If you’ve already purchased a painted metal roof or are looking to purchase one, you may know that metal roofing is a big investment that comes along with a lot of great benefits, including longevity and durability. But what if we told you that one thing left undone could cause your roof to fail or need early replacement?
And that one thing is cleaning your metal roof.
Yes, it’s true. Cleaning your painted metal roof has more benefits than one, but you need to make sure it’s done properly and doesn’t cause harm to the metal or its accessories.
In this article, expect to discover:
- Why a metal roof needs to be cleaned.
- The best methods and tools for cleaning a painted metal roof.
- The methods and tools that should NOT be used to clean a metal roof.
- Important considerations to keep in mind before, during, and after cleaning.
Why Does a Metal Roof Need to be Cleaned?
#1: Extends the life of a metal roof
Like any household or outdoor item, regular cleaning will extend its life. For a metal roof, periodic cleaning helps maintain the integrity of the panels and helps remove any particles on the surface that could degrade the paint system or even the substrate. Luckily, paint systems such as PVDF are durable and engineered to last, but will still benefit from periodic cleaning to keep up the strength of the resin and coating.
#2: Gets rid of the elements stuck on the roof’s surface
Common elements that could get stuck on the surface of a metal roof are:
- Airborne dirt
- Leaves and small sticks
- Spore deposits
- Water stains
- Pollution particles
- Acid rain
- Rust stains
- Mold and mildew
As we mentioned, there are chemicals present in certain atmospheres, such as acid rain and pollution particles, that can cause premature degradation of a metal roofing paint system. One of the easiest ways to determine if your roof is degrading is by inspecting if the paint is chalking. Chalking is the whitish residue that can become visible on a painted or coated metal surface over time.
As a panel is exposed to sunlight and UV rays, the paint system’s resin begins to break down and degrade. Once the resin starts to break down and continues to be exposed to the sun, oxygen, and pollutants, it loses its adhesion to the surface and those degraded particles begin to turn white. These particles will eventually become visible to the naked eye on the metal’s surface. Oftentimes, the difference can be subtle; however, if you swipe the panel with your finger, you can notice the chalky residue on your skin.
Keep in mind, most metal roofing paint warranties don’t cover excessive chalking in the presence of pollutants, which is why it’s important to regularly clean your roof.
There are also elements that won’t create a problem with the paint or the substrate but just makes the roof look dirty, even when it’s actually not.
#3: Maintains the aesthetics of a metal roof
Nobody wants a dirty or unsightly roof, especially since you paid a relatively large sum of money for a metal roof. In other words: You want it to look good for as long as possible.
Simple cleaning once a year will help keep the dirt and other visible elements from making your roof look dirty, moldy, or discolored to the naked eye.
How to Clean a Painted Metal Roof
There are many different methods to clean a metal roof; most of which are dependent on what element needs to be cleaned off of the roof’s surface and the level of severity.
To better understand each method, let’s go through some best practices and common uses for cleaning a painted PVDF metal roof system.
Keep in mind, you do not have to clean your metal roof by yourself; experienced roof cleaning services are available for hire to ensure the safety of all parties. Additionally, the following recommendations are approved for use on Sherwin-Williams PVDF coated metal panels. If your metal roof has a different paint system, such as SMP or acrylic, check with the paint supplier or panel manufacturer first.
Best Metal Roof Cleaning Tools
The following are great tools to clean your metal roof with:
- Soft bristle brush
- Non-abrasive pad
The type of cleaning tools used to clean a metal roof can vary. There are instances where no cleaning tools other than water are necessary. But there are also instances requiring a higher power cleaning agent and a tool to actually wipe/wash the panels with. It just depends.
Best Metal Roof Cleaning Products
Dirt, dust, and other low-grade elements might wash off a roof with something as simple as water from a hose. Feel free to use as much water as necessary until the surface is clean.
This is the cleaning solution that most people need to use when cleaning their metal roof because it’s non-invasive and easy to do. This category includes mild laundry detergents, car washing soap, mild dish soap, and cold or hot commercial/industrial detergents.
- Mix: 1/4 cup detergent (5% detergent solution) per gallon of water.
- Apply solution to surface using a sponge or a washcloth.
- Let stand for 5 to 10 minutes.
- Thoroughly rinse surface with plain water.
Solvents & Petroleum Solvents
Solvents can be used to remove the tougher non-water elements that could come in contact with your PVDF-coated roof, such as oil, paint, grease, tar, and even some graffiti, according to Sherwin-Williams (formerly Valspar). Solvents should be used to clean only affected spots on the roof and should not be used to clean the entirety of the roof. Always check the recommended directions for cleaning on the product’s label and use accordingly.
This class of cleaners includes:
- Rubbing alcohol (Isopropyl)
- Mineral spirits
- VM&P Naphtha
With this group, always keep in mind that you should wear protective clothing, use eye protection, and keep the area properly ventilated because most of these cleaners are toxic. Additionally, keep these solvents away from sparks or open flames, as they are flammable.
Special Metal Roof Cleaning Circumstances
Removing Mildew, Algae, or Mold on Metal Roofing
Metal roofs in humid climates that are subjected to excessive shade might start to show signs of mildew, algae, or mold growth on the surface. Luckily, most mildew, algae, and mold are easy to clean off using the following method:
- Mix: 1/3 cup of powdered laundry detergent + 1 quart of bleach (5% solution) + 3 quarts of water.
- Dip a soft brush or rag in the cleanser and apply to affected areas.
- Lightly scrub the surface until the area is free of mildew or mold.
- Rinse the surface well with plain water.
Removing Rust Stains on Metal Roofing
Depending on where you live, your metal roof could come into contact with metal particles that create rust stains on the paint surface of a metal roof. At first, you might think the roof has a problem or has begun to prematurely corrode, but this is often not the case. It’s actually just in contact with uncoated metal pieces and particles (typically steel) that create rust stains over time.
To remove mild rust stains:
- Remove the particles or pieces that are causing the rust stains.
- Use a mild abrasive cleaner (soft scrub) applied to a non-abrasive pad.
- Use light pressure to work at the stain until it is gone.
- Rinse thoroughly.
To remove severe rust stains:
- Remove the particles or pieces that are causing the rust stains.
- Mix: 5 parts water + 1 part diluted hydrochloric acid OR citric acid OR muriatic acid OR oxalic acid OR vinegar.
- Use a rag to apply to affected spots and use circular wiping motions.
- Rinse immediately after the rust stain has cleared.
- Do not keep solution on the surface for more than 5 minutes.
- Do not let this mixture dry on the surface.
If the rust color persists, it may be more than just an aesthetic issue. Contact your manufacturer or contractor for assistance.
Metal Roof Cleaning Considerations to Remember
#1: Don’t overuse or abuse cleaning agents
Our main recommendation is to just follow the directions supplied to you. Overuse or abuse, such as over-concentrating a cleaning solution, mixing with other chemicals, or using too much of a solution for too long, could lead to damage of the metal or paint system, which will also likely void one or more of your warranties and leave you with the cost of paying for a metal roof replacement. Additionally, overuse or abuse can accelerate corrosion in some instances.
#2: Know products that shouldn’t be used on metal roofing
There are many different chemicals and cleaning materials that will cause damage a metal roof and its paint system. If it’s not listed above, do not use it to clean your metal roof.
Here is a list of products and tools to never use on your metal roof:
- Steel wool
- Wire brushes
- High-pressure power washers
- Scouring powders
- Paint removers
- Paint thinners
#3: Use touch-up paint to address minor imperfections
On occasion, you may find the blemish you are looking to clean is actually a scratch in the coating resulting from a number of things, such as installer error or a small branch hitting the roof during a storm. The thing to remember when applying any sort of touch-up paint is that you follow the manufacturer’s recommendations. Touching up a roof without following the manufacturer’s recommendation could actually make the blemish more unsightly or void the roof warranty altogether.
#4: Test the cleaning method on a non-exposed section before application
If you’re wary of using a cleaning product on your metal roof, test it first. Pick out a spot on the roof that is covered or less noticeable to test the cleaning solution. That way you’ll know if the cleanser works and ensure it doesn’t cause damage to the system.
#5: Protect yourself if you decide to clean the roof yourself
If you decide to clean your metal roof on your own, keep the following considerations in mind:
- Portable ladder safety, as provided by OHSA.
- Safety while walking, sitting, leaning, or working on top of metal roofing.
- Wear the correct shoes that are free of debris and have good traction.
- Always wear fall protection equipment.
- Wearing the right protective clothing, eyewear, and equipment.
- Always check the recommendations on the cleaning product labels.
- Never get on your roof or try cleaning it without at least one other person present.
- Remember that many cleaning solutions are toxic and could cause harm to you, your roof, and items (such as plants) on the ground.
- If you anticipate run-off during cleaning, make sure to cover your surroundings and guide the run-off water elsewhere.
The best way to ensure your metal roof is cleaned properly and safely is to hire a professional roof cleaning business to clean it for you.
#6: When in doubt, hire a professional to clean your roof
If you feel uneasy about getting up on your roof or a ladder to clean it, don’t do it. There are many roof cleaning companies with experienced professionals who can be hired to clean your metal roof for you. Spending a couple of hundred dollars a year is well worth ensuring your safety and your roof’s long-term performance.
Final Thoughts on How to Clean a Metal Roof
Keeping your metal roof clean will help extend its life and the look of it. It seems easy, but there are strict processes of how to do it right.
Always keep in mind:
- Most dirt and dust can be removed with water and/or a mild detergent.
- Follow instructions and use cleaning solutions as directed, especially when using solvents.
- If a cleaning solution has not been approved or mentioned by the paint company or manufacturer, do not use it to clean your roof.
- Hiring a professional roof cleaning service is the best way to ensure your safety.
At Sheffield Metals, we know how important it is to keep your metal roof looking great and performing to its high standards.
We want to help answer your metal roof cleaning questions. Contact us today to speak with one of our knowledgeable metal roofing representatives.