Soft washing is the only safe way to clean a Long Island roof. Using a pressure washer on your shingles can void your manufacturer warranty, strip protective granules, and cut 5–10 years off your roof’s lifespan often creating a repair bill far larger than the cleaning job itself. Here is exactly what you need to know before you let anyone near your roof with a wand.
Every week we get calls from Long Island homeowners who had someone pressure wash their roof and now they’re dealing with missing granules, lifted shingles, or worse, a leak. The frustrating part? The damage is completely avoidable. It happens because homeowners don’t know the difference between pressure washing and soft washing, and some contractors either don’t know or don’t care.
We’re Long Island Power Wash, based in Rockville Centre. We’ve cleaned hundreds of roofs across Nassau and Suffolk County, and this guide is going to give you the straight answer on what soft washing is, why it works better than pressure washing, and what it costs on Long Island.
What is roof soft washing?
Soft washing uses low-pressure water typically under 100 PSI combined with a professional-grade biodegradable cleaning solution to kill the algae, mold, lichen, and mildew that cause those black streaks and green patches on your roof.
Pressure washing uses 1,500–3,000 PSI or more. That level of force is fine for your driveway or concrete. It is not fine for asphalt shingles, which are designed to shed water, not withstand a high-velocity blast aimed directly at them.
The cleaning solution used in soft washing does the heavy lifting. It penetrates the algae and mold at the root level and kills it. The low-pressure rinse removes it without disturbing the shingle surface or the granules bonded into it.
Pressure washing vs soft washing: the honest comparison
| Factor | Pressure washing | Soft washing |
|---|---|---|
| Water pressure used | 1,500–3,000+ PSI | Under 100 PSI |
| Safe for asphalt shingles | No — strips granules | Yes — manufacturer approved |
| Kills algae at the root | No — blasts it off temporarily | Yes — chemical solution kills it |
| Results last | 6–12 months | 2–4 years typically |
| Risk of voiding warranty | High — most manufacturers prohibit it | None — ARMA recommended method |
| Risk of water intrusion | High — can force water under shingles | Very low |
| Roof lifespan impact | Shortens by 5–10 years | Extends lifespan by removing damaging growth |
Why those black streaks on your roof are damaging it right now
The black streaks you see on Long Island roofs are almost always caused by a bacteria called Gloeocapsa Magma. It feeds on the limestone filler in your asphalt shingles. Left untreated, it eats away at the shingle material itself shortening the life of your roof by years.
The green patches are algae or lichen. Lichen is particularly stubborn because it actually roots into the shingle surface. The longer it sits, the deeper it embeds and the harder it is to remove without damaging anything underneath.
This is exactly why soft washing works and pressure washing doesn’t. You need to kill the organism, not just blast it off the surface. Pressure washing removes the visible growth but leaves the roots and spores behind. Within 6–12 months the same streaks are back. With soft washing, the cleaning solution kills everything at the source and the results last 2–4 years on a typical Long Island roof.
Will soft washing damage my roof or gutters?
No. A professional soft wash uses biodegradable, low-concentration solutions and rinsed thoroughly with very low pressure. Your shingles, gutters, flashing, and landscaping are all safe when the job is done correctly.
The cleaning solution we use is specifically formulated for roofing. We also pre-wet and post-rinse surrounding landscaping before and after every roof job so your shrubs and lawn aren’t affected.
What does damage roofs is high-pressure washing, incorrect chemical concentrations, or someone who mixes up their equipment and walks the roof with a standard pressure washer. Always ask your contractor what PSI they use on roofs. If they don’t immediately say “under 100 PSI” that’s a red flag.
How much does roof soft washing cost on Long Island?
For most Long Island homes, roof soft washing runs between $300 and $600. Here’s a realistic breakdown:
| Home size | Roof area (approx.) | Estimated cost |
|---|---|---|
| Small ranch (under 1,200 sq ft) | ~1,400 sq ft roof | $275 – $350 |
| Mid-size colonial (1,500–2,200 sq ft) | ~1,800–2,600 sq ft roof | $350 – $500 |
| Larger home (2,500+ sq ft) | 3,000+ sq ft roof | $500 – $700+ |
| Heavy lichen or long-neglected roof | Any size | Add $75 – $150 for treatment |
Steep pitch, two-story access, or multiple valleys will add to the cost. We give honest estimates over the phone or from a quick look in person no surprises on the day of the job.
Also worth noting: if you’re already having us out for a house soft wash or a house pressure wash, bundling the roof at the same time almost always saves you money on the total visit.
How often should you soft wash your roof on Long Island?
Every 2–3 years is the general rule for Long Island. Our climate humidity off the Sound, heavy tree cover in a lot of neighborhoods, and warm summers creates ideal conditions for algae and moss growth. If your home is heavily shaded or surrounded by trees, you may need cleaning closer to every 2 years.
A good sign you’re overdue: visible black streaks, green patches near the edges, or dark discoloration around the north-facing sections of the roof (the side that stays shaded and damp the longest).
We serve Nassau and Suffolk County
We clean roofs throughout Long Island. Whether you’re in Garden City, Rockville Centre, Great Neck, Syosset, or out in Suffolk in Huntington, Smithtown, or Bay Shore we’re local, we’re licensed, and we know exactly what Long Island roofs deal with season to season.
We also handle roof soft washing as a standalone service or as part of a full exterior clean that includes your siding, deck, fence, and driveway. One visit, one price, and everything looks clean at the same time.
Ready to schedule your roof soft wash?
We’re Long Island Power Wash based at 24 Lawrence Ave, Rockville Centre, NY. Give us a call and we’ll give you a straight quote, no runaround.
📞 +1 516-894-2994
Serving Nassau County and Suffolk County including Garden City, Hicksville, Huntington, Smithtown, and all surrounding communities.
