How to Clean Algae or Mold Off Your Roof Shingles

Living in a humid area of the country like Florida, you’ve probably seen your asphalt shingle roofs with unsightly dark streaks on them. A blue-green algae known as Gloeocapsa Magma could be the reason you have the algae which is spread by airborne spores. Sometimes it can also be caused by an accumulation of mildew, mold, dirt, or defective shingles.

This discoloring can hurt the beauty of your home’s curb appeal and the resale value of your home if you have it up for sale.

Algae stains don’t show up below the metal flashing around chimneys or roof vents because the copper and the zinc coating on galvanized sheet metal are toxic to algae. Whenever it rains, trace amounts of metals are washed down the roof, inhibiting algae growth.

Algae Resistant Shingles

“In recent years, roofing manufacturers have begun mixing copper granules into roofing products to produce algae resistant shingles. If you live in an area susceptible to algae growth, be sure to specify this type of shingle when replacing your roof,” reports Today’s Homeowner.

Chemical Cleaning

Today’s Homeowner states that “algae stains can be removed by cleaning, though they usually return. While an occasional cleaning might not harm your roof, repeated use of harsh chemicals, or the erosive effects of pressure washing, can damage or shorten the life of asphalt shingles. There are several products on the market specifically designed to remove algae stains from roofs, such as Wet & Forget Outdoor. A mixture of trisodium phosphate (TSP), bleach, and water will also remove stains. Oxygen bleach lightens stains as well and is less harmful to the environment, but it doesn’t produce as immediate or dramatic an effect as chlorine bleach”.

Cleaning

Here are instructions on how to clean mold off roof shingles by DoItYourself.com:

Step 1 – Protect Your Plants and Lawn

Splash the plants and parts of your lawn that are close to the sides of your house with water to protect them from the bleach solution. You can also cover them with tarps or plastic sheeting, which will protect the soil around your plants as well. Make sure that you create a wide radius around your home to be safe.

Step 2 – Make and Apply the Bleach Solution

Put on rubber gloves and a breathing mask before proceeding you so you can protect your skin and your lungs from the fumes produced by both bleach and trisodium phosphate. In a two-gallon bucket, create a cleanser composed of 1/4 chlorine bleach and 3/4 water. Then, add one tablespoon of trisodium phosphate (TSP) and mix well. Fill a handheld pump sprayer with the solution, and apply it to the moldy shingles only.

Step 3 – Check for Cleanliness and Rinse

Allow the solution to soak into the shingles for at least 15 minutes. If they are severely molded, you may want to give it a little longer. Next, rinse the shingles thoroughly with a garden hose at low pressure. Start from the top shingle and rinse downward to prevent water seepage.

Run your gloved hand over the shingles to check for any slimy mold remaining after you’re finished rinsing. If some remains, apply the cleanser again, wait 10 more minutes, and repeat the rinse process.

Step 4 – Take Precautions

Never use a pressure washer to wash or rinse shingles. The concentrated jet will scrape off the small pebbles on top of the shingles and reduce their water repellency, which will only make your mold situation worse.

If you have a consistent problem with mold growth on your roof, consult a roofing professional. Your shingles may be old and in need of replacement, or just in need of waterproof coating to help prevent them from getting too wet.

No. 1 Home Roofing is proud to be a GAF Certified Roofing Contractor and an Owens Corning Preferred Contractor.

No. 1 Home Roofing is a family owned and operated roofing company conveniently located on US Highway 19 in Palm Harbor, Florida. We are dedicated to providing top quality workmanship and materials to ensure that your new roof is done right. We specialize in shingle, tile, and flat roof installation, repairs, and maintenance. Contact us for an appointment and/or estimate at 727-781-7663.

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