Rain and Tiger Striping and Gutters! Oh My!

Tiger striping occurs on a variety of metal surfaces with painted finishes, such as cars, motor homes, siding, roofs, and gutters. The cause for the unsightly black streaks that form on the outside of a gutter is sometimes blamed on the paint turning a different colour. But tiger stripes on gutters are actually the result of moisture on the top lip of the gutter interacting with pollutants, dirt, and asphalt shingles residue. When droplets become large enough to run down the front of the gutter, streaks appear.

Where You Live

Whether you experience extensive or occasional tiger striping depends on where you live, the amount of rain that falls and how much humidity. For example, expect to see more tiger stripes if you live in a region with high humidity or an area populated by factories. Other determining factors include the presence of medium to high levels of pollutants in the air like industrial chemicals, pesticides and smoke and organic substances such as soil and tree sap.

Darker the Streaks

Dark vertical streaking on the face of your gutters is a sign that the tiger striping process has been going on for some time. The darker the streaks, the more build-up there is to deal with. When tiger striping is really noticeable, it can detract from the cared-for appearance of your home’s exterior. More importantly, while it might seem like a matter of aesthetics, the longer tiger striping is left unattended the more potential damage it can do to the finish of your gutter system.

Removing Tiger Striping

The darker the tiger stripes mean they will generally be harder to remove than if they are lighter in colour. A heavy duty cleaner, one formulated to remove deep-seated stains but is not harsh or abrasive, might be required and several applications needed before the surface is thoroughly cleaned. Lighter tiger stripes or striping that includes mold or mildew can usually be removed with a solution of laundry detergent, bleach, and water.


The good news is tiger striping’s preventable. Since the process is caused by the buildup of pollutants and material deposits, annually washing away surface grime and stains can prevent discolored streaking from occurring.