Tiger Striping on Eavestroughs – Causes and Prevention in Ottawa

Tiger striping refers to the dark vertical streaks that develop on the outside face of eavestroughs over time, giving them a striped appearance that resembles tiger markings. It is one of the most common cosmetic complaints Ottawa homeowners have about their gutters, and while it does not affect eavestrough performance, it can make an otherwise well-maintained home look neglected.

What Causes Those Dark Streaks

Tiger striping is caused by a chemical reaction between the eavestrough's painted surface, airborne pollutants, and electrostatic bonding. As water overflows or drips down the outside of your gutters, it carries dissolved asphalt particles from your shingles, dirt, pollen, oxidized aluminum, and atmospheric pollutants. These contaminants bond electrostatically to the eavestrough's baked enamel coating, forming streaks that follow the water's path. Ottawa's environment is particularly conducive to tiger striping because our heavy spring pollen season (especially from the abundant maple and oak canopy), combined with winter road salt residue that becomes airborne, provides a steady supply of bonding contaminants.

The streaks are not surface dirt — they are chemically bonded to the paint, which is why a simple garden hose or even pressure washing rarely removes them. The longer tiger striping remains, the deeper the bond becomes and the harder it is to remove.

To clean existing tiger stripes, you need a product specifically designed to break the electrostatic bond. Products like Krud Kutter, Gutter Zap, or Gutter Butter are available at Ottawa building supply stores and work well when applied with a soft cloth or non-abrasive pad. Work in small sections, applying the cleaner, letting it dwell for 30 to 60 seconds, then wiping firmly in the direction of the streaks. A single-storey bungalow is a reasonable DIY project — budget about $20 to $40 in cleaning products and a few hours of work. For two-storey homes, professional cleaning is safer and typically costs $200 to $450 in Ottawa depending on the linear footage.

Never use abrasive pads, steel wool, or harsh solvents like acetone on painted aluminum eavestroughs. These will strip the factory baked-enamel finish and actually accelerate future staining by exposing bare aluminum to oxidation. Also avoid pressure washing at close range, which can dent aluminum gutters and force water behind the fascia board.

To prevent tiger striping from returning quickly, address the root causes. Ensure your eavestroughs have proper slope — pooling water that overflows the front edge is the primary source of the dripping that creates streaks. Your gutters should slope at least one quarter inch per 10 feet toward the nearest downspout. Keeping eavestroughs clean and free-flowing with twice-annual cleaning reduces overflow incidents. Installing gutter guards at $10 to $25 per linear foot dramatically reduces debris buildup and the associated overflow that feeds tiger striping.

Some Ottawa homeowners apply a car wax or UV-protectant spray to the exterior of clean eavestroughs after removing tiger stripes. This creates a slicker surface that resists contaminant bonding and makes future cleaning easier. Reapply annually in spring for best results. If your eavestroughs are heavily striped and you are considering full replacement, a professional eavestrough installer can discuss options — browse contractors through the Ottawa Construction Network directory at justynrookcontracting.com.