What causes paint to peel?

Paint peeling is primarily caused by poor adhesion between the paint and the surface underneath, which happens when moisture gets behind the paint film or when the surface wasn't properly prepared before painting.

The most common culprit in Ottawa homes is moisture infiltration. This can come from several sources: high humidity levels (especially in bathrooms and kitchens), water leaks from plumbing or roofing, or exterior moisture penetrating through siding or around windows. When moisture gets trapped behind paint, it breaks the bond between the paint and the surface, causing the paint to lift and peel away in sheets or flakes.

Surface preparation issues are equally problematic. If the previous paint was glossy and wasn't properly sanded or primed, the new paint can't grip properly. Similarly, painting over dirt, grease, or chalky surfaces creates a weak foundation that will eventually fail. Many Ottawa homeowners discover peeling paint when they try to paint over old oil-based paints with latex paint without using a proper bonding primer.

Temperature and humidity fluctuations are particularly challenging in Ottawa's climate. Our extreme temperature swings from -30°C winters to +35°C summers cause building materials to expand and contract repeatedly. This movement can stress paint films, especially on exterior surfaces like siding, trim, and decks. Interior rooms with poor ventilation, such as basements or bathrooms without proper exhaust fans, create conditions where paint is more likely to fail.

Age and quality of materials also play a role. Cheaper paints or those applied too thinly may not have the flexibility to handle normal building movement. Lead-based paints common in Ottawa homes built before 1978 become brittle over time and are more prone to peeling, though these require special handling due to health concerns.

For exterior peeling, check for clogged gutters, damaged caulking around windows and doors, or siding issues that allow water penetration. Interior peeling often indicates ventilation problems or hidden moisture sources like leaking pipes in walls.

Professional assessment is recommended when peeling is widespread, occurs in multiple rooms, or if you suspect lead paint in pre-1978 homes. A qualified painter can identify the root cause and recommend proper surface preparation, primer selection, and paint systems that will perform well in Ottawa's challenging climate. Addressing only the symptoms without fixing the underlying moisture or adhesion issues will result in the problem returning within a year or two.