By Aaron Koszyk, Owner, Double A Power Washing · 10 min read
Something is living on your roof right now, and it has been eating it all summer.
Those broad black and grey streaks running down the north slope of your lake home are not weathering. They are not oxidation. They are a colony of cyanobacteria called Gloeocapsa magma, and by September, after a full Michiana summer of humidity, the growth is as visible and as deep as it gets all year.
Most homeowners see it and put it on the list. That is the costly mistake. The organism does not pause for winter. It goes dormant, picks right back up in April, and comes back a little further into the shingles each season. Getting a soft wash roof cleaning done in September, before the lake communities close up and before southwest Michigan hits its first hard freeze, is the decision that saves you money long before a roofer ever enters the picture.
Quick Answer: Black streaks on asphalt shingles are Gloeocapsa magma, a cyanobacteria that feeds on limestone filler and shortens roof life, and a low pressure soft wash with sodium hypochlorite kills it at the root before the freeze and thaw season begins around Christiana Lake and Sister Lakes.
Key Takeaways
- Black streaks on asphalt roofs are Gloeocapsa magma, a cyanobacteria that feeds on the limestone filler in shingles and causes premature granule loss.
- Pressure washing shingles voids most manufacturer warranties and blasts away granules. Soft washing at low pressure is the method ARMA recommends.
- Sodium hypochlorite mixed with a surfactant kills the organism at the biological level. Rinsing alone does not.
- Roof area, pitch, degree of growth, and access all affect the cost of a cleaning. A soft wash job is a fraction of the cost of replacing even a single square of shingles.
- September is the right window for lake community homes: the growth is visible, the weather cooperates, and cleaning before freeze and thaw cycles protects the shingle granules through winter.
In This Article
- What Those Black Streaks Actually Are
- Why Pressure Washing Is the Wrong Tool for a Roof
- What Determines the Cost of a Soft Wash Roof Cleaning
- The Cost Comparison That Makes Roof Cleaning an Easy Decision
- DIY vs. Hiring a Pro
- Why September Is the Right Window for Lake Community Homes
- Frequently Asked Questions
What Those Black Streaks Actually Are
Gloeocapsa magma is a cyanobacteria: a photosynthetic microorganism that forms colonies and builds a dark pigmented sheath around itself as protection from ultraviolet light. That sheath is what you see on your roof. It is not dirt. It is a biological structure.
The organism spreads through airborne spores. Once a colony establishes on a shingle surface, it feeds on the calcium carbonate filler that shingle manufacturers mix into the granule base. That limestone filler adds weight and durability. As the bacteria metabolize it, the granule layer weakens. Granules loosen and wash into the gutters. The asphalt layer underneath then faces more direct UV exposure than it was built to handle, and it ages faster than it should.
On north facing slopes around Sister Lakes and Diamond Lake, the problem is often worse. Those surfaces stay damp longer after rain and morning dew, which is exactly the environment Gloeocapsa magma thrives in. A roof with years of service left can have that timeline shortened measurably by a colony that goes untreated for a few seasons.
Moss and lichen compound things further. Moss holds moisture against the shingle surface, and its root style structures called rhizoids work under shingle edges and lift them. Lichen bonds chemically to the granule surface and is harder to remove than algae alone. All three respond to soft washing. None of them respond to rainfall.
Why Pressure Washing Is the Wrong Tool for a Roof
The instinct makes sense: the roof looks dirty, so you reach for the highest pressure tool available. But asphalt shingles are not concrete. The granules that protect the asphalt layer are adhered, not embedded solid, and direct high pressure spray dislodges them.
The Asphalt Roofing Manufacturers Association has published guidance stating that high pressure washing is not an appropriate cleaning method for asphalt shingles. Many shingle warranty documents go further and explicitly void coverage if the shingles are cleaned with high pressure equipment. A homeowner who pressure washes to save money may end up voiding the manufacturer warranty in the process.
Soft washing uses low pressure, comparable to a standard garden hose, combined with the right chemistry. The active agent is sodium hypochlorite, the same compound used to treat municipal water supplies. Mixed with a surfactant that helps it cling to sloped surfaces, it penetrates the colony and kills the organism at the cellular level. The dead material rinses away cleanly. The shingle surface is restored without mechanical damage.
Our residential rig runs a 24-volt Zeus soft wash system with mixing valves, which lets us dial in the right concentration for what we find on the roof. Light early season algae gets a different mix than a roof carrying multiple years of untreated algae and moss. That calibration matters: too weak and the treatment does not reach the full depth of the colony; too strong and runoff becomes a concern for surrounding landscaping. We soak plants and beds with clean water before we start and rinse again after, the same protocol we follow on every house wash we do.
Pro Tip: Check your north facing slopes first. North facing roof surfaces stay damp longer after rain and morning dew, which is where Gloeocapsa magma colonizes fastest on lake area homes in Michiana.
What Determines the Cost of a Soft Wash Roof Cleaning
Every roof quote we give is based on the actual conditions of that specific job. There is no single number that applies to every home, and anyone quoting you a flat price without seeing the job is guessing. Here is what actually moves the cost.
Square Footage
Roof square footage is the baseline. We measure the cleanable surface area, accounting for slopes, dormers, and separate roof sections. A cottage on Christiana Lake and a larger main residence on the same waterfront are simply different amounts of surface to treat.
Pitch
Steeper roofs take more time, require more careful positioning, and in some cases limit what equipment can reach safely. A low slope ranch and a steep Victorian gable are not the same job even at the same square footage.
Degree of Growth
A roof cleaned within the past few years and showing light algae staining is a straightforward job. One that has never been professionally cleaned, with multiple growth types present, means more dwell time, potentially a second application, and more thorough rinsing. Heavier growth drives both time on site and chemistry cost.
Access and Stories
A single story home with a walkable roofline is more straightforward than a two story lake house where the upper section requires extended reach. Height adds time and complexity to the setup.
Distance
We travel throughout southwest Michigan, including the lake communities in Cass County around Dowagiac, Cassopolis, and Eagle Lake. Distance from our Mishawaka base is factored into quotes for locations that require longer drive time.
The right way to get your number is to call for a free estimate. We can often quote based on photos and a quick conversation about the home’s size and the age of the staining. For lake homes we have not visited before, we sometimes schedule a look before committing to a price, because access angles, surrounding landscaping, and neighboring structures all change the job.
See the Difference
Ready for a free, no-pressure estimate?
Call or text one of our exterior cleaning specialists, or request your quote online anytime.
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The Cost Comparison That Makes Roof Cleaning an Easy Decision
Roofing contractors sell shingles by the square, a 10-by-10-foot section. Material and labor for even a single square of asphalt shingle replacement in southwest Michigan is not a small line item, and a full roof replacement on a lake home of any size is a significant capital expense.
Soft wash roof cleaning costs a fraction of what replacing damaged shingles runs. The math is simple. If cleaning extends the usable life of a roof by multiple seasons, the investment is recovered quickly. A roof allowed to degrade from untreated biological growth may reach the point of replacement years earlier than it would have if the problem had been caught in the first season it appeared.
We are not in the business of overstating the drama of a dirty roof. Some homeowners treat regularly and get the full rated life out of their shingles. Others let staining go for years and still see reasonable longevity. But a roof visibly black with Gloeocapsa magma, especially one with moss working at the edges, is past the point of early warning.
For lake home owners who carry the property as a lasting investment, the calculation is straightforward: professional soft wash cleaning now, or a portion of a roof replacement budget later. The cleaning wins on cost every time.
DIY vs. Hiring a Pro
| Factor | DIY / Rental | Double A Power Washing |
|---|---|---|
| Effect on shingles | Rental pressure washer at high PSI dislodges granules and can void your shingle warranty | Soft washing at low pressure preserves granules and meets ARMA cleaning guidelines |
| Treatment chemistry | Consumer cleaners often lack the sodium hypochlorite concentration to fully kill the organism | Calibrated sodium hypochlorite and surfactant mix kills Gloeocapsa magma at the cellular level |
| Plant and landscaping safety | Runoff risk is high without soaking the beds first and rinsing them after | We soak surrounding beds with clean water before we start and rinse again after the treatment |
| Results | Cleaning the surface only leaves the biological root structure intact, so regrowth comes back faster | Full biological kill means the treated surface stays clean far longer before new spores can establish |
| Warranty exposure | High pressure cleaning can void shingle manufacturer warranty coverage | Soft washing method is consistent with manufacturer guidance and does not affect warranty standing |
Pro Tip: If your gutters are full of granules after a rain, the shingle degradation is already underway. That is the time to act, not to wait for the next season.
Why September Is the Right Window for Lake Community Homes
September is a narrow and useful moment. The summer season is winding down. You are on the property, or making your final visits before closing up. The growth that accumulated through June, July, and August is at its most visible right now, which makes it easier to assess and easier to act on.
Getting a roof cleaned before the first hard freeze also matters for the chemistry. Sodium hypochlorite works best when surface temperatures are above freezing. Once the Michiana area moves into its October and November freeze and thaw pattern, scheduling becomes harder and treatment conditions become less predictable.
The freeze and thaw cycle itself is hard on a roof that already has biological growth. Moisture collecting under moss or in surfaces covered in lichen freezes, expands, and contracts. Over multiple cycles, that movement works at shingle edges and surfaces. A clean roof sheds water more efficiently and gives ice and snow less to grip.
Lake homes around Sister Lakes, Christiana Lake, and the communities near Dowagiac and Cassopolis also tend to sit unoccupied through the winter. A homeowner who addresses the roof in September before closing up comes back in the spring to a clean surface instead of another year of growth.
The organism killed by the treatment does not recover. New spore settlement can begin again over time, but the treated roof starts the following season in far better shape than an untreated one. We are in these communities regularly. If you are making your last few trips out before winter, this is the service worth putting on the schedule.
Looking for more than roof cleaning? We also offer house washing, concrete cleaning, roof cleaning, and gutter cleaning throughout the Dowagiac area.
Why Choose Double A Power Washing?
We have been cleaning roofs throughout the Michiana area since 2019. We are PWNA members, BBB A+ accredited, and fully licensed and insured. Our residential rig runs a dedicated soft wash system built for roof work, not a pressure washer dialed down as an afterthought. The concentration we mix, the dwell time we allow, and the rinsing protocol we follow are all specific to the surface and the degree of growth we find when we arrive.
We work in the southwest Michigan lake communities regularly, including the Cass County corridor from Edwardsburg through Cassopolis and out to Dowagiac. Lake homes often have landscaping tight to the house, propane setups that need to stay dry, and docks or outbuildings nearby. We account for all of that before we start the pump.
Our Google rating is 5 stars across 127 reviews from customers in communities like yours. We do not subcontract the work or send a crew you have never spoken to. When you call, you are talking to the people who show up.
What Our Customers Say
“Job well done. Even with bad weather was able to complete washing before party I was hosting. Appreciated job well done and upholding a commitment.”
— Mary Dockerty, Google Review
Frequently Asked Questions
Are black streaks on a roof actually damaging the shingles, or is it just cosmetic?
It is not just appearance. The streaks are Gloeocapsa magma, a cyanobacteria that feeds on the limestone filler in asphalt shingles. As the filler is consumed, the granule layer weakens and granules begin washing into the gutters. Once granules thin, the asphalt underneath takes more direct UV radiation than it was built to handle and ages faster. A heavily stained roof left untreated for several seasons loses real service life.
Why not just pressure wash the roof instead of soft washing?
High pressure washing physically removes granules along with the staining, and those granules do not come back. Many shingle manufacturers void their warranty if the shingles are cleaned with high pressure equipment. The Asphalt Roofing Manufacturers Association recommends low pressure soft washing as the correct method. We use a dedicated soft wash system that cleans with chemistry at low pressure, not with force, so the shingle surface stays intact.
How long does a roof stay clean after soft washing?
The sodium hypochlorite treatment kills the existing organism. New airborne spores can settle and begin colonizing again over time, but a treated roof typically stays visibly clean for two to four years depending on the roof’s exposure, the tree canopy overhead, and how much moisture the surface retains. North facing slopes and heavily shaded roofs tend to see new growth return sooner than south facing open surfaces.
Is the soft wash treatment safe for gutters and downspouts?
Yes. The chemistry we use for roof work rinses cleanly through aluminum, vinyl, and painted steel gutters and downspouts without causing damage. We flush gutters with clean water as part of the rinse process. If your gutters need a cleanout while we are there, that is a service we can bundle with the roof cleaning.
How do I get a quote for roof cleaning near Dowagiac or Cassopolis?
Call us at (574) 221-8400 or visit doubleapowerwashing.com to request a free estimate. For most lake homes we can quote based on a conversation about the home’s size, the age of the staining, and any photos you can share. For properties we have not visited before in the Cass County area, we may schedule a quick look before finalizing the number. Either way, there is no cost to get a quote and no obligation.
Before you close up the lake home for the season, take one look at the north slope of the roof. If you see black or grey streaking, that is not something to carry through another Michigan winter. The freeze and thaw season will not let it rest, and next spring it will be a season further along.
We serve the southwest Michigan lake communities including Sister Lakes, Christiana Lake, Diamond Lake, Eagle Lake, and the Dowagiac and Cassopolis areas, along with our home base in Mishawaka and the broader Michiana region. A soft wash roof cleaning scheduled now gets done before the weather closes the window and before you are managing the problem from three states away.
Call us at (574) 221-8400 or get a free estimate at doubleapowerwashing.com. We pick up the phone and we show up on time.
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