What are tiger stripes on gutters?

Tiger stripes are dark vertical streaks or bands that appear on the face of aluminum gutters, usually running from the top edge downward. They form when ultraviolet light breaks down the protective coating on the metal, combined with dirt, mold, or mineral deposits that run down the gutter surface during rain. The pattern resembles stripes because water and debris follow the same paths repeatedly, creating distinct lines of discoloration against the lighter aluminum background.

These marks are purely cosmetic and do not affect gutter function or drainage. However, they become increasingly visible over time, particularly on light-colored gutters, and can make a home's exterior appear weathered or neglected. The streaks are most common in humid climates like Columbia, SC, where UV intensity and moisture levels both accelerate the oxidation process.

While tiger stripes cannot be prevented entirely, pressure washing can lighten or remove them temporarily. Many homeowners address them as part of routine gutter cleaning and brightening services to restore the gutter's appearance and improve overall curb appeal.