Not every roof cleaning contractor is who they say they are. Here's how to verify licensing, insurance, and method before you let anyone on your roof.
A legitimate roof cleaning contractor carries general liability insurance, can hand you proof of it without a pause, uses a low-pressure soft-wash method instead of a pressure washer, and gives you a written estimate before anyone touches a ladder. If a contractor can't check all four of those boxes, keep calling around — the moss on your roof isn't going anywhere while you shop, and a bad contractor can leave you with more than stained shingles.
Nobody grows up dreaming of standing in a driveway squinting up at a roof trying to decide if that dark streak is moss, algae, or just a shadow having a bad day. And yet here we are. Moss doesn't care about your career goals, and neither does a Snohomish County roof that hasn't seen daylight since March.
What does a roof cleaning contractor actually do?
A roof cleaning contractor removes moss, algae, and lichen from a roof's surface, usually with a soft-wash treatment rather than high-pressure equipment that can lift shingle granules. The job typically includes a roof inspection, hand removal of heavy moss clumps, a moss-control treatment, and gutter clearing, since loosened debris runs straight downhill.
Does a roof cleaning contractor need to be licensed in Washington?
Washington's Department of Labor & Industries (L&I) registers contractors who work on homes, and a legitimate operator should produce a registration number on request. You can verify any contractor for free in about two minutes on L&I's own lookup tool before letting anyone near your roof — don't just take a business card's word for it.
What's the difference between soft washing and pressure washing a roof?
Soft washing uses low water pressure plus a moss- and algae-killing treatment to do the real work; pressure washing relies on raw water force alone. On an asphalt shingle roof, that difference decides whether you end up with a clean roof or a shorter-lived one.
- Soft washing — low water pressure plus a moss- and algae-killing treatment; the standard for asphalt shingle roofs because it clears growth without stripping the protective granule layer
- Pressure washing — high water pressure with little or no treatment; faster-looking results, but on shingles it can blast off granules, shorten the roof's life, and void some manufacturer warranties
- What to ask for — soft washing on shingles, and nothing that looks or sounds like a driveway pressure washer pointed at your roof
What insurance should a roof cleaning contractor carry?
At minimum: general liability insurance, and workers' compensation coverage if they show up with a crew. A certificate of insurance should name the actual insurance company, not just the contractor's own letterhead — and you're entitled to call that insurer directly to confirm the policy is active before work starts.
General liability insurance is the paperwork equivalent of a seatbelt: nobody wants to think about why they need it, everybody's glad it exists the one time a ladder meets a gutter meets somebody's parked car. We'd rather hand you a certificate you never have to use than explain after the fact why we didn't have one.
How much does a roof cleaning contractor charge?
Our own pricing for roof cleaning in Snohomish and North King County runs:
- Moss Removal + Powder — $450 per treatment, our standard moss clearing and zinc/moss-control powder application
- Full Roof Restoration — $649 per treatment, a deeper clean plus treatment for heavier moss and algae buildup
Nationally, cost guides commonly cite roof cleaning in the roughly $250–$650 range, with the number moving based on roof size, pitch, and how long the moss has had to get comfortable — that's general market context, not our rate, but it's a useful gut-check against a quote that seems suspiciously low.
What should be in a written estimate?
A real estimate names a price (or square footage breakdown), the cleaning method, what's included — moss removal, treatment, gutter clearing — and what counts as an extra, like a second-story surcharge. A contractor who won't put that in writing before showing up with equipment is telling you how organized the actual job will be.
What should you ask before you hire one?
These five questions separate a legitimate local contractor from someone with a truck, a pressure washer, and an app that lets them take payments.
- "Can I see your L&I registration number?" — a contractor who hesitates or can't produce one is telling you something
- "What method do you use — soft wash or pressure wash?" — high-pressure equipment can strip shingle granules and shorten your roof's life
- "Can I get that estimate in writing?" — scope, price, and timeline, before anyone sets foot on your roof
- "Do you carry your own insurance, or are you a sub for someone else?" — subs should carry their own coverage too, not ride on someone else's policy
- "Do you have recent local references or photos?" — a contractor who's done real work nearby should be happy to show it
What are the red flags of an unlicensed or uninsured contractor?
A legitimate contractor welcomes scrutiny — license checks, insurance calls, a written scope. These are the signs someone else wouldn't survive it.
- A bid that's dramatically lower than everyone else's, with no explanation for why
- Reluctance or outright refusal to share a license number or insurance certificate
- Pressure to pay the full amount up front, before any work has started
- No written estimate — just a verbal number and a handshake
- High-pressure power washing offered as the only option, with no mention of soft wash
How often should a roof actually get cleaned?
Most homes here do well with a professional cleaning every 1-3 years, depending on tree cover and how much shade the roof gets. A heavily shaded roof under fir or cedar trees — common from Lynnwood to Lake Stevens — moss-proofs itself faster than a south-facing roof in an open yard.
Western Washington doesn't really have a dry season so much as a slightly-less-wet season, and moss figured that out long before most of us moved here. It's not personal. It's just really, really good at its job.
Hiring locally
We've cleaned roofs for homeowners from Mukilteo to Kirkland, and the vetting questions above are the same ones we'd want a homeowner to ask us. If you want a second opinion on a quote you already have, or you're ready to book, you can see our full service area or get a free estimate in a couple of minutes.