It can be difficult to stay on top of all the problems that can afflict a home — especially mold. While mold is an issue anywhere in your home, it can be especially frustrating when it appears in out-of-the-way places, such as your home’s roof, as you may not spot it right away. But just because it’s out of the way doesn’t mean it’s not a risk to your home.

This guide will help you detect mold on your roof, explain how you can get it off, and show you how to prevent it from occurring.

The Dangers of Mold on Your Roofing Shingles

First of all, if you detect what you think may be mold in your house or on your roof, make sure it’s mold and not mildew, which is benign and not a cause for alarm.

Mold on Your Roofing Shingle
Image Credit: Canva

Mold forms when moisture dwells on your roof’s surface. The process usually begins with the formation of small spots that transform into streaks on your roof’s surface. From there, it can spread quickly and aggressively. 

It leaves unsightly streaks on your roof and can make it slippery and cause rotting in the roof sheathing. Mold on the roof can even spread to the home’s interior. According to All Dry USA, mold takes only 48 to 72 hours to migrate from the roof to inside the house. So, having a quick response to roof mold is essential.


Steps to Clean Mold Off Roofing Shingles

Taking care of mold in its early stages is an easy process that likely won’t even require a trip to the hardware store. With a bucket, garden hose, bleach, and an old broom, you can take care of the problem before you need professional help.

Before starting, take necessary safety precautions: Wear rubber gloves, eye protection, a breathing mask or respirator, and cover any exposed skin. Also, cover surrounding vegetation with tarps or plastic sheets to prevent damage from cleaning solution runoff. 

As always, practice proper roof and ladder safety. Be careful when climbing onto your roof, and use a sturdy, secure ladder (make sure to lash it to your roof). If you have a high or steep roof, use a safety harness.

Once on the roof, gently scrub shingles with a stiff bristle brush to loosen stuck-on mold. Wear a mask to avoid inhaling dislodged mold particles.

Chlorine bleach effectively kills mold. Buy a premixed solution or make your own by mixing one quart bleach, one gallon water, and 1⁄4 cup trisodium phosphate in a large container (phosphate helps remove staining).

Use a pump sprayer for maximum coverage and ease of application. Avoid pressure washing, as forceful water can damage shingles.

Spray the entire roof, starting at the bottom row. Continue spraying until you see runoff, allowing 20 minutes of soak time. Set a timer to track soak duration.

Rinse thoroughly after 20 minutes. Use a garden hose or refill your sprayer with fresh water to rinse. Rinse from the top down until no bleach scent remains. If bleach sits on the shingles, it can discolor them, so be thorough in this step. 

Prevention Tips to Avoid Roof Mold

While periodic cleaning is important, preventing mold is an even better option. Here’s how:

  • Install zinc or copper metal stripping along roof seams and edges. Its antimicrobial properties deter mold.
  • Perform an annual washing to remove mold, moss, and mildew before extensive growth.
  • Quickly replace damaged or missing shingles to prevent moisture from getting under other shingles.
  • Clean clogged gutters and downspouts to quickly and thoroughly remove water from the roof.

Professional Mold Remediation

If mold growth covers a large area or frequently reappears, I don’t recommend DIY removal using home methods. Professional mold remediation is a better solution. Companies like All Dry USA use commercial-grade sanitizers, equipment, and techniques to remediate even the worst cases of mold growth.

Although most handy homeowners can manage to get rid of small mold spots, leave any extensive growth to the professionals. They can give you confidence that the growth is thoroughly removed and won’t return to threaten your home. 

So, Is Mold Removal Worth It?

Mold can threaten the integrity of the roof and home’s interior, so removing it is always worth it. For mild cases, it’s a manageable DIY project that shouldn’t take longer than an afternoon.

But for severe cases, I would hire a professional. Mold infestation can be insidious and hard to root out, and you definitely don’t want it to migrate from the roof to the interior. A professional can treat the mold and ensure it won’t return. 

Frequently Asked Questions

Can I use natural cleaners instead of bleach for mold?

Yes, hydrogen peroxide, vinegar, baking soda, ammonia, or tea tree oil make effective natural antimicrobial cleaners that can get rid of mold. However, bleach remains the strongest mold removal agent in most cases.

Why does mold keep recurring soon after I clean the roof?

Rapid mold recurrence likely signals an unaddressed moisture issue like flashing leaks, defective shingles, clogged gutters, or insufficient attic ventilation. Consult a roofing contractor or mold specialist for a consultation and inspection.

Is household mold exposure seriously hazardous?

The degree of risk to a person’s health caused by mold exposure is a question for medical professionals. However, as a general rule, mold can and does affect people’s respiratory health, so you should fix mold infestations as soon as possible.

Editorial Contributors
avatar for Doug Sluga

Doug Sluga

Doug Sluga is a professional roofer and carpenter with ten years of experience in residential and commercial construction. His expertise spans the breadth of the roofing trade from minor repairs to laying shingles to framing trusses. These days he spends most of his time writing about roofing and the roofing industry.

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photo of Lori Zaino

Lori Zaino

Lori Zaino is a freelance writer and editor based in Madrid, Spain. With nearly two decades of editorial experience, she’s written and edited for publications like Forbes, CNN, Insider, NBC, Newsweek, The Points Guy, The Infatuation, and many others. Having just completed her first home renovation, she’s more interested in home improvements than ever, dedicated to bringing you fresh and accurate content to help you update your living spaces.

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