What Am I Seeing On My Siding?


Seeing dirty stains and other residue on the siding of your home is common, especially without routine maintenance. Part of the reason staining is so common on siding is that there are several different types. In this article, we will help you identify the types of stains most commonly found on the side of your home and what tends to cause them.


Dirt is the most basic stain you will see on your home. There are many ways that dirt attaches itself to your siding, some of which are caused by the elements. For example, if there is a bad storm with a lot of wind, loose dirt and mud can be blown through the air and end up on your home. Wind, storms, cars driving by your house or even mowing your lawn can cause particles to fly into the air and leave your siding a mess. No matter what form of siding you have, dirt will inevitably collect on its surface.


Algae generally appears on the north side of your home. One reason for this is that the north side of your home gets less sunlight than the other sides. Algae and mold form more easily in darker conditions and moisture. If untreated, additional dirt can make its way to your siding that algae can feed on, causing it to widen its coverage.

Mold and Mildew 

Excessive moisture is the main cause for mold and mildew growth on your home. Moisture somewhere on or beneath the surface can cause this to happen. It could be that rainwater got trapped behind the siding or even within the material. It’s also possible that there’s a broken drain pipe or gutter constantly dripping water on the siding, causing it to stay wet. That’s basically an invitation for mold or mildew to start growing on a house.

How to Help

Professionally washing your siding on an annual basis is the best way to keep it protected from dirt and mildew growth. Leaving these contaminants on your home can cause the stains to embed themselves, and the algae will make its way back over time after an initial wash. By having the house washed annually, you will be able to keep your largest investment looking great and protected from algae growth.


Stain removal and preventative maintenance are synonymous with K&T Windows. Our team of professionals has been helping homeowners keep their properties clean for years. Whether it is algae, mold, mildew, or any general surface contaminant, our soft wash process coupled with specialized cleansers is designed specifically to kill these on-site. If you would like to learn more, read all about our house wash, roof treatment, and our other power washing services.