Roof Streaks and Black Algae: What Causes Them and How Roof Cleaning Fixes It
If you have dark streaks on your shingles, you are not alone. Across Lexington, KY neighborhoods like Chevy Chase, Beaumont, Hamburg, and Masterson Station, those stains are usually a type of cyanobacteria commonly called black algae. It thrives on moisture, shade, and the limestone filler found in many asphalt shingles. The good news is that a gentle, professional approach to roof cleaning can remove the stains and help your roof look uniform again without harsh pressure.
At Pressure Washing Pros, we use methods designed for shingles, not sidewalks. That matters because improper cleaning can shorten roof life and void warranties. Never let anyone blast your shingles with high pressure; the right solution is a controlled soft wash that treats the growth and lifts it away.
What Those Black Roof Streaks Really Are
The “black stuff” is most often Gloeocapsa magma, a hardy organism that spreads its protective dark shell across shingles. The streaks appear where runoff carries the cells downward, making long, uneven lines. North- and east-facing roof slopes in Lexington tend to show stains first because they dry more slowly and get less midday sun.
Black algae does more than hurt curb appeal. The dark film soaks up heat, which can raise roof surface temperatures on hot Kentucky afternoons. Over time, colonies hold moisture and can trap debris, setting the stage for moss and lichen to take hold.
Why Lexington, KY Roofs Are Prone To Streaking
Our local weather is a big factor. Spring rains, humid summers, and long shade from mature trees around Tates Creek, Kenwick, and Gardenside create ideal conditions for growth. Pollen and leaf litter add a fine layer of organic material that algae uses like a starter meal. When nights are cool and mornings are damp, roofs stay wet longer, especially near valleys, chimneys, and under overhanging oaks and maples.
Homes with architectural asphalt shingles are most affected, but metal and tile roofs can show discoloration as well. Venting, insulation, and attic airflow also play a role because warm, moist attic air can raise the temperature of the sheathing and lengthen dry times at the shingle surface.
How Professional Roof Cleaning Fixes It
Effective treatment targets the organism, not just the stain. A soft wash uses measured application of cleaning solutions at low pressure, allowing dwell time to break down the protective coating on the algae. Rinsing is gentle so granules stay in place. The goal is a clean roof with intact shingle coating and no streaks.
On many Lexington homes, we schedule work for cooler parts of the day to protect landscaping and improve solution performance. Catch basins, downspouts, and nearby plantings are prepped and rinsed so everything around your home stays safe. Keeping people and pets off the work area is essential during and shortly after cleaning while surfaces are wet.
Algae, Moss, Or Lichen: What You’re Seeing On The Roof
Not all growth looks the same. Here is a simple way to tell what is likely on your shingles:
- Black algae: thin, dark streaks that follow the path of rainwater; surface feels smooth.
- Moss: green, fuzzy clumps that hold water like a sponge; often along shaded edges and north slopes.
- Lichen: flat, crusty, light green or gray patches that cling tightly to granules.
Each requires a gentle approach. Algae often clears quickly after treatment. Moss and lichen may take longer as their roots release. For long-term protection, treating early when streaks first show is the smartest move.
What Roof Streaks Can Do If You Ignore Them
Stains are more than cosmetic. When growth sits on shingles season after season, moisture lingers and granules can loosen. That can age the surface faster in high-sun areas like open lots in Andover or Masterson Station. As dark patches spread, roof temperatures can increase under summer sun, which does not help your cooling bills.
Unchecked streaks also make potential buyers think “roof replacement.” A clean, even roof color gives the right first impression if you plan to list your home near UK campus, Chevy Chase, or Beaumont by spring.
Why Soft Wash Beats High Pressure For Shingles
High pressure is for concrete, not shingles. The gritty coating on asphalt shingles protects the asphalt below. Pressure can strip that protective layer and force water up under tabs. A true soft wash uses low pressure and the right chemistry so granules stay put and the roof dries clean.
Professional teams manage water flow, protect landscaping, and control runoff. They adjust application based on roof pitch, material, age, and weather that day. Choose an insured, trained team that specializes in roof work, not just general washing.
Benefits Of Professional Roof Cleaning In Lexington, KY
- Restores curb appeal in one visit and brightens the whole property.
- Helps shingles dry faster after storms by removing growth that holds moisture.
- Discourages moss and lichen from taking root on shaded slopes.
- Supports roof longevity when paired with good attic ventilation and gutters that flow.
- Shows better in photos if you plan to sell in neighborhoods like Hamburg or Lansdowne.
If you want to see what this looks like on your home, read about our professional roof cleaning service and how we tailor the process to Lexington’s climate.
When To Clean: Timing For Central Kentucky Weather
Most homeowners in Fayette County plan cleaning from late spring through early fall, when temperatures are steady and daytime drying is reliable. That window gives enough warmth for solutions to work well and enough daylight to complete prep and cleanup. After heavy pollen in April and May, a mid-to-late season visit can clear grime and prevent a full season of streaking.
Winter can still be fine on mild days, but crews avoid freezing temperatures and high winds. In any season, early action matters. The first season of light streaks is simpler to treat than years of buildup layered with moss and lichen.
What To Expect On Cleaning Day
Here is a typical flow so you know what happens while our team is on site in Lexington:
We start with a walk-around to note landscaping, outlets, and downspout paths. Tarps and rinses protect shrubs and flowers common to yards in Chevy Chase and Kenwick. Gutters are checked for flow so rinse water moves off the roof freely. Technicians apply a measured soft wash to stained areas and let it work, then perform a careful rinse. Touch-up passes address stubborn patches. The site is wrapped up with a final rinse of nearby plants and hardscapes.
You do not need to be home, but access to water is required. Please close windows, move vehicles back from the driveway, and keep pets indoors until the work area is dry.
How Roof Cleaning Fits Into Your Home’s Exterior Care
Think of your roof as the umbrella for every exterior surface. When it is clean, rain flows as designed, and walls and sidewalks stay cleaner too. Pairing a roof treatment with gutter maintenance and occasional siding washing helps keep algae from hopping from surface to surface. If you ever need a quick overview of the full range of exterior care, you can start at our home base for roof cleaning in Lexington, KY and other services that support a well-kept property.
Common Myths About Black Roof Streaks
Myth: The roof is failing if streaks appear. Reality: Many roofs with black algae still have plenty of life left. A proper soft wash clears the discoloration so you can evaluate the surface without the film.
Myth: Rain will wash it away. Reality: Rain spreads the streaks by carrying cells downhill. Treatment is needed to neutralize the growth first.
Myth: Bleach alone will fix everything. Reality: Concentration, dwell time, and application method matter. The mix must be right for your roof material, and landscaping needs protection. That is why a trained crew is the safer choice.
Local Factors You Can’t Change, And What You Can Do
You cannot change the sun angle over Hamburg or the tall trees in Beaumont, and you would not want to. What you can do is act early when streaks show, keep gutters flowing, and schedule professional service before warm, humid stretches. A clean roof helps your home shed water, look cared-for, and feel cooler to the eye.
For many Lexington homeowners, a two- to three-year cadence works well, but the right timing varies with shade, slope, and roof age. We can assess your home and suggest a plan that fits your property and lifestyle.
Ready To See Your Shingles Again?
Streaks do not have to define your roof. If you want a safe, effective reset, our team at Pressure Washing Pros is here to help. Learn how our gentle roof cleaning process removes stains and respects your shingles, then schedule your visit by calling 606-231-4057. We serve homes throughout Lexington, KY and nearby communities.
Take photos of your roof before we arrive so you can compare the transformation from the same angles after cleaning. When you are ready, call or text us, and we will get you on the calendar.
