man cleaning a metal roof with a pressure washer - feature image

How to Clean Your Metal Roof: A Complete Guide

Metal roofs are fast becoming the first choice of homeowners and business owners alike, and not without good reason. Metal roofs are known for their long lifespans, resistance to harsh weather and fire, and relatively low maintenance requirements. However, if you want to ensure that your metal roof lasts as long as possible in a good condition, you will want to at least clean it every now and then.

Putting in a new roof is a big investment, and there are lots of advantages to choosing a metal roof, but if you don’t put in the bare minimum of maintenance, your roof might not last as long as you had hoped.

A metal roof should be cleaned about once each year to ensure that you don’t get a build-up of dirt and debris, which can have a negative effect on the lifespan of your roof, causing damage to the coating, and allowing the metal to rust.

Why Should You Clean Your Metal Roof?

There are a number of benefits to keeping your metal roof clean and shiny: here are a few good reasons for you to get up there and clean your roof.

To Extend the Lifespan

Metal roofs have a special coating that’s applied when they’re first installed. When dirt and debris accumulate on top of the roof, this coating can become scratched or worn away. This makes the metal roof more vulnerable to damage from rainwater, snow, and wind-driven debris.

To Remove Sticky Substances

Roofs are battered by rain, snow, hail, and wind, which is the carrier of any number of airborne substances that will hit and get stuck on the roof.

Just a few of the most common substances that come into contact with our roofs are pollen, spores, sticks, leaves, dust, dirt, and pollution. Chemicals from the polluted air will stick to the roof and can start reacting with the protective coat if they aren’t removed regularly.

Other items that are blown against the roof, such as sticks and leaves, might not stick, but they can do their own damage to the protective coating when they strike the surface or get scraped around by the wind.

To Keep It Looking Pretty

If you’ve just spent a load of money on a metal roof for your house or business, chances are that you’d like it to look clean, neat, and pretty for as long as possible. Giving it a good once-over each year will prevent your roof from looking dirty and discolored, even if all you’re seeing is a bit of dust on the surface.

Safety First: Take These Precautions Before Cleaning Your Roof

Knowing how to clean your roof is important, but safety is a far more imperative concern. Before you go running up the ladder, excited to get your roof looking spick and span again, make sure you are safe, and able to handle the rigors of roof cleaning without endangering yourself and others.

  • Look at how steep your roof is, and do not attempt to clean it yourself if it is steeper than a 6-in-12-inch pitch (around 26°). The steeper the roof, the more likely you are to slip and fall, especially once the roof is wet with water and cleaning agents. If your roof is steeper than this, you can consider using a garden hose with warm water, and spraying the roof from the ladder or the ground.
steep metal roof
Steep roofs may be to dangerous to clean them yourself.
  • Clean the roof in dry but overcast weather. Direct sun will cause a glare, especially if your roof is light in color, and this could reduce the visibility, endangering you, both while on the roof, and while trying to climb down. Wet weather will only increase your chances of slipping.
  • Never clean the roof when you are alone. Make sure someone is nearby to help you steady the ladder, pass you gear and cleaning items, and call for help if something goes wrong.
  • Use safety gear at all times. It is very easy to think you are secure while walking on the roof, but it only takes one misstep for you to plummet to the ground. Use a safety line and harness to attach yourself to the chimney or some other sturdy part of the roof.
  • Do not clean areas that are too steep or hard to reach. Use a garden hose or pressure hose for these areas, but do not attempt to walk on them or stretch towards them.
  • Ensure you have the correct gear and equipment for the job. Wear shoes with excellent traction, and a good tool belt, and ensure your ladder is sturdy and secure.

How to Clean Your Metal Roof

As you have seen, there are many benefits to cleaning your roof, chief among them a good, long lifespan. However, there is no advantage to rushing off to clean your roof without knowing what you are doing. Cleaning your roof with the wrong materials could cause permanent damage to the paint or the metal, and could even void your warranty, leaving you to deal with the damage out of pocket.

Pressure Wash

This is the easiest method for cleaning your metal roof, but it must be done correctly or you risk damaging the surface. Do not use the highest pressure setting – set your pressure washer to light, and use hot water to dislodge unsightly dirt, debris, and stains from your metal roof.

man cleaning a metal roof with a pressure washer

To clean your roof, start by pouring a bucket of soapy water over the first part you want to clean. Then use a pressure washer to remove any mud, moss, or dirt. Start closest to you and work your way backward in a spiral pattern.

If your roof is steep, use the pressure washer from the ground or the ladder, and if it is flat, walk very carefully on it, and do not step where the roof is wet. Always follow the provided safety tips, and use as much safety gear as possible.

This is the only cleaning method that can be done from the ladder or the ground, so if you have a steep roof and no pressure washer (this can also be done with a strong garden hose and a foam sprayer), rather hire a professional to clean your roof for you.

Cleaning With Laundry Detergent

One way to clean a roof is by using a detergent solution. Fill the bucket with water and add one cup of laundry detergent to it. Use a sponge or cloth to scrub the roof and rinse off any leftover soap residue afterward. This step may be more time-intensive than using a pressure washer, but it will get the job done.

Cleaning With Dish Soap

Create a nice foamy mixture of dish soap and water in a bucket, and scrub the roof with a cloth or sponge until you are satisfied with the results. Rinse well when you are done.

Cleaning With Vinegar

This substance is found on the list of cleaning products for just about everything. It is a miracle worker when it comes to cleaning, and has no harsh ingredients that will damage the protective coating or paint system of your metal roof. Simply mix one cup of vinegar with two cups of water and scrub the roof with a cloth or a sponge. Rinse the roof when done.

Cleaning With Bleach

Bleach is also a very effective cleaning solution, but it is very harsh, and should only be used sparingly and well-concentrated. It works well for killing off the growth of fungus, moss, and mold. Mix one part bleach with eight parts water and apply the solution to the roof with a rag. Allow it to sit for a few minutes before rinsing the roof well. Remember to use rubber gloves when working with bleach.

Things to Remember Before Cleaning Your Roof

  • Be cautious with cleaning products – know which ones are safe and which are harmful to your metal roof. Do not mix chemicals, and do not use stronger concentrations than recommended. Don’t use petroleum-based cleaners, scouring solutions, undiluted bleach, or any kind of paint remover or thinner.
  • Know what equipment you should not use on your metal roof – never use hard scourers, like wire brushes, steel wool, or sandpaper, and always use your pressure washer on the lowest setting.
  • If you find scratches on your roof where the coating is damaged, speak to your roofer to find out how to treat the blemish with the right paint or coating. Using the wrong thing could make the problem worse and void your warranty.
  • If you are unsure of your cleaning method, test it on a small part of the roof that is hidden from sight, and make sure there are no negative effects before moving on to the whole roof.
  • Always put your own safety first – we can’t stress this enough. Hundreds of people die each year from falling off roofs, due to insufficient safety protocols. Don’t add to that statistic – use safety gear, and don’t wash your roof yourself if you don’t feel confident.
  • You can always hire a professional – if your roof is steep, you don’t have safety gear, or you just don’t feel comfortable getting up there to do the job, rather leave it to the pros who have all the necessary equipment and experience.