Short answer: the streaks are Gloeocapsa magma, a cyanobacteria that digests the limestone filler in your shingles. It is removed with a low-pressure application at under 100 PSI, which is what every shingle manufacturer specifies. Typical Jacksonville cost is $375–$1,400.
You probably noticed it from the driveway, or from a neighbour's. Dark vertical streaks running down the north slope, heaviest below the ridge, spreading a little further every year.
It is not dirt, and it is not staining from the shingles themselves. It is a colony of cyanobacteria that arrived as airborne spores and settled in. What it eats is the powdered limestone that manufacturers use as filler in asphalt shingles — which means it is not sitting on your roof, it is consuming it.
That is the honest case for cleaning a roof, and it is a better one than curb appeal. Left alone, the colony holds moisture against the shingle surface, accelerates granule loss, and raises the roof temperature. Removed properly, a roof that looked ten years old can have most of its remaining service life restored.
Not sure what your property needs?
Send photos. We will tell you what we would do and roughly what it costs — even if the answer is that it can wait.
How roof soft washing works
The method is the same one every asphalt shingle manufacturer points to, and it has three parts.
A cleaning solution is applied across the roof at low pressure — closer to a garden sprayer than a washer. It kills the colony outright, usually within minutes. You will often see the darkest streaks fade while the crew is still on the roof.
The roof is then rinsed at low pressure and the surrounding landscaping is flushed. What we do not do is scrub, brush or blast to force an instant result, because all three of those remove granules along with the algae.
The rest happens without us. Dead organic material releases over the following weeks as rain works on it, which is why a roof photographed the day after cleaning usually looks good, and a roof photographed a month later looks better.
Shingle, tile and metal
Jacksonville has all three in quantity, and they are not interchangeable.
| Surface | Method we use | Pressure | Why |
|---|---|---|---|
| Architectural / 3-tab shingle | Soft wash | Under 100 PSI | Granule loss is permanent and accelerates UV damage. |
| Concrete tile | Soft wash, careful footing | Under 300 PSI | Tile is walkable but cracks underfoot if stepped wrong. |
| Clay barrel tile | Soft wash, minimal traffic | Under 200 PSI | Brittle, often original, and expensive to match. |
| Standing-seam metal | Rinse and treat | Under 500 PSI | The coating is the vulnerable part, not the metal. |
| Flat / low-slope membrane | Assessed first | Varies | Seams and terminations decide whether it can be cleaned at all. |
My roof is tile. Is it different?
The chemistry is similar; the risk is not. Tile roofs in Intracoastal West, Deerwood, Ponte Vedra and San Marco carry two hazards — cracking tiles by walking them wrong, and growth hidden in the valleys and under the leading edge that is invisible from the ground until it is severe.
Tile also costs more to clean, typically 25 to 45 percent above the shingle price, because it genuinely takes longer to do safely. Anyone quoting tile at shingle rates is planning to rush it.
Can you pressure wash a metal roof?
You can, and you should not. Metal itself shrugs off pressure, but the factory coating that stops it corroding does not. Abrasion from a narrow nozzle or a brush cuts microscopic channels in that finish, and salt air at the Beaches finds them quickly.
Metal roofs get a solution application and a low-pressure rinse. Panel seams and fastener washers get checked while we are up there, because those are where problems start.
What roof cleaning costs in Jacksonville
One thing worth knowing before you compare quotes: roof area is not house area. Once pitch and overhangs are counted, most roofs measure 15–25% larger than the home's footprint. A 2,000 sq ft house typically sits under a 2,400 sq ft roof.
Typical Jacksonville range
$375–$1,400
Roughly $0.25–$0.6 per sq ft of roof area
Roof area runs roughly 15–25% larger than your home's floor area once pitch and overhangs are counted. Tile costs more than shingle because it takes longer to walk safely.
| Job size | Typical range |
|---|---|
| Up to 1,500 sq ft roof — asphalt shingle | $375–$600 |
| 1,500–2,000 sq ft roof — asphalt shingle | $475–$800 |
| 2,000–2,500 sq ft roof — asphalt shingle | $600–$975 |
| 2,500–3,500 sq ft roof — asphalt shingle | $750–$1,250 |
| Concrete or clay tile roof | $650–$1,900 |
| Metal roof (rinse and treat only) | $400–$1,100 |
| What changes the price | Effect |
|---|---|
| Steep pitch (above 6:12) | +15% to 30% |
| Tile instead of shingle | +25% to 45% |
| Two-story with limited ladder access | +$100 to $200 |
| Pool or dense beds directly below | +$60 to $150 |
| Booked with a house wash | −$75 to $150 |
Ranges reflect typical Jacksonville-area jobs in 2026. They are planning estimates, not quotes — the real number depends on access, buildup severity, and what the surface is actually made of. See how Jacksonville pricing works across every service →
What to expect afterwards
Setting this expectation properly is the difference between a happy customer and a confused one.
- Day one: the heaviest streaking is visibly lighter. Some sections may look patchy — that is dead material still in place, not missed work.
- Weeks two to six: rain carries the residue off and the roof evens out. This is when most of the visual improvement lands.
- Months three onward: the roof holds. Regrowth normally takes two to four years in this climate.
If you are cleaning ahead of listing photos or an insurance inspection, book three to four weeks out rather than three days. Rushing it produces photographs of a roof mid-process.
Photo needed
Same roof photographed the day of cleaning and again four weeks later, from an identical angle — shows the gradual release that homeowners should expect
Plants, gutters and where the water goes
Everything applied to a roof ends up somewhere, and on most Jacksonville properties that somewhere is a foundation bed, a pool, or a lawn.
- Beds beneath every downspout and drip line are soaked before anything goes on the roof.
- Downspouts are redirected or temporarily blocked where the runoff would land somewhere sensitive.
- Pools and screen enclosures are covered or shielded, and the pool equipment gets checked before we start.
- Everything below the roofline is flushed once the roof is done, and again before we leave.
Roof cleaning also fills gutters with debris that has been sitting up there for years. If your gutters have not been cleared recently, doing both on the same visit makes sense — see gutter cleaning.
What roof cleaning will not do
- Repair anything. Flashing, underlayment, cracked tiles, corroded fasteners and ventilation are all roofing work, not cleaning work.
- Restore a worn-out roof. If the granule layer is already gone, cleaning reveals that rather than reversing it.
- Fix a leak. Sometimes it makes an existing leak more obvious, which is useful but not the same as fixing it.
- Guarantee it never comes back. Nothing does, in this climate. Zinc or copper strips at the ridge slow regrowth considerably and we will tell you whether yours are worth adding.
If the roof is near the end of its life, we will say so. Cleaning a roof that needs replacing is money spent twice.
Areas where roof algae is worst
Before & after
Roof algae streaks, before and after
Soft wash targets organic streaking on asphalt and tile without treating the roof like flatwork.
Algae streak soft wash before and after in Jacksonville
Answers
Roof cleaning questions
Do you pressure wash asphalt shingles?
Does roof cleaning void my shingle warranty?
What are the black streaks on my roof?
How long does roof cleaning take?
Will roof cleaning fix a leak?
Can you clean a metal roof?
Is it worth cleaning the roof before selling?
How often should a Jacksonville roof be cleaned?
Related
What people usually book alongside this
Upload roof photos for a soft-wash estimate
Street views plus a few closer shots of streaking, valleys, and nearby plants help us plan access and rinse paths.
Or email hello@jaxpropressurewash.com
What helps us quote fast
- One wide shot of each side that needs cleaning
- Close-ups of the worst staining
- Your address, so we can check the property size
- Roughly when it was last cleaned