Black lines left after a wash don’t always mean the crew skipped your gutters. Here’s how to tell the problems apart and what fixes each.

Two problems that look alike from the driveway

Tiger stripes are dark vertical streaks on the face of a gutter. A seller of tiger-stripe wipes says they form when rain runs off the roof carrying residue from asphalt shingles, leaf tannins and air pollution, then drips over the gutter’s front edge. One pro on a trade forum has seen stripes form on new homes within months where construction dust or heavy pollen was around.

Oxidation is the paint itself breaking down. A coil coating maker’s cleaning guide says all paints in direct sun slowly degrade, lose gloss and leave a powdery chalk. One gutter coil maker’s warranty says weathering will cause any colored surface to fade, darken, chalk or collect dirt and stains.

Older gutters often have both: faded, chalky paint with stripes on top.

Tiger stripes Oxidation (chalk)
What it looks like Dark vertical streaks on the gutter face Dull, faded paint; white or colored powder
Finger test Finger comes away mostly clean Powder comes off on your finger
Cause Roof runoff residue dripping over the edge Sun breaking down the paint
Standard house wash Usually leaves it Usually leaves it, unless blasted hard
What helps Detergent or a degreaser and a soft brush Mild soap and a soft brush, or an oxidation remover
Comes back? Yes, with runoff Yes, with sun
Who says so Alside gutter warranty care sheet; TigerStrike seller page; community discussion Dura Coat cleaning guide; Gutter Butter label; community discussion

Try the finger test

One pro on the forum uses this check: rub a fingertip along the gutter. Powder on your finger (white on a white gutter, brown or tan on a tan one) means oxidation. Black lines on a white gutter are tiger striping, not oxidation, the same pro says.

Why a standard house wash leaves both

A typical soft wash sprays a bleach-based mix at low pressure and rinses it off (our DIY soft wash guide explains the setup). The gutter coil maker’s own care sheet uses bleach for mildew. For stains from “chimney fumes, roof run-off,” it calls for detergent applied with a sponge or soft-bristled brush.

The tiger-stripe seller says soap and water, all-purpose cleaners and even pressure washing from below fail on stripes. A forum pro agrees, and adds that a house wash mix won’t take off oxidation either unless the gutter is blasted hard, which puts the paint at risk.

Scope matters too. One company’s price guide says a standard house wash covers “from the gutter line down” and lists gutter face brightening as an add-on. Another company’s rate card includes brightened gutter faces in its house wash. Read your quote line by line.

What removes tiger stripes

  • Start gentle. The gutter coil maker suggests a detergent solution (about 1/3 cup of laundry detergent per gallon of water), a sponge or soft brush and a thorough rinse.
  • Don’t scrub hard. The same care sheet says vigorous rubbing can leave glossy patches on the finish.
  • Step up carefully. A coating maker’s guide says large greasy areas may need a commercial grease remover. Forum pros mention degreasers diluted per the label and brushed on.
  • Avoid harsh stuff. That guide warns acid-based cleaners and high-phosphate detergents may damage the finish, and stiff or wire brushes do more harm than good. The gutter warranty doesn’t cover damage from harmful cleaning agents.

What removes oxidation, and what it can’t

Light chalk washes off with mild soap and a soft brush, the coating guide says. Heavier oxidation calls for its own product. One oxidation remover’s label gives a gutter brightening mix of 10:1 (17 oz per gallon). It says to wet nearby areas first, never let the product dry, test a hidden spot, use it above 50°F and keep it off polished aluminum.

No cleaner brings faded color back. The gutter warranty says fading and color change aren’t covered. A forum pro notes that removing oxidation doesn’t stop it from coming back. It’s the same lesson as chalky vinyl siding.

Why some areas see darker stripes

A washer in Pennsylvania wrote on the forum that many homes near him burn wood, coal or oil all winter. After an inversion, he said, the residue settles on gutters and fascia. He often tells homeowners it may only lighten.

A Pennsylvania DEP spokesperson explained that an inversion, a warm air layer above cooler air, traps pollutants close to the ground, including smoke from wood-burning fireplaces. The gutter maker’s care sheet also lists chimney fumes as a stain source.

What to ask before you book

  • Is gutter brightening included? One company’s sample estimate for a two-story home lists it as a $135 add-on. Our house washing cost guide shows what the base wash runs.
  • Which problem are you treating? Stripes, oxidation or both, and with what product?
  • Can you test one section first?
  • What will it look like in a year? Stripes return with runoff, and chalk returns with sun.

Our questions to ask a house washing company cover chemicals and rinsing. If something looks damaged afterward, see wash damage vs damage that was already there. For how we check facts, see our methodology.

Sources