Can they just be pressure washed?

Not without voiding one maker's warranty. The one gutter maker's care instructions we could read recommend, for tiger striping, clear water from a garden hose and a soft-bristled brush, and state that high pressure spraying will void the warranty. If your gutters carry that warranty, anyone offering to blast the stripes off is offering you a method that costs it.

Will they look new again?

Better is the realistic expectation. New is a different promise, and we do not make it. Brightening takes soil off, and soil is what the stripes are. It does not reverse a chalked or faded finish, which the one gutter maker's warranty we could read says exposure to the elements may cause, and it does nothing for corrosion in the metal. We look at the gutters up close before quoting so you hear which of those you have before the work rather than after it.

What causes tiger striping?

We found no manufacturer document that settles it, and this page says so rather than invent one. The single manufacturer document that names the condition calls it atmospheric soil accumulation and stops there. No cause is given in any manufacturer document we could read. What that document does give is the procedure: clear water, a garden hose and a soft-bristled brush.

Is this the same as gutter cleaning?

No. They are two jobs, and a house can need either or both. Gutter cleaning is the trough: clearing what has collected in it so the water goes where it was meant to go, which is what protects the walls. Brightening is the front face, the part you see from the street. When both are booked, that is the order that makes sense, so nothing comes out of the trough and runs down a face that has just been finished.

Gutter brightening (tiger striping)

Look along the face of a gutter in good light and you may find dark vertical bands, fairly evenly spaced, on a house whose walls look clean. The one gutter maker's document we could read calls them soil, leaves them out of its finish warranty, recommends washing them with a garden hose and a soft-bristled brush, and says high pressure spraying will void the warranty. We do this work by hand, with a soft or medium bristle brush and a chemical solution that removes oxidation — and there are things it cannot put back.

What the stripes are, and what we cannot tell you

It is called tiger striping. The one manufacturer document we can find that names it — Norandex's aluminum gutter warranty — defines it as atmospheric soil accumulation, calls it naturally occurring, and excludes it from the finish warranty. Two useful things follow. The first is that it is dirt in the ordinary sense: something that arrived out of the air and stayed. The second is that this is probably not a warranty claim: the one maker whose warranty we could read has already written it down as maintenance rather than a defect in the coating. What this page will not do is tell you why it lands in stripes instead of evenly. We found no settled answer. The manufacturer document that names the condition offers no mechanism at all — only the term and the exclusion. We found no manufacturer document that gives a cause, so we do not print one. This page has a hole in it where the cause should be, and we would rather you saw the hole. What that maker recommends for taking the stripes off does not depend on where they came from.

What one maker's instructions say about pressure

The one gutter maker's care instructions we could read put tiger striping first among the cleaning procedures they recommend, and the procedure is short: wash with clear water, using a garden hose and a soft-bristled brush. They add that a long-handled car-washing brush is ideal for the purpose and, in the same note, that high pressure spraying will void the warranty. That is the warranty the maker wrote for its own aluminum gutter system, so if yours came from that maker, high pressure on them costs you that warranty. The same instructions say excessive scrubbing is unnecessary and can be harmful to the product.

Why the gutter line is still dirty after the house is clean

That maker's care instructions say where to look: particular attention should be given to areas under eaves, porches, awnings and other overhangs that have limited exposure to the natural washing effect of rainfall. Rain rinses a wall every time a storm comes through. It does not rinse the strip tucked up under the eave, and it does not rinse the underside of anything. The procedure that maker recommends for the striping is clear water, a garden hose and a soft-bristled brush. Where a sodium hypochlorite solution has been used above — a roof, a wall — the gutters come into it: the label of an EPA-registered product says to rinse quickly and thoroughly if the solution comes in contact with aluminum window frames or gutters, since metal corrosion may occur. Everything that comes off a roof arrives at the gutter, and it should not sit there.

What brightening cannot undo

The same warranty puts chalking, fading and soiling in one list, with tree sap and staining, as changes in surface colour that exposure to the elements may cause. Soiling comes off. Fading does not, and a finish that has chalked does not get its colour back. A chalked finish, the kind that leaves a dark cloth powdered when you run it along the gutter, has changed at the surface, and washing it does not bring the colour back; it takes the dirt off something that is already dull. A run that has faded unevenly under years of Florida sun stays faded. Corrosion is the third one. The same warranty says that direct contact of aluminum with certain dissimilar materials, or contact with the water running off them, is likely to result in corrosion, so where a gutter has been sitting against something it should not have been, the mark is in the metal — and cleaning the face around it can make it easier to see rather than harder. None of that is a reason to leave the gutters as they are. The aim is a face that comes back far enough that you stop noticing it from the street. But which of the three you have takes a look up close; ask us for one, or send photos, before anyone promises you bright metal from the driveway. The 14-day workmanship warranty covers this service. It cannot cover a finish the weather already took.

Common questions

Can they just be pressure washed?: Not without voiding one maker's warranty. The one gutter maker's care instructions we could read recommend, for tiger striping, clear water from a garden hose and a soft-bristled brush, and state that high pressure spraying will void the warranty. If your gutters carry that warranty, anyone offering to blast the stripes off is offering you a method that costs it.
Will they look new again?: Better is the realistic expectation. New is a different promise, and we do not make it. Brightening takes soil off, and soil is what the stripes are. It does not reverse a chalked or faded finish, which the one gutter maker's warranty we could read says exposure to the elements may cause, and it does nothing for corrosion in the metal. We look at the gutters up close before quoting so you hear which of those you have before the work rather than after it.
What causes tiger striping?: We found no manufacturer document that settles it, and this page says so rather than invent one. The single manufacturer document that names the condition calls it atmospheric soil accumulation and stops there. No cause is given in any manufacturer document we could read. What that document does give is the procedure: clear water, a garden hose and a soft-bristled brush.
Is this the same as gutter cleaning?: No. They are two jobs, and a house can need either or both. Gutter cleaning is the trough: clearing what has collected in it so the water goes where it was meant to go, which is what protects the walls. Brightening is the front face, the part you see from the street. When both are booked, that is the order that makes sense, so nothing comes out of the trough and runs down a face that has just been finished.

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