Roof Cleaning & Soft Wash

Gloeocapsa magma is a cyanobacterium (blue-green algae) carried airborne and deposited on roofs across the eastern US. It thrives on north-facing slopes that stay shaded and damp, where it feeds on the limestone filler used in asphalt shingle manufacturing. The visible black streaks are the dead cells layered on top of the actively growing colonies underneath.

Why north faces? Sun exposure dries the south face fast enough to suppress growth; north-facing slopes hold moisture for 4–8 hours longer per day, especially in fall and spring. In Bergen, Passaic, Essex, and Hudson counties — all humid, all with dense tree canopy — north faces are where 90% of gloeocapsa colonies establish.

What happens to the shingles. As gloeocapsa consumes the limestone filler, the asphalt matrix becomes more brittle and the granule bond weakens. Granules shed faster, the asphalt is more UV-exposed, and the shingles age 30–40% faster than designed. A roof that should last 30 years lasts 18–22. Worse, the failure mode is uneven (worse on north faces), so you can't predict failure by visual inspection alone.

Why moss and lichen are worse. Moss roots into the shingle granule layer and physically lifts shingles, exposing the asphalt and accelerating UV damage. Lichen is a moss-fungus symbiosis that's even harder to remove and produces acidic byproducts that accelerate granule loss. Moss and lichen require soft wash + manual removal, not just chemical treatment.

What the manufacturers say. GAF, CertainTeed, Owens Corning, Atlas, and IKO all publish maintenance bulletins specifically calling out gloeocapsa as a manufacturer-warranty issue. Failure to clean staining is not a covered warranty defect — but pressure-washing damage from improper cleaning IS a warranty-voiding installation defect. The ARMA Technical Bulletin (2020 revision) sets the soft-wash protocol that preserves warranty coverage.

Soft wash = under 100 psi. We use specialized 12V soft-wash pumps with adjustable spray heads designed for asphalt shingle cleaning. The pressure is comparable to a standard garden hose at full pressure, not a pressure washer. Solution does the work, not force.

Solution chemistry. Sodium hypochlorite (the active ingredient in household bleach, diluted to 1–4% depending on stain severity) + a biodegradable surfactant that suspends the dead algae for rinsing. We never use TSP, sodium hydroxide, or chlorine bleach in concentrated form — these damage shingles. We also never use products containing zinc copper sulfate as a wash agent (it's appropriate as a preventive strip but is corrosive when applied as a solution).

Pressure wash voids warranties. Pressure washing at 1,500–3,000 psi physically removes the ceramic granule layer on shingles. Granule loss is irreversible, exposes the asphalt to UV, and accelerates the same degradation gloeocapsa was causing — except faster and more uniformly. GAF, CertainTeed, and the other major manufacturers explicitly void warranty coverage when pressure washing has been performed.

Plant and landscape protection. The sodium hypochlorite solution will damage plants and grass if it lands on them. Before any application we pre-wet adjacent plants with clean water (which prevents absorption of the cleaning solution), cover sensitive landscaping with plastic, and rinse with copious clean water after the cleaning is complete. The neutralized rinse-off is safe for soil and storm drains.

Safety. Soft wash work uses harness + lifeline on any roof over 4/12 pitch per OSHA Subpart M fall-protection requirements. We don't subcontract roof cleaning to powerwash companies; our crews are full-time roofers who treat the roof with respect because they're going to be the ones repairing it if something goes wrong.

Why install strips. After a soft-wash cleaning, gloeocapsa will start to recolonize the roof within 18–36 months unless something prevents it. The most effective long-term preventive is a zinc or copper strip installed at the ridge — rainwater washes over the strip, picks up trace metal ions, and inhibits algae growth across the entire face below it.

Zinc vs copper. Zinc strips are the most common (lower cost, proven effective). Copper strips are premium (higher cost, slightly more effective, develop a natural patina). Both work; zinc is the right value choice for most NJ homes.

Strip spacing. One strip at the main ridge covers roughly 8–10 feet of slope below. Larger or more complex roofs need a second strip at hip ridges or mid-slope. We size and place based on slope geometry, not a template.

Service life. Zinc strips last 15–20 years; copper strips last 30+ years. Both are typically installed at the time of cleaning so the homeowner gets one labor mobilization for cleaning + prevention. Adds $250–$650 to a typical residential cleaning depending on roof complexity.

Do shingles with built-in algae resistance need strips? Modern algae-resistant shingles (GAF Timberline HDZ AR, CertainTeed Landmark AR, etc.) have copper granules embedded in the shingle face that provide built-in resistance. These are increasingly the default since 2015. If your roof is post-2015 and AR-rated, strips may be redundant. If your roof predates 2015 or you're unsure of the shingle spec, zinc strips are cheap insurance.

Past 80% of useful shingle life. If your roof is past 20–22 years old (asphalt) and has visible granule loss, exposed mat fiber, or curling at the eaves, cleaning is throwing money at a roof that needs replacement. We'll inspect first, give you the honest assessment, and quote replacement instead of cleaning if that's the right call.

Active leaks. Cleaning a roof with active leaks just gets water inside the building faster. The leaks need fixing before any cleaning happens — usually flashing rework, valley repair, or shingle replacement.

Heavy moss with deck damage. Moss that's been growing for years can root into the shingle granule layer and damage the underlayment below. If our inspection shows deck or underlayment damage, cleaning won't restore the roof; partial or full replacement is the right scope.

Roofs under home sale. If you're selling within 12 months and the buyer's inspector is likely to flag the staining, cleaning is worthwhile. If the home isn't selling soon and the shingles have plenty of life left, cleaning is a maintenance investment — typical payback is 5–10 years of extended shingle life for a $400–$900 cleaning cost.