Got ugly algae, mold, mildew, or moss growing on your roof?

By Dan and Nick Cox:

Let’s face it… Dark stains running down your roofing shingles is just plain ugly!

So the next question you probably have is… What should you do about it?

Well, much of the time, it’s not really a problem, other than just cosmetic.

But in some cases, stains can be a symptom of something that can actually cause damage to your roof if left unchecked for too long.

The most common cause is, believe it or not, a type of algae that starts out as spores and turns into the dark stains. (Yea I know it looks like mold or mildew, but it’s not)

And it’s most common in areas of high temps and humidity, such as we have here in Maryland in the summer.

Another cause is moss or fungus, which feeds on the materials in the shingles and grows. This is usually found on the north side, or under shady areas. Left for an extended period of time, this can actually start to damage the shingles, leading to expensive roof repairs down the line.

Can algae and moss be safely removed?

The answer is yes… or no… well maybe…

Actually the best answer is “It depends”. There are several factors to consider such as how long it’s been there, how heavy a buildup of bad stuff there is, and how brave you are.

There are various liquid and chemical solutions to spray on the shingles, and kill the algae. For moss buildup, applying the right chemical and letting it naturally fall off often works the best. And NEVER use a brush!

Your best option is to get expert advice from a qualified, reputable Maryland roofing company (such as ourselves).

We’ll take a look, and let you know what the best plan is for your specific roof and situation.

It’s far too easy to cause more serious damage to your shingles if you approach it the wrong way. We’ve seen it far too often, and we don’t want it to happen to you.

Can you prevent new algae and moss from coming back?

There’s no 100% guaranteed way to prevent it, but…

Removing branches that block sunlight will help.

For a longer term solution, some people install copper or zinc strips under the cap shingles, leaving a couple of inches exposed at peaks, hips, and under the base of dormers. But the downside is it usually looks horrible, and most people don’t like it once it’s done..

These metals are toxic to algae, and after each rainfall, will drip metal molecules onto the shingles below, preventing algae and moss to grow.

(This is why you see fewer, if any, stains below chimneys, because of the flashing)

Get Algae Resistant Shingles

If your roof is older, or you need to replace your shingles anyway, then you’re in luck.

Many roofing shingle manufacturers now mix copper granules into their shingles to prevent algae growth. Remember though… They’re not a guaranteed solution, but will help prevent future stains.

However, they will not prevent moss from growing.

In summary…

Algae stains are definitely ugly looking, but usually don’t pose a problem or cause damages.

It may be possible to clean algae and moss, but not always.

Like everything, every home and roof condition is different.

If you have stains or something on your shingles that aren’t normal, the best thing to do is give us a call.

We’ll come out and give you a free assessment, and give you expert advice on the options you have.

If you have any questions, or want to schedule your
free, no-obligation inspection of your roof,
call Dan or Nick at 301-368-3551!

On Top Home Improvements, Inc.
10818 Avonlea Ridge Place
Damascus, MD 20872
Tel: 301-368-3551
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