With painted wood siding, peeling occurs when moisture in the siding is drawn from the wood by the sun's heat and pushes the paint from the surface. What causes the peeling?

• A. Moisture
• B. UV exposure
• C. Lack of primer
• D. Abrasion from wind

Answer: (A)

Moisture moving within the wood and building pressure under the paint is what causes the peeling here. When sunlight heats the siding, water inside the wood warms up and tends to migrate toward the surface. The paint film sits on top, and the moisture that reaches the interface creates vapor pressure beneath the coating. That pressure pushes the paint away from the wood and weakens the bond, so the film starts to lift and peel away. This is especially common with painted wood siding because the paint acts as a barrier to moisture escape, enabling blistering and peeling as the moisture tries to escape.

UV exposure and lack of primer can contribute to other paint problems (fading or poor initial adhesion, respectively), but the mechanism described—moisture being drawn to the surface by heat and causing the paint to push away from the wood—points to moisture as the main cause. Abrasion from wind would wear away paint rather than specifically producing this moisture-driven peeling.