Paint Defects & Troubleshooting

Paint Peeling

The exam asks: What causes paint to peel? The answer is poor surface preparation or moisture issues. Peeling is the most common paint failure and almost always traces back to one of these two root causes.

Poor surface preparation causes peeling when:

• Paint is applied over dirty, greasy, or chalky surfaces
• The surface was not properly sanded or deglossed
• Primer was skipped on bare substrates
• Incompatible paint systems were layered (e.g., latex over uncured oil)

Moisture issues cause peeling when:

• Water vapor migrates through walls from interior humidity
• Exterior water infiltrates through gaps in siding or flashing
• Condensation forms between the paint film and substrate
• Bathroom or kitchen exhaust systems are inadequate

Paint Blistering

Paint blistering is caused by moisture trapped under the paint film. Blisters are bubble-like raised areas in the paint surface that contain either moisture or air. There are two types:

• Moisture blisters - caused by water vapor trapped beneath the film. These blisters typically contain liquid when punctured. The solution is to fix the moisture source before repainting.
• Heat blisters - caused by painting in direct sunlight or on surfaces that are too hot. Solvent vapor cannot escape through the rapidly dried surface film. These blisters are typically dry when punctured.

Paint peeling is caused by poor surface preparation or moisture issues. Blistering is caused by moisture trapped under the paint film. Always diagnose and fix the root cause before repainting - simply painting over the failure will result in the same defect recurring.