How to Remove Mold on a Roof

If you’ve ever driven around your neighborhood, you’ve probably spotted roofs that are streaked black with discoloration, stained, or even tinted green.  Mold, algae, moss, and mildew thrive atop roofs, especially on patches of roofs that are shaded from the harsh UV light of the sun.  So no, these are not signs that your roof is falling apart, just an indication that it’s the perfect environment to allow this type of growth to flourish.

Mold, mildew, moss, and whatever is growing on your roof is unsightly and possibly damaging.  Allowing this growth to remain can damage your shingles, and if your shingles can’t do their job, you could see a future of water damage and costly repairs.  Getting rid of this pesky problem doesn’t have to be an expensive, time-consuming chore.  It just takes a few household cleaners, some roof safety equipment, and access to water.

The Don’ts

You’ll be tempted to grab your power washer and buckets of bleach, especially if you’ve spent a few minutes reading Internet forums on the subject of roof-cleaning.  Don’t.  Even on its lowest setting, a power washer can do some serious damage to your shingles, which after all, you’re trying to protect from mold and other growth.

Chlorine bleach is corrosive, too, so if you employ its use, you’ll damage metal roof flashings, gutters, and your metal downspouts.  Its runoff will hurt your landscaping, damage your shrubs and plants, and although the bleach may kill the first layer of growth, it might not kill the underlying layer.

The Do’s

Instead, use sodium hydroxide, also known as lye.  It won’t destroy your vegetation and for this purpose, works just as well as household chlorine bleach.  However, you’ll still need to wear protective gear because lye is corrosive.

Removing mold and growth off of your roof will depend on the weather forecast.  Choose a day that’s cool or even better, overcast.  You’ll also want little to no wind so when you’re spraying your solution, it won’t be carried by a gust of wind.  Move any lawn furniture and still take a precaution of covering your landscaping—just in case.

How to Remove Mold & Growth Off of Your Roof

You’ll need a garden hose, nozzle attachment, your noncorrosive roof cleaner, your roof-climbing safety equipment, and a supplemental water pump to clean your roof.  Instead of a garden hose, you can use a special rinsing tool that is designed to dislodge mold, algae, and growth from roof shingles.  It’s pricier, but it’s recommended if your roof frequently experiences issues with growth or if your home has low water pressure.

Overall, here’s how you’ll clean your roof free of mold and crud: you’ll start by saturating a vast area of your roof’s shingles with your cleaner, beginning at the bottom row and working your way up to the peak.  You’ll spray until you begin to see runoff.  Then, you’ll repeat by spraying any areas that have noticeably begun to dry.

If using a special rinsing tool, move it in a back-and-forward motion as if you were vacuuming, which will properly kill off any growth between the shingles.  Mix your cleaner product with water in a 1:7 ratio, pouring it into your pump sprayer.  Next, climb to the roof and soak if off with water to prevent the cleaner from drying out too quickly.  Going slowly, spray the shingles with the mixture, wait for a half a minute, then rinse.

Remember, safety matters in this project.  It’s good to utilize a roof harness, and even better to have a friend or family member spot you from the ground.  Use gloves and an eye mask, heavy-treaded boots, and protective clothing, as you’ll be working with a corrosive cleaner.

When Prevention Counts

Perhaps your home is heavily shaded on the north- and west-facing areas, causing this growth to consume these portions of the roof and detract from the overall aesthetics of your home.  If it’s time to replace your roof anyway, consider installing shingles that are treated with algaecide, designed to prevent the growth of algae and other types of spores for the length of their warranty, which is typically about 10 years.

The only downside is that after the algaecide wears off of the treated shingles, the growth will be allowed to flourish and feed off of the moisture and limestone filler agents within the shingles.  An asphalt shingle roof can last anywhere from 15-20 years, so the growth would stay off for about half of its lifetime.

Considering that treated shingles will buy you 10 years, possibly longer, of not having to clean off your roof yourself or having to hire a professional roof cleaner to do the job, it’s quite possibly worth the extra cost—even if it doesn’t last forever.

Protect Your Roof by Caring for It

Cleaning your roof and setting free the mildew, mold, algae, and discoloration won’t just up your home’s curbside appeal, but protect your roof’s shingles.  You’ll have a happier, healthier roof and can avoid a future headache of potential damages.

At Feldco, we have a strong reputation for great quality asphalt shingles and colors that will complement your home. Thousands of homeowners choose Feldco over competitors. Speak to a product specialist and get a free quote online today.

Share this article:


Get started with

*View our privacy policy

Or call us at 1-866-4FELDCO®
or visit one of our locations.


window privacy options

Beginner’s Guide to Installing Window Blinds

The Complete Beginner’s Guide to Installing Window Blinds Embarking on ...
remodeling after kids leave for college

Empty Nest Makeover: Redecorating After Kids Leave for College

The Empty Nest Makeover: A Guide to Redecorating After Kids ...
installing roof vents

Step-by-step Guide: Installing A Plumbing Vent Through Your Roof

Step-by-Step Guide to Installing a Plumbing Vent Through Your Roof ...
young woman cleaning her front door

How to Clean Your Entry Door

How to Clean Your Entry Door: A Step-by-Step Guide for ...
Sliding Patio Doors

Why Patio Doors Drop and How to Fix Them

Why Your Patio Door Drops & How to Fix It ...

Book Today and Save!

Over 500,000 homeowners have trusted Feldco with their windows, siding and doors. Click the button below and we’ll get started on your quote!