Roof Washing: Hazards and Considerations

roof washing hazard

Roof washing is probably never on anybody’s top-5 list of ways to spend an afternoon, but it certainly can become a necessary evil.  If it were just a matter of aesthetics, you could almost write it off as vanity and leave your roof to become whatever filthy mess it was destined to become, but that’s not the case.  Historically, there are a number of reasons somebody might want to clean their roof. For example, preventing the buildup of food sources for birds and rodents or preventing chemical buildup that can damage the roof membrane. However, it’s become even more important in recent years with the emergence of energy-efficient buildings and construction.  The build-up of dirt, soot, algae, or other residue can alter the amount of light and heat your roof absorbs or reflects.  Washing it is necessary to keep it as efficient as when it was installed.  However, there are some things you need to consider:

Environmental Concerns

You may have local, state, or national regulations that govern the types of soaps you can use to clean the roof and what to do with the dirty water.  Unfortunately, it’s not as simple as lathering it up and letting it run down a drain.  Know what’s required in your area before beginning. You’ll also want to protect plants, shrubs, and other parts of your building that could be damaged by the run-off, especially if chemicals are being used.


Most likely your warranty will not cover the roof if you’re washing it for aesthetic purposes, but it could if washing it is necessary to keep it as energy efficient as designed.  Know what will and what won’t negate your warranty before starting or hiring a contractor.  If this is the case, the manufacturer/installer of your roof may have recommendations or requirements for you to follow which will dictate what type of brushes to use, what pressure a pressure washer can be used at, and more.  Any damage you cause is going to be on you, so be familiar with this.  As another option, your installer can help you write your cleaning plan or may actually offer cleaning services.  Weigh your options and the possible outcomes.


This is important because people not used to working on roofs may not take the necessary precautions.  Fall protection is going to be a major concern.  If you can do the job from a ladder and maintain three points of contact, you may not need fall protection, but I find it difficult to believe you’ll be able to apply the necessary soaps and water without letting go of the ladder.   If you use an aerial lift or do the work from the roof itself, you are going to need to have fall protection.  On a commercial roof, you may have the benefit of a parapet that meets the requirements for fall protection according to OSHA, but if not, you need to figure out how to protect your workers.  You will not only have open edges where you or your employees will be exposed to a fall but slippery surfaces as well.  Remember, this is a concern on flat roofs as well as sloped roofs.  Personal fall arrest systems may be your best bet, but you need to determine a proper anchor point, ensure your employees are wearing their harnesses and lanyards properly, and ensure they have been trained in the proper use of their fall protection equipment.  If you are not capable of providing all of this, then it may be in your best interest to hire a licensed, trained contractor or to bring your installer back out for the process.  Don’t take this lightly.  Falls are a major cause of occupational deaths and the number one cause in construction. 

Sometimes, things seem simple.  If you need to wash your roof, you may think you just have to throw some soap up there and rinse it off with some water, how hard can it be?  Unfortunately, if you take a moment to look further into it, you could be putting yourself and your employees at risk.  The bottom line: Know what you’re doing or hire somebody that does.

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