Black Streaks on the Outside of Gutters ("Tiger Stripes")

What tiger stripes are

Tiger stripes are the dark vertical streaks you see on the outside face of aluminum or vinyl gutters. They often line up with where water spills over the lip. They look like dirt, but they behave differently. A hose does nothing, and even a normal house wash often leaves them behind.

The streaks form when dirt, soot and pollution in rainwater run over the gutter edge and cling to the painted finish. Over time, that grime bonds to the surface through a mild electrostatic and chemical attraction. The result is a film that has to be broken down, not just rinsed off.

You will usually see them first on the front of the house, where the gutters face the street and the morning sun. Once a house wash makes the walls bright, the stripes stand out even more.

Why they keep coming back

Gutters overflow when they are clogged. Water that should flow to the downspout spills over the front edge, carrying roof grit and decomposing leaves with it. Each overflow lays down another thin layer. Heavy leaf drop, palm debris and Santa Ana wind events make clogs more likely in LA.

Oxidation plays a role too. Painted aluminum gutters break down slowly in strong sun, and a chalky, weathered finish holds onto grime more easily than a fresh one. That is why older gutters on sunny sides of the house often show the worst striping.

Why normal washing misses them

A standard soft wash is designed to remove organic growth and general dirt from walls. Tiger stripes are a different kind of soil. The house-wash solution may lighten them a little, but the film usually stays.

Turning up the pressure is the wrong fix. High pressure on gutters can dent them, push water behind the gutter into the fascia, and strip already-weak paint, leaving a patchy look that is worse than the stripes.

Some people try magic erasers or kitchen scrub pads. They can work on small spots, but they are mildly abrasive and can leave dull patches on painted aluminum that look worse in full sun than the stripes did.

How tiger stripes are actually removed

Removal takes a dedicated gutter-face or tiger stripe cleaner, the kind formulated to break the bond between grime and the painted finish. It is applied to the outside face of the gutter, given a short dwell time, and agitated lightly with a soft brush or microfiber pad on a pole. Then the face is rinsed with low pressure.

Some stripes come off in one pass. Older, heavier ones may need a second application. On badly oxidized gutters, expect the stripes to lighten a lot but possibly leave a faint shadow, because the paint itself has changed. At that point, painting or replacing gutters is the only way to get a like-new face.

Test any cleaner in a small, out-of-the-way spot first. Avoid abrasive pads and harsh solvents, which can dull or remove the finish.

Fix the cause: clean the gutters too

Cleaning the outside of a clogged gutter is a short-term fix. The next rain will overflow and start a new set of stripes. It makes sense to clean the inside of the gutters and clear the downspouts at the same visit, ideally before the rainy season begins around November.

Gutter cleaning is $1.25 per linear foot as of October 2026, as our gutter cleaning cost guide explains. If you are also washing the house at $0.35 per square foot of wall, booking both together earns a 5% bundle discount, or 10% with a third service. Every visit has a $195 minimum.

What to expect from a professional visit

When Say Wash It handles tiger stripes, we clean out the gutters first, then treat and gently scrub the outside faces, and rinse the walls below so no runoff streaks are left behind. We will tell you up front if oxidation means the stripes are likely to lighten rather than disappear completely.

Between cleanings, keeping gutters clear is the best prevention. Gutter guards can help in yards with heavy leaf drop, though they still need occasional checks. The instant quote on this page can price gutter and house cleaning together so you see the flat number before booking.