Pressure Washing Roof Shingles and Tile Guide for Tampa Bay

# Pressure Washing Roof Shingles and Tile Guide for Tampa Bay Black streaks and algae growth on Tampa Bay roofs are among the most visible indicators that a home is overdue for exterior maintenance. Florida's combination of humidity, warmth, and frequent rain creates ideal conditions for Gloeocapsa magma -- a cyanobacteria that produces the dark streaks common on asphalt shingles throughout Hillsborough and Manatee counties -- and for the algae and lichen growth that affects both shingle and tile roofs. Best Bay Services handles exterior cleaning and maintenance throughout Tampa Bay, including [Brandon](/handyman/brandon), [Valrico](/handyman/valrico), [Riverview](/handyman/riverview), [Plant City](/handyman/plant-city), and [Tampa](/handyman/tampa). ## Key Takeaways - High-pressure washing of asphalt shingles removes granules and voids manufacturer warranties -- low-pressure soft wash is the correct method for shingle roofs. - Concrete and clay tile roofs are more durable under pressure but still require technique discipline to avoid cracking tiles or forcing water under roof penetration flashing. - The cleaning agent does more work than the pressure on a roof cleaning -- sodium hypochlorite solution at proper dilution kills algae and removes biological growth at low pressure. - Black streaks on asphalt shingles are Gloeocapsa magma cyanobacteria, not mold, and are effectively removed by soft wash without any mechanical pressure. ## Why Tampa Bay Roofs Develop Algae and Organic Growth Tampa Bay's climate is ideal for the biological growth that discolors roofs: warm temperatures year-round, frequent summer rain that keeps roof surfaces moist, and high ambient humidity that promotes colonization of spores that land on roof surfaces from surrounding vegetation. **Gloeocapsa magma (black streaks on asphalt shingles):** The dark streaks commonly seen on Tampa Bay asphalt shingle roofs are caused by Gloeocapsa magma, a type of cyanobacteria that lives on the calcium carbonate in shingle granules. It is not mold and is not structurally harmful to the shingles at the same rate as lichen, but it darkens the roof surface in ways that affect curb appeal and can indicate a progression toward lichen if left untreated for several seasons. **Algae (green staining on tile and shingle):** Green algae grows rapidly on any roof surface that retains moisture. North-facing slopes and shaded sections under tree canopy develop algae faster because they stay moist longer after rain. Algae on concrete tile does not damage the tile itself but holds moisture on the surface, and the freeze-thaw cycle that affects porous tile in colder climates is not a factor in Tampa Bay -- algae on Florida concrete tile is primarily a cosmetic and early-stage biological concern. **Lichen (gray and green crusty patches):** Lichen is a symbiotic organism of algae and fungi that adheres more strongly to surfaces than algae alone. Lichen on asphalt shingles pulls granules from the surface when it is removed, which is why it is more damaging than algae or cyanobacteria. Lichen on concrete tile stains the surface and can cause spalling at the tile surface if left for many years without treatment in Florida's climate. ## Why High-Pressure Washing is Wrong for Asphalt Shingles Asphalt shingle manufacturers including Owens Corning, GAF, and CertainTeed explicitly warn against high-pressure washing in their warranty and maintenance documentation. The granules embedded in the asphalt surface layer are the shingles' UV protection -- they shield the underlying asphalt from direct sun and slow the degradation that eventually makes shingles brittle and prone to cracking. High-pressure water dislodges these granules from the asphalt surface, removing UV protection and shortening shingle service life. Warranty language from most shingle manufacturers voids coverage for damage caused by power washing above specified low-pressure thresholds -- typically 100 PSI at the nozzle for allowable cleaning methods. Standard residential pressure washers operate at 2,000 to 3,500 PSI, far above this threshold. Using standard pressure washing equipment on asphalt shingles is not a safe cleaning method for Tampa Bay shingle roofs. ## Soft Wash Method for Asphalt Shingle Roofs Soft washing uses a low-pressure pump and spray system to apply a cleaning solution, then rinses at low pressure or with rainfall. The cleaning agent does the biological work that high pressure does mechanically on other surfaces. **Cleaning solution:** A diluted sodium hypochlorite (bleach) solution at 1 to 3 percent concentration applied at low pressure is the standard soft wash solution for Gloeocapsa magma, algae, and mild lichen on asphalt shingles. Sodium hypochlorite kills the organisms at the biological level -- their root systems in the shingle granules -- rather than just washing away what is visible on the surface. A surfactant is added to the solution to increase dwell time and penetration into the organic growth. **Application:** Apply the solution at low pressure from a pump sprayer or soft wash pump, working from the ridge downward so the solution flows with the shingle direction. Allow adequate dwell time -- typically 15 to 30 minutes -- for the bleach to kill the organisms before rinsing. **Rinse:** A low-pressure rinse (garden hose pressure or a pressure washer at its minimum setting) removes the dead biological material and residual cleaning solution. Avoid high-pressure rinse nozzles even on the rinse pass. **Plant protection:** Sodium hypochlorite solution that runs off the roof and onto landscaping can damage or kill plants. Thoroughly pre-wet all landscaping under the roof drip line and rinse again after roof cleaning. For sensitive plantings, neutralizing agent can be applied after the rinse cycle. ## Concrete and Clay Tile Roof Cleaning Concrete and clay tile is more durable than asphalt shingle under pressure, but technique still matters for Tampa Bay tile roofs. **Working pressure for tile:** 500 to 1,200 PSI at a moderate distance with a wide fan nozzle (25 to 40 degree) is appropriate for most concrete tile surfaces. Higher pressure risks cracking aged concrete tiles, particularly on older Florida homes where concrete roof tile has been through twenty or more wet seasons and is more brittle than when installed. **Clay tile precautions:** Original clay tile, which appears on older Tampa Bay homes and some Mediterranean Revival constructions, is more fragile than modern concrete tile and should be treated with the soft wash approach rather than any mechanical pressure. Clay tile can crack under foot pressure as well as water pressure, and roof access for inspection and cleaning should be done carefully. **Flashing and penetration areas:** Keep pressure away from flashing at ridge caps, hip caps, and any penetration -- the areas most vulnerable to water intrusion. High pressure forced under an unseated flashing edge can push water into the roof system beneath the tile surface. **Lichen on tile:** Heavy lichen growth on Tampa Bay concrete tile may not respond fully to a single soft wash treatment. In cases where lichen is well-established, a follow-up soft wash treatment six to eight weeks after the first is more effective than increasing pressure -- the organisms die progressively after the bleach treatment, and a second application clears the residual staining. ## When Not to Clean a Roof Roof cleaning is not appropriate in several situations: - Shingles at the end of their service life: cleaning reveals the extent of granule loss and surface wear on old shingles, but the cleaned appearance is temporary if the roof is otherwise due for replacement - Active leaks: cleaning a leaking roof before repairing the source introduces more moisture to the system - Unstable tile: tile sections that rattle or have visible settlement should be assessed by a licensed roofing contractor before any cleaning work involves roof access - Within 72 hours of forecast rain: the cleaning solution requires adequate dwell time and rinse to be effective, and heavy rain within the treatment window washes away solution before it has completed the biological kill ## Related Services - [Pressure washing concrete and exterior surfaces guide for Tampa Bay](/blog/pressure-washing-concrete-guide-florida) - [Annual home checkup for Tampa Bay homes](/blog/annual-home-checkup-florida) - [Exterior caulking guide for Tampa Bay homes](/blog/exterior-caulking-guide-florida) - [Gutter cleaning guide for Tampa Bay homes](/blog/gutter-cleaning-guide-florida) ## Service Areas Best Bay Services handles exterior cleaning and pressure washing throughout Hillsborough, Manatee, and Pinellas counties, including [Tampa](/handyman/tampa), [Brandon](/handyman/brandon), [Riverview](/handyman/riverview), [Plant City](/handyman/plant-city), [Valrico](/handyman/valrico), [Thonotosassa](/handyman/thonotosassa), and [Bradenton](/handyman/bradenton). Call (813) 416-8676 or [contact us](/contact) to schedule an exterior cleaning assessment.