure fully before coating
• Test for moisture vapor transmission, especially on concrete
• Apply coatings when the substrate temperature is declining and at least 5°F (3°C) above the dew point
• Use primers where moisture vapor is a concern
• Prepare surfaces according to manufacturer’s instructions.

3. Peeling and Delamination

Description
Peeling occurs when the coating loses adhesion and separates from the substrate as sheets or flakes.

Common Causes

• Poor surface preparation
• Presence of dust, oil, rust, or old failing coatings
• Incompatible primer or substrate
• Missed recoat window time between coats

Prevention Solutions

• Clean surfaces thoroughly using pressure washing or abrasive methods as needed to achieve the specified surface profile
• Remove loose or deteriorated existing coatings
• Use primers recommended by the coating manufacturer
• Follow the specified recoat and curing times strictly

4. Pinholing

Description
Pinholes are tiny holes in the coating that can allow water intrusion.

Common Causes

• Entrapped air in porous substrates
• Rolling or spraying too aggressively
• Application over rough or highly porous surfaces
• Low coating viscosity
• Application over contaminated surfaces

Prevention Solutions

• Seal porous substrates with appropriate primers or fillers
• Apply coatings evenly using proper tools and techniques
• Avoid overworking the coating during application
• Use multiple coats if necessary to achieve full coverage
• Apply products to clean, dry and properly prepared surfaces

5. Alligatoring (Mud Cracking)

Description
Alligatoring resembles reptile skin and indicates significant film stress or aging.

Common Causes

• Excessively thick single-coat application
• Poor-quality or incompatible coatings
• Aging and UV degradation
• Applying rigid coatings above flexible materials
• Improper mixing
• Exposure to chemicals

Prevention Solutions

• Apply multiple thin coats instead of one thick coat
• Use compatible coating systems throughout
• Select UV‑resistant elastomeric products for exposed surfaces
• Avoid mixing coating types unless approved by the manufacturer

6. Incomplete Curing

Description
The coating remains soft, tacky, or weak long after application.

Common Causes

• Application outside the recommended temperature range
• High humidity or rainfall during curing
• Incorrect mixed ratios
• Excessive coating thickness
• Poor air circulation

Prevention Solutions

• Monitor weather conditions carefully before and after application
• Apply coatings within specified temperature and humidity limits
• Follow manufacturer guidelines for thickness per coat
• Ensure adequate ventilation during curing

Final Thoughts

Most elastomeric coating defects are preventable with proper planning, material selection, and quality control. Surface preparation, environmental awareness, and strict adherence to manufacturer instructions form the foundation of any successful coating system.

By identifying early signs of defects and applying preventative measures, owners and contractors can extend the life of elastomeric coatings and protect their investments from premature failure.