Introduction

Roof stains are unattractive discolorations that can ruin a home's curb appeal. Luckily, they're often not too difficult to deal with.

I reached out to roofing and siding professional Niki O'Brien to learn what's behind these mysterious stains and what can be done about them.

"Roof stains can be caused by many different things," she told me. "In more humid climates, roof stains are often the result of some sort of organic growth — such as mold, moss, or even algae."

But while organic stains are a common cause of roof stains, they're far from the only culprit. "In Colorado, the stains we see on roofs are typically water stains, rust stains, stains from overhanging trees or bushes, or some sort of environmental factor," O'Brien says.

Here I've provided a step-by-step guide for dealing with one of the most common types of roof stains: moss or algae growing on asphalt shingles. If your home has a different type of stain, you may need to use a different kind of cleaner, but most of the steps will be the same.

Of course, if you don't have any interest in getting on top of your roof, it's best to call in a pro. But if your roof slope isn't too steep and you're comfortable working at heights, you can typically clean it yourself in a single afternoon.

Tools Required

Materials Required

• Nontoxic or noncorrosive roof cleaner