Home Roofing How to Clean a Metal Roof

How to Clean a Metal Roof

by Michael Blount

A metal roof can be one of the most durable and long-lasting roofing materials available today. Metal roofs come in a variety of styles and can provide many benefits over traditional asphalt shingles, including increased longevity, energy efficiency, fire resistance, and improved aesthetics. However, like any other roof, a metal roof requires proper care and maintenance to maximize its lifespan.

Cleaning your metal roof on a regular basis is essential to protect its appearance and performance. Over time, metal roofs are susceptible to dirt buildup, environmental stains, mold growth, and more. If left unaddressed, these issues can start to deteriorate the metal and cause corrosion. A routine cleaning helps maintain the rich coloring and luster of a metal roof, while also preserving its structural integrity.

This comprehensive guide will provide you with the key techniques and best practices for effectively cleaning and maintaining a metal roof. Properly caring for your roof will safeguard your investment and keep your home looking its best.

Understanding Metal Roof Cleaning

To clean and care for a metal roof correctly, it’s helpful to understand what types of metal roofing materials are commonly used, what causes them to get dirty, and how important routine cleaning is for their durability.

Types of Metal Roofing Materials

Today’s metal roofs come in three main types:

  • Steel: The most popular and affordable choice. Can be galvanized with zinc or made of stainless steel for increased longevity. Prone to rusting.
  • Aluminum: Very lightweight and resistant to rust/corrosion. More expensive than steel. Can develop surface dullness over time.
  • Copper: Naturally corrosion-resistant. Forms a patina over time for a distinctive look. The most expensive metal roofing material.

Other less common metals like zinc and titanium are also sometimes used in specialty applications. The specific cleaning method may vary slightly based on your roof’s metal composition.

Common Dirt and Stains

Like any outdoor surface, metal roofs can accumulate a number of different contaminants and stains over their lifetime:

  • Dirt and dust
  • Pollen, leaves, and other debris
  • Mold, mildew, or algae growth
  • Rust stains
  • Environmental stains from rainfall, pollution, bird droppings, etc.
  • Chalking or oxidation of the surface
  • Grease or exhaust stains

Routine cleaning keeps these issues from building up and becoming more difficult to remove.

Why Regular Cleaning is Essential

Cleaning your metal roof at least annually provides several important benefits:

  • Preserves the roof’s cosmetic appearance by removing stains or discoloration. This is especially important for painted metal roofs.
  • Reduces mold, algae, or moss growth that could accelerate corrosion or deterioration.
  • Avoids long-term dirt or rust buildup that can compromise the metal surface.
  • Removes abrasive debris that could lead to scratches or rust down the road.
  • Allows for inspection and early detection of any minor damage or leaks.
  • Helps maintain energy efficiency by getting rid of dark mold or dirt streaks that absorb heat.
  • Extends the lifespan of the roof by keeping the metal in optimal condition.

Basic Methods for Cleaning a Metal Roof

For light cleaning tasks, there are some simple DIY methods you can use for basic upkeep of your metal roof throughout the year.

Using a Garden Hose and Mild Detergent

One of the easiest ways to clean a metal roof is using a regular garden hose and a mild detergent solution. Here are some best practices:

  • Use a standard house-washing detergent that is safe for metals. Avoid harsh chemicals.
  • Mix the detergent with water according to label instructions to make your cleaning solution.
  • Use a spray nozzle attachment on your hose to apply and rinse the cleaning agent. Adjust to a fan pattern.
  • Start washing from the top of the roof and work your way down methodically. Rinse away any loose debris before applying cleaner.
  • Allow the cleaning solution to sit for 5-10 minutes before thoroughly rinsing. Repeat as needed for stubborn areas.
  • Always scrub gently with non-abrasive brushes or cloths to avoid scratching.
  • Rinse the roof until there are no more signs of soap residue.
  • Inspect and make note of any severely stained or corroded areas that require a more intensive cleaner.

Rinsing Best Practices

When using a garden hose to rinse your roof, keep these tips in mind:

  • Rinse at a perpendicular angle to the roof to avoid driving debris into seams.
  • Move the spray nozzle frequently to prevent pooling water.
  • Completely rinse away all detergent residue, which could ultimately stain the metal.
  • Avoid excessive water pressure that could dent softer metals like copper.
  • Rinse down to the eaves and overhangs to remove streaking residue.
  • Inspect roof and siding below for spots you may have missed. Re-rinse if needed.

DIY Safety Precautions

When cleaning your roof yourself, exercise caution:

  • Only use ladders on stable, dry ground and have someone support the ladder.
  • Wear slip-resistant shoes and grip handles on the ladder.
  • Don’t overextend your reach or take risky steps on the roof.
  • Have someone ready to catch the hose if it starts to slip.
  • Avoid cleaning on windy or wet days.
  • Take breaks often if climbing on the roof to avoid fatigue.
  • Carefully rinse away any puddles or slippery areas.

If you don’t feel comfortable cleaning your metal roof yourself, consider hiring a professional. Safety should always come first.

Advanced Cleaning Techniques

For tougher cleaning jobs, you may need to use more advanced techniques or equipment. Here are some options:

Pressure Washing Precautions

Pressure washers can provide much more cleaning power for extremely dirty or stained metal roofs. However, improper pressure washing can also easily damage the roof, so caution is required.

  • Consult your roof’s manufacturer to determine the max PSI rating it can withstand without damage. Softer metals like copper require lower pressure.
  • Use the widest spray nozzle setting to distribute pressure across a broader area.
  • Keep the nozzle at least 1 foot from the roof when spraying. Never point directly at roof seams.
  • Move the nozzle constantly to avoid focusing pressure in one spot.
  • Apply cleaning solution and let sit first to allow chemicals time to work.
  • Avoid excessive overlap when rinsing to prevent buildup in one area.
  • Take extra care around flashing, vents, and joints. They dent more easily.

Using Cleaning Solutions

For more stubborn stains or grime that a regular detergent can’t tackle, specialty cleaners formulated for metal roofs are available. These can be used in conjunction with power washing.

  • Oxalic acid helps brighten copper and remove rust staining. Use dilution rates recommended on the product.
  • Phosphoric acid also brightens copper and removes iron stains. Wear skin protection.
  • Sodium hydrosulfite can help clean tarnished copper. Rinse thoroughly after use.
  • Hydrogen peroxide mixed with baking soda makes a good paste for light stains.
  • Ammonia removes medium staining on aluminum or galvanized steel when mixed with water at a 1:20 ratio. Never mix ammonia and bleach!

Always spot test cleaners first and take safety precautions when using harsh acids or chemicals. Thorough rinsing is critical.

Hiring Professionals

For large or steep metal roofs that are difficult to access or fully clean yourself, consider hiring professional roof cleaners. Look for companies experienced specifically with metal roof cleaning. Professionals have access to:

  • Tank sprayers that allow cleaning larger areas from the ground
  • Industrial lift equipment for safely reaching the entire roof
  • Stronger chemical cleaners not available for consumer purchase
  • Tools like rotary surface scrubbers to agitate stuck-on debris and stains

When hiring out, discuss all materials and methods the company intends to use to ensure they won’t accidentally damage your roof. Get references from past metal roof cleaning jobs.

Maintaining Paint and Finish

Painted or finished metal roofs require some special care when cleaning to avoid damage. The wrong cleaning products can strip away protective coatings.

Understanding Paint Sensitivity

The main issue when cleaning painted metal roofs is that strong alkaline or acidic cleaners can negatively react with metallic paint particles, causing them to dissolve and the paint to strip. Oil-based paints are especially vulnerable.

Even basic cleaners like bleach or ammonia can harm roof paint over time. Abrasive scrubbing can also wear away the painted finish. Being cautious with your cleaning methods helps preserve the roof’s coloring and appearance.

Cleaning Paint

When cleaning a painted metal roof, it’s best to use pH neutral cleaners formulated specifically for use on delicate painted metals. Look for products containing ingredients like:

  • Sodium metasilicate – a paint-safe detergent alternative to harsh surfactants
  • Sodium gluconate – helps chelate and remove metal oxides and mineral deposits
  • Polyethylene glycol – lubricates surface debris to rinse away easily

Avoid any cleaners containing hydroxides, ethers, alcohol, sodium hypochlorite, or solvents which can interact with paint.

Test cleaning agents first on a small, inconspicuous area of the roof to check for any damage to the paint. If no ill effect, you can safely use the product. Always scrub with non-abrasive tools and use minimal pressure. Rinse thoroughly after cleaning.

Preserving Appearance

To keep your roof looking its best after cleaning:

  • Touch up any paint scratches right away to prevent corrosion underneath.
  • Reapply architectural grade reflective roof coatings if they appear worn. This enhances water runoff and reflects sunlight.
  • Have any faded or oxidized areas professionally repainted to restore luster. This may be needed every 8-10 years.
  • Inspect sealants and flashing for deterioration and reseal as required to avoid leaks.

With proper care, routine cleaning, and touch-ups, a painted metal roof can maintain its colorful curb appeal for decades. Preventative maintenance is the key.

Safety and Environmental Considerations

Cleaning your metal roof involves using a variety of tools, equipment, and chemical products. This presents some important safety and environmental factors to consider.

Safety First

When cleaning a metal roof yourself, make safety the top priority:

  • Use caution when working at heights and inspect ladders for defects before use.
  • Wear slip-resistant shoes and consider using a fall protection harness for steep roofs.
  • Have someone assist you when carrying tools up a ladder to keep your hands free.
  • Allow surfaces to cool before scrubbing areas like vent pipes that get hot from the sun.
  • Exercise extreme care when pressure washing to avoid injury from spray splash back.
  • Follow all product label precautions closely when using chemical cleaners and wear gloves/goggles.
  • Check weather forecasts and avoid cleaning on excessively windy days.

It’s often wise to hire professional roof cleaners for difficult or dangerous access situations. Safety should come before cost savings.

Environmental Responsibility

Cleaning products, waste water runoff, and other byproducts can harm the surrounding environment if not handled correctly:

  • Use biodegradable, phosphate-free cleaners whenever possible. Avoid products with VOCs.
  • Contain and properly dispose of any lead-containing debris if cleaning an older roof.
  • Divert all waste water away from plants/grass and into drains/ holding tanks for proper disposal.
  • Sweep up any debris like leaves instead of hosing residue onto the ground. Compost if possible.
  • Allow rinse water to fully dry to avoid pooling and then neutralize if acidic. Check PH before drain disposal.

Being mindful of environmental impact ensures your roof cleaning doesn’t cause ecosystem damage. Contact local regulators for guidelines.

Best Practices for Long-Term Roof Maintenance

While periodic deep cleaning is important for metal roof care, taking some additional maintenance steps year-round helps maximize the roof’s lifespan and beauty.

Regular Inspections

  • Inspect your roof at least twice per year – in spring and fall – for any developing issues.
  • Use binoculars to look for damaged panels, exposed nails, flashes of light indicating pinholes, curling edges, and debris buildup.
  • Take photos over time to compare and spot changes requiring maintenance.
  • Professionally re-inspect every 2 years for in-depth analysis.

Scheduled Cleaning Frequency

  • Clean the roof thoroughly at least once per year. Twice may be needed in rainy climates.
  • Schedule cleanings for spring and fall when algae and moss are most prevalent.
  • Do an additional power wash every 2-3 years for deeper embedded grime.
  • Clean the gutters 2-4 times per year to prevent overflow stains.

Preventing Growth and Corrosion

  • Trim back overhanging tree branches to reduce dampness and debris.
  • Apply moss deterrents like zinc strips soon after roof installation. Re-apply annually.
  • Seal any exposed nail heads or screw holes vulnerable to rusting.
  • Fix dripping HVAC units that can oxidize areas below.
  • Replace old or missing roof flashing that allows water infiltration.

Extending Roof Lifespan

  • Avoid walking on the roof unless necessary to prevent dents.
  • Install foam rubbers under ladder standoffs and walkways to reduce abrasion when access is required.
  • Keep nearby trees trimmed to prevent abrasive wind-blown branches.
  • Apply fresh sealant around vents, joints, screws, etc. every 3-5 years.
  • Consider recoating the roof with reflective paint every decade for added protection.

With vigilant preventative care and cleaning, a metal roof can provide service life expectancies of 50+ years.


Regularly cleaning and properly maintaining your metal roof is one of the best ways to safeguard your investment and keep your home looking its best. While basic cleaning can be performed with DIY methods, you may need professional help for more involved jobs.

By understanding what causes metal roof staining, learning techniques for cleaning different types of metals, taking safety precautions, and practicing preventative maintenance, you can keep your roof in peak shape for decades to come. With proper care applied consistently over your roof’s lifetime, you’ll maintain its structural integrity, weather resistance, and beautiful curb appeal.


How often should I clean my metal roof?

You should clean your metal roof at least once a year. Areas with lots of debris, rainfall, pollution, or tree coverage may need cleaning twice per year.

What are signs my roof needs to be cleaned?

Signs include visible dirt buildup, dark streaks, chalky oxidation, mold or mildew growth, leaves/debris accumulation, and rust stains. A dirty roof looks dull and aged compared to a clean roof.

Can I pressure wash my metal roof?

You can use a pressure washer for cleaning metal roofs, but the PSI should be adjusted based on the roofing material used so as not to damage it. Always use the widest spray nozzle and keep the nozzle 1 foot away to distribute pressure evenly.

How do I clean a rusted metal roof?

For light rust, use a phosphoric or oxalic acid-based cleaner. For heavier rust, gentler abrasives like baking soda or rust converter chemicals may be required. Avoid abrasive scrubbing.

What is the best way to clean roof stains?

For light stains, a mix of water, hydrogen peroxide, and baking soda can be effective. For tougher stains, try specialty cleaners made for metal roofs. Let cleaner sit before rinsing.

Can I walk on my metal roof to clean it?

It’s not recommended to walk on metal roofs as it can dent softer metals. Use ladders and telescoping poles with brush attachments to reach areas safely from the ground if possible.

How do I clean a painted metal roof?

Use only pH neutral cleaners formulated for painted metal roofs. Avoid alkaline/acidic cleaners that could strip the paint. Rinse thoroughly and touch up any paint scratches afterward.

What should I avoid when cleaning metal roofs?

Avoid harsh chemicals like chlorine bleach, abrasive tools that could scratch, excessive water pressure, and walking on the roof unless essential for access.

Should I hire professionals?

For difficult access situations or extremely dirty/stained roofs, hiring professional roof cleaners using tank sprayers or lift equipment can make the job easier and safer.

How can I prevent my roof from getting dirty again quickly?

Routinely clean gutters, trim overhanging branches, reapply protective coatings, and address leaks quickly to prevent buildup of debris, moisture, and stains long-term.

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