Black Stain On Roof? 5 Solutions for Removing It

August 4, 2023

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black stain on roof

Finding unsightly black stains on your roof can be frustrating. Not only are they ugly, but they can also indicate deeper issues with your roof's health. 

How can you remove black stain on roof? Try household cleaners like diluted bleach or TSP to lift minor stains from shingles. For widespread staining, use a pressure washer on low settings while pretreating heavily stained areas. Specialized algaecides and roof cleaners work well on tougher mold, mildew, and algae stains. As a last resort for stubborn stains, repaint affected areas or hire a professional roof cleaning service.

The good news is that there are solutions for removing black stains from roofs. Here are 5 effective methods to try.

What Causes Black Stain On Roof?

Before looking at solutions, it helps to understand what causes black stains in the first place. There are a few common culprits:

Algae and Moss Growth

In damp, shady areas of the roof, algae and moss can grow. As these organisms proliferate, they leave behind black stains. Areas with poor ventilation and airflow are especially prone to algae and moss growth.

Mold and Mildew

Like algae and moss, mold, and mildew can leave black stains. Mold grows in moist areas lacking sunlight. High humidity levels can also cause mold growth.

Asphalt Degradation

On asphalt roofing shingles, the asphalt coating can degrade over time. This causes black streaking down the roof. Prolonged sun exposure, harsh weather, and normal wear and tear can all degrade asphalt.

Pollutants and Dirt

Environmental pollutants like soot, dirt, and pollen may accumulate on the roof. This can lead to black staining, especially if the roof isn’t cleaned regularly.

Chemicals from Cleaning Products

Harsh chemical roof cleaners can actually cause black stains. Copper-based algaecides, in particular, can react with the roofing material and leave behind black deposits.

Now that we know what causes black roof stains let’s look at solutions for removing them.

1. Use Household Cleaners

For minor black stains, household cleaners may do the trick. Try using a dilute bleach solution or trisodium phosphate (TSP) cleaner. Use a soft scrub brush to gently apply the cleaner to stained areas. Let it sit for 10-15 minutes before rinsing thoroughly.

Bleach can lighten or remove some types of black stains. TSP is good for breaking down and removing dirt, mold, mildew, and other organic stains. Be cautious using these chemicals on metal or other delicate roofing.

roof cleaning products

2. Pressure Wash

Pressure washing packs more cleaning punch than household cleaners. This is a good option for larger roofs with widespread staining. Make sure to use the proper pressure setting - start on the low end first. High pressure could damage shingles or roofing materials.

When pressure washing, work methodically across the roof. Pre-treat badly stained areas with a roof cleaner before power washing. For best results, lightly scrub with a soft brush while pressure washing.

3. Use Algaecides and Roof Cleaners

Specialized roof cleaning chemicals can tackle tough black stains. Look for algaecide cleaners formulated to kill and remove algae or moss growth. These detergents help dissolve and wash away the grimy buildup caused by algae.

You can also find heavy-duty roof cleaners for dissolving mold, mildew, dirt, and other stains. Use caution with these harsher chemicals, and don’t mix cleaners together. Thoroughly rinse the roof after cleaning.

4. Repaint Stained Areas

For stubborn black stains that resist cleaning methods, repainting affected areas can provide a fresh look. Use exterior primer and paint formulated for roofing. The new coat of paint masks existing stains.

This works best for smaller stained patches rather than large areas. Completely repainting an entire roof is costly. Covering only the most noticeable black stains with paint is a more affordable solution.

5. Hire a Professional Roof Cleaning Service

For extensive black stains, the safest and most effective solution is hiring professional roof cleaners. They have industrial equipment and chemicals not available to homeowners. Professionals also have experience addressing all types of roof stains.

Be sure to hire reputable cleaners who won’t damage the roof in the process. Talk to them about eco-friendly options to avoid harmful chemicals. Professional cleanings can be expensive but provide the best stain removal results.

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Don’t let black stains ruin the look of your home’s roof. With the right cleaning methods, you can safely remove them. For minor stains, try household cleaners and scrubbing. Pressure washing also helps lift more difficult stains. Roof cleaners and algaecides tackle severe staining from mold or algae growth. Repainting stained spots or hiring a professional are other options for dramatic results.

With some time and elbow grease, you can restore your roof’s appearance and get rid of unsightly black stains. The solutions above will help you find the most effective cleaning method.

About Tampa Bay Roof Cleaning

At Tampa Bay Roof Cleaning, our customers are always treated right! We use top-notch tools, equipment, and eco-friendly soaps that make roofs, siding, windows, and more look their best. Please feel free to call our fully licensed and insured business now for a zero-cost quote. We can be reached at (813) 295-7443.


What are the stains on roofs?

The most common causes of black stains on roofs are algae, moss, mold, and mildew growth in damp areas that lack sunlight. Other sources of unsightly black stains are degradation of the asphalt shingle coating over time, the accumulation of environmental pollutants like dirt and soot, and even chemicals from harsh roof cleaning products. Areas on the roof that don't get much sun or have poor ventilation are prone to mold, algae, and moss growth that leaves behind telltale black stains. On asphalt shingle roofs, the black streaking could be a sign that the asphalt coating is starting to break down from prolonged exposure to sun, weather, and age. Environmental factors like soot, pollen, and dirt settling on the roof can also lead to black-stained areas if the roof surface isn't cleaned regularly.

What does roof fungus look like?

Roof fungus, such as algae, moss, mold, and mildew growth, can cause black stains on shingles and roofing materials. In the early stages, roof algae may just look like dark patched areas or black spots concentrated in one area of the roof. As algae spread, it forms a continuous black film or streaking across the roof surface. Moss growth starts out as a powdery black or green coating before forming dense clumps and matted areas. Mold and mildew form black or brown blotchy patches that spread in size. Advanced fungal growth causes thick black deposits and staining across large sections of the roof. Checking your roof regularly makes it easier to identify fungus in its early stages before severe staining occurs.

What does roof discoloration mean?

Roof discoloration refers to a change from the roof's original color, often indicating damage or wear. Dark streaks or splotchy areas are common discolorations on older asphalt shingle roofs, signaling deterioration of the asphalt coating. Black or brown stains point to fungal growth like algae or moss, which thrive in damp areas of the roof. Rust stains occur when water causes metal roofing, gutters, or other flashing to corrode over time. White spots or patches suggest mineral deposits from hard water runoff accumulating on the roof. Discoloration from environmental factors like soot and pollution accumulate more readily on roofs in need of cleaning. Severe or widespread roof discoloration usually means the roof surface has suffered considerable wear and damage.

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