How To Pressure Wash A Metal Roof

A metal roof can accumulate all sorts of gunk and debris even if its regularly pressure washed by a professional. The unfortunate truth is that hiring a professional for every cleaning is not feasible for many renters and owners. 

How do I pressure wash my metal roof? Maximize efficiency and minimize time on the roof by having the supplies – and the help – you need:  

  1. Know your roof material
  2. Choose the right pressure washer
  3. Wear protective gear
  4. Know what to use for different stains
  5. Have all tools, supplies and a helper ready before you go up the ladder

This guide is to help instruct anyone and everyone who needs to clean their metal roof with a pressure washer. It’s easier than you think as long as you follow the steps and safety guidelines!

Can I Pressure Wash My Metal Roof by Myself?

There is a reason that many renters and owners turn to professionals for their first roof-cleaning. While some dedicated DIY’ers balk at the prospect of hiring someone to work on their home, many readers remain cautious about climbing the ladder in the first place. 

Safety is always the top priority, but as long as you follow instructions carefully, there is nothing to fear but fear itself. Read on to find out how to clean your metal roof as safely and efficiently as possible.

What Type of Metal Roof Do I Have?

There are different procedures to practice depending on the type of coating on the metal paneling of your roof. There are also different types of materials such as copper or stainless steel, but luckily, we are only aiming to protect the coating on the metal — not the metal itself. 

When you protect the coating, you protect the metal. If you already have exposed metal on your roof, please look into metal roof repair before proceeding.

The most common types of coating for metal roofs are:

  1. Acrylic
  2. Polyester 
  3. Fluorocarbon

Safety Tips And Equipment

Before you begin, make sure you have all the equipment you need before climbing the ladder. In addition to your power washer and detergent, it is helpful to bring a washcloth, a sponge, and a soft-bristled brush. 

A power washer is the main tool we will be using for the job, but having more fine-tuned tools always comes in handy. Our first safety tip is to have everything we need before beginning the job. Proper planning is the most important safety tip we can bestow, and therefore the first. Plan ahead. Now, let’s begin!

Know Your Roof Before You Get Started

It’s important to determine what your roof can handle. There are two different options when it comes to power washers: light-pressure and high-pressure. From there, you have two further sub-options: cold water and hot water. Depending on the buildup on your metal roof, you might need to try a variety of combinations in order to clean the surface. 

With this guide, we hope to eliminate the necessity for trial and error — but no job is perfect. What works for most does not work for all.

Know What You Are Cleaning 

Inquire from the company that manufactured your roof to find out whether or not the panels can tolerate high-pressure power washing. Or, if you know the composition of the roof, check with a roofing expert to learn best practices for that material. If you use something too strong or too hot, you will remove the coating on the panels. Generally, it’s the pressure you have to watch out for. 

A high-pressure hot waterpower wash will eliminate grime faster than any other method but could damage your metal roof. Always do some research on your particular roof before you start. You don’t want to call a repairman for two jobs to avoid calling them for one!

Choosing the Right Pressure Washer

Pressure washers are expensive and are often rented by those who do not want to invest the full sum. A new pressure washer can range from a few hundred dollars to a few thousand dollars, depending on the manufacturer and the intensity. It is wise to buy a power washer if you plan on washing your roof yourself for years to come.

Pressure washers come in two different power types: gas-powered and electric-powered

Gas-powered pressure washers:

  • Are more powerful than electric-powered pressure washers and are often the preferred tool for cleaning a metal roof.
  • Typically generate 3000 pounds per square inch, while electric-powered washers tend to generate around 1400 pounds per square inch. 

How to Use a Pressure Washer

Pressure washers are very simple to set up and operate. A standard garden hose is twisted onto the intake to provide the machine with water, and gas-powered models are filled with gas and oil to provide fuel. Once your pressure washer is fueled up, simply power it up and get to spraying! 

It’s a good idea to test how powerful your pressure washer is before getting on the ladder and spraying your roof. The complications arise when climbing and balancing are added to the equation. Using the pressure washer itself is actually very simple!

Tips for Pressure Washing.

  • It is recommended to use a pressure washer with a 45-degree angle to ensure maximum efficiency when washing. The angle is in the nozzle, so the jet of water sprays downwards while your grip remains normal. A pressure washer with an angled nozzle will guarantee your ability to safely and efficiently wash your metal roof.
  • The best power washers will have an adjustable nozzle to make spraying even safer and easier. As mentioned, the ideal angle for power washing is around 45 degrees — however, different jobs require different applications. You will likely only use a 45-degree angle but finding a power washer with an adjustable is a good idea.

While you may get comfortable up there on the roof after a while, always remember: you want to be on the roof or ladder for only as long as you need to be. 

Don’t rush, but don’t linger either. Equipping yourself with the right tools for the job, like a power washer with an adjustable nozzle, will guarantee you quick and safe results.

Wear Proper Safety Equipment

Your ladder is the most important piece of safety equipment at your disposal. Some jobs might allow you to stand on your roof, whereas some jobs will require all the spraying to be done from the ladder itself. Flat roofs typically allow for walking and spraying, while high pitched (angled) roofs will necessitate staying on the ladder.

Your ladder should be the proper size for the job.

A ladder you use around the house that can reach the top of your roof if fully extended is likely not safe for power washing. The ladder needs to be able to completely reach the roof with plenty of extra roof. 

Never stand on the top of the ladder, and never pass the area marked “Not Safe To Stand.” Your safety is more important than getting the job done quickly. The steps to your ladder should be padded and slip-proof. Ladder steps come with grooves built in that prevent slipping. This feature is especially important when working with water.

Harnesses and helpers

These are a crucial part of any high-altitude project. If you are stepping off the ladder to the roof, wearing a harness is non-negotiable. No matter how flat the roof, the coating can become very slippery when wet with water or detergent. There is no use in having someone hold the ladder if you are going to throw caution to the wind as soon as you step off of it.

Friction boots, goggles, and gloves

These are the final safety tools that are essential to this process. As with harnesses, friction boots are strongly recommended for ladder work and non-negotiable for work on the roof. Friction boots provide extra protection from slipping due to the design and tread of the souls. If you’re going to be doing regular cleaning of your metal roof (which you are) investing in a pair will pay off in no time.

No power washing job should be done without proper protective gear. Water can rebound off surfaces — especially at high pressure — and make its way to your eyes and unprotected skin. Ideally, you will be covered from head to toe, with nothing left exposed to the water and grime that will propel from your roof. Barring complete protection, your eyes must be covered, and your hands must be as slip-free as possible.

Know What to Use for Different Stains

Some jobs only require the use of water and a power washer. Other jobs require detergent and rubbing alcohol in order to free the paneling from years of buildup. To determine what you need for the job besides your power washer, first determine what you are eliminating from your metal roof. The most common roof-dwellers are:

Gunk And Water Deposits

Your most common deposits will be washed away with a good power washer. Typically, cold water will get the job done. The most severe gun and debris will require the use of hot water in order to clean your metal roof.

Start by spraying your roof with a hose or a normal wand attachment. This will give you a better idea of how hard you need to work to rid your roof of gunk and deposits. By the time you break out the power washer, you will know exactly where your problem areas are and how you need to wash them. 

By and large, a good gas-powered power washer will clean any roof. This is especially the case if your roof is cleaned frequently. Typically, roofs cleaned once a year will only require the use of a power washer.

Stickier substances may not come off with a power washer alone. Although the power washer is an essential tool for cleaning a metal roof, you will likely need to implore the aid of other tools and solutions in order to rid your metal roof of gunk and buildup.

What Detergent Should I Use?

Detergents are necessary when buildup reaches a level impenetrable by even a power washer. Household laundry detergents are always a great, noninvasive place to start because they will not harm the coating on your roof. The following recipe is a great place to start when you have found that power washing hasn’t eliminated the problem:

  1. ¼ cup of household laundry detergent
  2. 1 gallon of tap water

How to Use Diluted Laundry Detergent in the Pressure Washer

  • Spread the detergent solution around your roof using a sponge or a washcloth. For large areas, a mop is recommended in order to save time and properly distribute the solution across the metal paneling.
  • Leave the solution to sit on the metal roof for 5 to 10 minutes, depending on the severity of the buildup you are trying to remove. 
  • Once the time is up, simply hose off the solution with normal water. A power washer is not required in order to remove the solution for your roof. 

Tip: This solution also makes an excellent pre-treatment before you start your power washing.

Oil, Paint, Grease, Tar

More heavy-duty stains will require more heavy-duty solutions. It is important to note that solvents should not be applied to the entire roof — unlike detergent solutions — because they can erode your roof just like the stains you are trying to eliminate. Always thoroughly rinse and remove solvents from your roof for this reason.

Rubbing Alcohol (Isopropyl Alcohol), Mineral Spirits, and specially made Roof Cleaners are common choices for removing stains such as oil, paint, grease, tar, and even graffiti in some cases. Because these stains are more serious than typical gunk, they require more caustic solutions.

Rubbing alcohol can be applied directly or diluted into a solution. The alcohol or solution is then applied to the problem areas with a sponge or a washcloth, just like the detergent solution. It’s important to take proper precautions when working with caustic substances. Always wear eye protection when applying alcohol or other solutions and always cover up as much as possible.

Note: Remember to keep on your eye and skin protection for when you are washing off your metal roof. Any of the caustic liquid that you worked hard to shield yourself from can rebound into the air once water is applied. Wearing a facemask is recommended, especially if you are using a purpose-made roof cleaner. Whatever is freed from the roof can potentially get onto your skin and onto/ into your body. S

Mold, Algae, Mildew

If you live in a humid climate, your roof is especially susceptible to the growth of mold, algae, and mildew. Roofs with a greenish tint are likely growing these funky little friends! If your house is in the shade for most or all of the day, you are at even greater risk of growing mold, algae, and mildew. Like all gunk, these microorganisms will start to eat away at your roof’s coating and eventual metal paneling unless regular cleaning is done.

Luckily, it is very simple to treat this pesky growth. The following recipe will remove any and all mold, algae, and mildew:

  • ⅓ cup powdered household laundry detergent
  • 1 quart of household bleach
  • 3 quarts of tap water

It’s highly recommended to use gloves when applying this solution. Bleach, like all caustic chemicals, can damage the skin unless proper precautions are taken.

  1. Mix the solution together thoroughly, then apply with a sponge, rag, or washcloth until the mold is removed. 
  2. Leave it to sit. Thicker buildup might require a longer soak, but always remember that bleach is caustic and can damage your roof’s coating if left on for too long. 
  3. A good rule of thumb is to assume that any buildup will come off with enough elbow grease!
  4. Rinse off with water, using a garden hose or your pressure washer. 

Make sure to wear goggles and a mask to avoid this bleach solution. Cover yourself wherever possible, and ideally wear a long shirt and even neck protection to make sure the bleach does not contact your skin.

Rust Stains

Many people assume rust stains are a sign of a faulty or leaking roof. But this is not the case! There are often small fragments of (harmless) exposed metal that gradually begin to rust over time.

If you are worried that your roof is beginning to leak prematurely, contact the roofers or the manufacturer. However, the majority of cases are harmless and will scrub out just like every other form of stain.

Begin by scrubbing away the affected rusty patches with an abrasive like steel wool. You must remove the rust first before you can access the problem areas themselves. The following is an excellent recipe for heavy-duty rust cleaner: 1 part white vinegar and 5 parts tap water

  1. Apply this solution to a sponge or another non-abrasive pad. 
  2. Lightly scrub the problem areas until the rust is completely gone
  3. Thoroughly rinse and dry the areas to prevent further rusting. 
  4. It is very important to clean this solution for your roof as it WILL cause erosion to the coating and metal if you are not careful. NEVER let this solution sit for longer than 5 minutes, and NEVER let this solution dry on your roof.

It bears repeating; the toughest problems require the toughest answers. Rust stains can be serious and require serious treatment, and therefore serious cleaning when all is said and done. You want your roof to last. Rinse it as best as you can!

Gather All of Your Tools – the Checklist

We already know you’re going to start with a great pressure washer. You will likely want one that is gas-powered to ensure that you have all the power you need to remove any gunk and debris from your metal roof. 

Some jobs can be accomplished with normal cold water from a garden hose, but the most heavy-duty jobs will require hot water and a power washer than can not only power but heat your water.

You will also need a great ladder that is adequately sized for your roof. What works for screwing in a lightbulb in the home will not work for climbing to the top of your house. 

Always make sure that your ladder has padded and protected steps before you climb to your roof and begin washing. Starting with a safe grip from the bottom up will ensure safety and accuracy when power washing. Other musts include: 

  • Don’t forget to find an extension cord that is more than adequate for reaching your roof. Think about the bushes you’ll have to snake around, as well as the safest place to plug in. 
  • You’ll need a functioning garden hose that is long enough to easily reach the roof for rinsing. And don’t forget a good spray nozzle to go along with it. 
  • You may also want to have a small scrub brush on hand or a small scraper, should you find something stubborn that needs a little extra convincing. 
  • Don’t try to do it all alone. Enlist a helper on the ground to hold the ladder and adjust the pressure if and when you need it. 

A reminder about additional safety requirements:

  • Harnesses. Harnesses should be tied to sturdy structures like a chimney in order to guarantee your safety when power washing.
  • Friction boots. Friction boots have specially designed treads on the bottom that make for optimal gripping for otherwise slippery surfaces. 
  • Rubber gloves. Rubber gloves will ensure that your skin is protected and that your grip remains strong.
  • Mask and goggles. Masks and goggles are also crucial for protection from water and from chemical cleaners. 
  • Miscellaneous items. A bandana on your neck and even a hat on your head will do wonders.

Why Power Wash Your Metal Roof?

Not only does regular power washing keep your roof looking its best, but it also ensures your roof will last as long as possible. If you want the paint and enamel coating to remain free of irritants that might otherwise compromise the roof’s integrity, regular cleaning is absolutely essential.

The metal panels that comprise your roof are coated in enamel in order to protect them from the elements. Everything from mildew to acid rain can erode this coating on the way to the metal itself. Once the enamel is gone, the metal paneling will begin to degrade. How quickly the metal degrades depends on the thickness of the paneling and the material that comprises it.

But Aren’t Metal Roofs Rustproof?

Most metal roofs are made with metal that will resist rusting — but only to a certain point. The metal is not completely rust-proof but is protected with a coating just like the enamel that covers the panels themselves. 

Once the coating is eroded, the metal will begin to rust. In layman’s terms, you’re going from a spottily painted roof to a leaking roof. You’re going from protection to decoration. It’s going to be rainy and cold inside!

Regularly power washing your metal roof ensures that your home will look its best and be its best! In short, in order to function as intended, a metal roof needs to be regularly cleaned. Luckily, now you know exactly how to clean it!

Best Power Washers To Use

As we have said, there are gas-powered washers and electric-powered washers, but for metal roofs, it’s really best to stick with gas. That being said, the best all-around power washer is The Simpson MSH3125. Not only is this the best power washer money can buy, but it is also one of the more affordable models at under $400 at the time of writing this guide.

The Simpson boasts incredible power (3200 PSI), in addition to its attractive price-tag. This power washer is powered with a Honda engine to ensure maximum performance and reliability and will be the most dependable item in your garage. 

It’s easy to use and even comes with five different nozzles of varying types to ensure that you can always complete whatever job is at hand. The hose is 25 feet long to ensure easy use with most roofs, and affordable extension hoses are available to high-up and difficult to reach spots. This machine is unbeatable!

Learn From The Pros

It really bears repeating: you don’t need to be a professional to practice safety like a professional. Treat your roof cleaning job like there is a foreman there watching you. 

Would you want someone to climb up on the roof without preparing and without following guidelines to the letter? Of course not! Always be safe and always be careful. Your body will thank you, and so will your roof!

When to Call a Professional

While it is absolutely possible to clean your roof on our own, there are times when you may want to call in the pros. If your roof is damaged or you are worried about its condition at all, it is best to call a professional who is experienced in metal roofing. 

Recent Content