Why Roof Pressure Washing Should Be Low Pressure Washing

In this article I am going to talk to more about how much pressure is adequate to properly clean a roof and why high powered roof pressure washing is never a good idea. There’s more than one way to skin a cat, but in this case we don’t want to skin the cat, we just want to give it a good shampoo! Make sure that if you decide to hire a professional roof cleaner that he is using very low pressure!

  1. Pressure Washers and Power Washers produce far too much pressure for any type of roofing system. Some of these units produce 3000 PSI or more! This is enough pressure to not only remove granules from your shingles but also to cut your shingles in half. The average garden hose puts about 40-80 PSI which is all that you need to properly and effectively clean your roof. 3000 PSI is overkill and an unacceptable cleaning method for your roofing system whether it is an asphalt roof, tile roof, cedar roof or even a metal roof. You may say to yourself “I think that the wooden and metal roofs can take the pressure”. The fact is that you may hire the most talented pressure washer in the world and he may make your roof look amazing with his high pressure methods. Although, a Pressure Washer will not kill the algae, it will only blow it all over the place, such as on your siding, car and your neighbor’s home. It will even push the algae deeper in the pores of your roofing system, which for obvious reasons is a “no go”!
  2. Pressure Washing accessories still produce far too much pressure! Another tool out there is a “Pitch Witch” and is a “No Go”. It is a device that is on wheels and travels up and down your roof. It has three nozzles so instead of 3000 PSI it puts out about 1000 PSI, which is still way too much pressure. On top of that it is not killing any of the algae, so you can be sure that your algae will grow back very quickly. This is sometimes called a “gitter” along with many other names, so you must be sure to ask for a Soft Wash Roof Cleaning method! The picture below is of the infamous “Pitch Witch”

What this all boils down to is remembering one thing, to only allow the pressure of a garden hose on your roof!

About Zach Maynard

Massachusetts Certified Roof Cleaner and Exterior Contractor. 1-800-781-1816
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10 Responses to Why Roof Pressure Washing Should Be Low Pressure Washing

  1. L. Mack says:

    I just had a roof cleaner tell me that a pressure washer was best way to clean my roof. I’m glad I found this article before wasting both my money and my roof! Thanks for clarifying that its not the best way to go.

  2. Zach Maynard says:

    I’m glad I got my point across! Good luck with your future soft wash roof cleaning.

  3. Joe Conger says:

    I am former Massachusetts resident, in Florida now. What is the way to go with concrete tiles down here. Even your theories are are appreciated. Off hand I like the sodium percarbonate. Which=Oxyclean which= H2O2 in a powder form. You can find 10lbs on eBay for $30.

    I get up on my old white tile roof when it is dry but will hire a pressure cleaning guy coming 4 days from now with a surface cleaner device. My friend has pool bleach which I may spray on roof before the pressure washer guy comes. Hmmmm…gonna call him up and ask

  4. Zach Maynard says:

    Hi Joe, first off I would not suggest using the Percarbonate on any roof.
    Second I strongly suggest you cancel your appt. for the pressure cleaning.
    I think you may want to reread the article above, it goes into detail about the many reasons it is a mistake.
    If you have any questions please feel free to ask!

  5. Joe Conger says:

    I am very very careful on my roof as I prep it with some bleach and borax. I keep very low center of gravity (sit on my butt) as I use a garden pump sprayer bottle. I have ordered a harness because I will be caulking and painting it after this wash. Do you use a harness on some jobs?
    ***** You can send me an e-mail too if you like

    Just by the clean presentation of your website(s) and from the way you come off on your website I could tell you know something about roof cleaning. Babe Ruth said — “It ain’t bragging if you can do it”. If you know someone using your techniques in Ft Lauderdale area please let me know, I will look him up next time. I am kind of committed with this pressure wash guy for this Tuesday and have to do it because code enforcement is not happy with me. I am prepping the roof with pool bleach and tomorrow will do so with pool bleach and borax, I don’t have TSP the sauce. I will keep my pressure wash guy from blasting away. Your outright condemnation of sodium percarbonate got me looking around more and I found Apple Roof cleaning and his sauce. Too bad he is in wrong part of Florida for me.

  6. Zach Maynard says:

    We in fact utilize harnesses, along with respirators, goggles and proper attire. These chemicals are very strong and will not feel good if it gets in your eyes!
    Please be safe up there!

  7. Ronaldo says:

    Zach I heard there is a product called ECO that you spray the roof (I have tile roof) and no wash and cleans amazing. I use pressure washer (3500psi) and I dont want to use it anymore. Do you know this product? Can I find this product in Ft. Lauderdale area? if dont which one you recommend? thank you so much you always give us valiable informations. Please email me asap because I already have a letter to clean the roof

  8. Zach Maynard says:

    There is NO product out there that will be completely eco friendly and kill algae. It is at this time impossible. Stick with what works….bleach.
    Anything else will require yearly application and pressure washing.

  9. Dan says:

    I found that a garden hose and bleach works well on roof tile and cleans just as well as a pressure washer. I use clorox outdoor bleach mixed 50% with water. Spray the roof well getting rid of any major clumps, then spray the bleach heavy with a garden sprayer, let it sit for an hour or so and then lightly wash off. Any bleach residue continues the cleaning. I was amazed at the results and I spent $30 instead of $200.

    • Zach Maynard says:

      You are correct, Bleach is the answer. It is the only method I would ever clean a roof with. Although there is a bit more to it if you would like to do this for a living. I am very glad you didn’t use a pressure washer.

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