Metal Roof Cleaning
in Seattle & the Eastside
Metal roofs are built to last 50 years — but algae, moss, and black streaking still take hold in the Pacific Northwest climate. Low-pressure soft wash removes the growth without touching the coating.
Why Metal Roofs Still Need Cleaning in the PNW
A metal roof does not absorb moisture and does not rot, but it is not immune to what grows on it. The Pacific Northwest climate — particularly the combination of coastal humidity, tree cover, and months of overcast — is excellent for algae, moss, and lichen regardless of what the roof is made of.
The black streaking that appears on many metal roofs here is Gloeocapsa magma, a cyanobacterium that runs downhill from the ridge and spreads across south- and west-facing slopes. Left alone it holds moisture against the roof surface, which is what starts the corrosion process under a painted or Kynar-coated panel.
Moss and lichen are a different problem. Both have root systems that anchor into surface imperfections and seam overlaps, and lichen in particular produces acids that work on the coating over time. Removing established lichen takes more chemistry and more patience than algae — but it comes off with the right process.
High-pressure cleaning is not the answer on a metal roof. It strips the paint system, forces water into seam laps and penetrations, and can deform lighter-gauge panels. The correct approach is low pressure, the right dwell time, and a cleaning solution matched to coated metal surfaces.
How We Clean Metal Roofs
A process built for metal — not adapted from asphalt shingle cleaning.
Assess the Roof Material & Coating
Standing seam, corrugated, metal shingle, or metal tile — each has its own coating system and its own tolerances. We identify the material and check the coating condition before choosing chemistry or pressure settings.
Protect the Surroundings
Landscaping, gutters, and any HVAC or ventilation equipment near the roofline are protected. Metal roofs shed water fast and runoff carries cleaning solution, so we pre-soak everything below.
Apply Low-Pressure Treatment
A cleaning solution formulated for coated metal surfaces is applied at low pressure. It is left to dwell and work on the algae, moss, and streaking — chemistry does the work rather than force.
Rinse Thoroughly
Everything is rinsed down from ridge to eave, pushing residue and dead growth into the gutters. We clear the gutters and downspouts so runoff exits cleanly.
Inspect Seams & Penetrations
We walk the perimeter looking at exposed seams, fasteners, and flashing for signs of corrosion or sealant failure that go beyond cleaning — and flag anything worth attention before it becomes a bigger issue.
Metal Roof Types We Clean
Every metal roof system has its own cleaning requirements — here is what we work on:
Standing Seam
The premium metal roofing system. Cleaned at low pressure with coating-compatible chemistry to protect the finish and seam integrity.
Corrugated Metal
Common on older homes, outbuildings, and agricultural structures. Algae and rust staining removed without damaging the galvanized coating.
Metal Shingles & Tiles
Metal roofing designed to resemble shake, slate, or clay tile. Soft washed to remove moss and streaking from the profile without forcing water into the overlaps.
Exposed-Fastener Panels
Screws and washers are common failure points. We clean the panel surface and flag any fasteners showing rust or sealant failure.
Stone-Coated Metal
Stone chip coatings require extra care — high pressure strips the aggregate. Low pressure preserves the coating while removing the growth underneath.
Why It Matters to Use the Right Process on Metal
Coating-Safe Chemistry
We use solutions compatible with painted and Kynar-coated metal — not the same bleach formulas used on asphalt shingles.
Low-Pressure Only
High pressure deforms panels, strips paint, and forces water into seam laps. We never use it on metal roofing.
Root-Level Algae & Moss Kill
Growth is killed at the spore and root level so results last — not just surface-rinsed to come back faster.
Corrosion & Seam Inspection
We flag fastener rust, failing sealant, and early corrosion so you know before a small issue becomes a costly one.
Eco-Safe Runoff Management
Biodegradable cleaning solutions and careful runoff management protect your landscaping and the watershed below.
Fully Insured & Roof-Trained
They were the first company I found who understood that you can't treat a standing seam roof the same as shingles. Professional, careful, and the result was exactly what we needed.— Rebecca T., Bellevue, WA · Metal Roof Cleaning
Metal Roof Cleaning Cost in Seattle
Metal roof cleaning is priced by square footage, roof pitch, and the degree of growth. Standing seam systems with significant moss or lichen establishment take more time and chemistry than a lightly algae-stained corrugated roof. We provide transparent quotes before any work begins.
Roof Size & Pitch
Square footage and slope directly set the scope, the time required, and the safety setup needed.
Growth Severity
Light algae streaking cleans quickly. Established moss with root systems, or lichen, requires longer dwell time and more chemistry.
Bundle Discount
Metal roof cleaning pairs well with gutter clearing and house washing. Combining services on one visit is the best value.
The fastest way to an accurate price is a free quote. We respond within 24 hours — often same day.
Frequently Asked Questions
Can you pressure wash a metal roof?
Not in the traditional sense. Metal roofing — standing seam, corrugated, and metal shingles — is durable but its protective coatings and paint systems are not. High pressure strips the coating, forces water into seam overlaps, and can dent lighter-gauge panels. We use controlled low pressure and the right chemistry, which cleans the surface without damaging what protects it.
What is the black streaking on my metal roof?
Almost always Gloeocapsa magma, a cyanobacterium (algae) that feeds on the limestone filler used in many roofing materials. It spreads downhill, so you typically see it as dark streaks running from ridge to eave. It is not structural damage, but it does hold moisture against the roof surface and accelerates corrosion over time if left untreated.
How often does a metal roof need to be cleaned in the Pacific Northwest?
Every 2–3 years for most homes in our area. The combination of coastal air, tree cover, and the damp climate creates conditions where algae, moss, and lichen establish quickly — especially on north-facing slopes and panels shaded by trees. Keeping it clean prevents the organic growth that traps moisture and leads to premature corrosion.
Will cleaning affect the paint or coating on my metal roof?
Correctly done, no. We use cleaning solutions compatible with painted and coated metal surfaces and low pressure that will not abrade the finish. What would affect the coating is high pressure, abrasive brushing, or bleach at the wrong concentration — none of which are part of our process.
Can you remove rust staining from a metal roof?
Surface rust staining — the reddish-brown streaking that often comes from deteriorating fasteners or flashing — responds to acid-based cleaners designed for metal surfaces. Actual rust on the panel itself is structural and outside the scope of washing; that needs a metal roofing contractor.
Have a question we didn't answer? Call (425) 298-7041or submit a quote request — we respond within 24 hours.
Related Roof & Exterior Services
Metal roof cleaning pairs naturally with these services:
Protect Your Metal Roof Investment
A metal roof is a 50-year investment. Keep it clean, keep the coating intact, and prevent the corrosion that starts under untreated moss. Get a free metal roof cleaning quote for your Seattle or Eastside home — usually same day. We serve Bellevue, Kirkland, Redmond, Sammamish, Bothell, Issaquah, and surrounding communities.
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