Tiger Striping on Gutters: Ajax Pressure Washing

how to remove black marks from eaves

Yet another post about my obsession (apparently), nice clean eaves/gutters!

This was an issue that I just faced.  I recently did pressure washing and window cleaning on a bungalow in South Ajax.  When I first inspected the home in Ajax for a quote on pressure washing and window cleaning, I saw black streaks on the outside of the eaves.

This is called “Tiger Striping.”  And it does not wash off.  Regardless of how much PSI or GPMs your pressure washer has, you will not remove these black stains.

Scrubbing the eaves may improve their appearance, but they do not go away.

You may want to zoom in on the picture above to get a good look at the black lines that are on the outside of the eaves.  This is an extremely common issue.

Let’s start at the beginning:

“What is Tiger Striping?”

gutter zap tiger stripes

What we call Tiger Striping is a vertical black staining on the exterior of eaves.  Many home owners in Ajax, hire pressure washing companies or window cleaners to wash their eaves and expect the black stains to simply wash away.  But, when the black lines remain, it is disappointing.

getting black streaks off of gutters

Put simply, the reason that Tiger Stripes can’t be simply washed off is because of Oxidization.  This happens over time when the top layer paint is no longer smooth and attracts dirt, pollution, tar from the roof and other contaminants.  Because of the oxidization, the contaminants become part of this layer.

ajax window cleaning

Removing oxidization is risky and very temporary.  The stains will return quickly.  After our standard pressure wash and window clean, if black stains remain on the gutters, we recommend having the eaves re-painted.

how to use gutter zap

Don’t replace your gutters if they are functioning correctly.  Save your money.  When repainted by a professional, the eaves or gutters look like they are brand new!  A house wash is a necessary step in paint prep.

So, what do we do when confronted with Tiger Striping?  Put simply, we aim to improve the appearance, but we no longer try to completely remove them.  Clean siding and clean eaves are the goal of every house wash.  However, when paint has become Oxidized, (which always happens over time) it is an issue that cannot be solved with a pressure washer or chemicals.

How do I know if my paint has oxidized?  If you run your finger over the surface of the paint, and a chalky powder is on your finger, your paint is oxidized.

What about chemicals or scrub pads that advertise removal of Tiger Striping?


Any product that can remove Tiger Striping will remove the oxidized paint in the process.  This is very dangerous because it can result in partial or complete removal of paint from the eaves.

The bottom line is that when Tiger Stripes are visible, the paint has very likely reached the end of it’s life span.  It’s not all bad news though!  Some home owners have thought that it means they need to buy new gutters.  That is not the case!  The vast majority of eaves in Durham are made from painted aluminum, and can be restored with a new coat of paint.

Your house wash is a necessary step before having your eaves repainted, and since the painters can now skip this step, you should see savings on your painting quote.

As with all our pressure washing services, your entire house including all siding, soffits, frames, eaves and any painted surfaces, is cleaned and sanitized.  This means that all mildew, algae, mold and dirt is completely removed, and the surface is paint ready.

But, what if your eaves are very new?  Or perhaps only a few years old?  If you are seeing any kind of staining before the paint has oxidized, and it is not removed during a house wash, then there is another issue that needs investigating.  Do you have gutter guards or another similar product?  Gutter guards can cause run off that speeds up staining on the exterior of your eaves.  Any product that causes roof water to flow OVER the gutters, instead of inside, can cause premature staining.  We do not recommend any product that needs installation on top of eaves or gutters.  Yearly cleaning is more cost effective, and ensures the proper functioning of your gutters and down pipes.

The Bottom Line

A house wash will clean and disinfect the entire exterior of your home.  Tiger Stripes may even be vastly improved!  However, there may be some issues that require professional painting for perfect results.  Having your house washed before hand ensures that your new paint lasts for many years to come.


Updated:  April 22, 2023