effective soft wash roof cleaning

Q: Help me understand soft wash roof cleaning?

This year I am looking to clean my rood shingles a second time, but I keep running across ‘soft wash roof cleaning’.
Back in 2008 I cleaned my shingles with a contractor grade roof cleaner. I mixed the product with water, sprayed it onto the shingles with a pump sprayer, then after 30 minutes rinsed it off with a wide spray on my pressure washer (green tip I think).
I am not sure how a roof shampoo or soft wash is different from what I did years ago. Any ideas?

R Harris from Gulf Shores

A: Soft Wash Roof Cleaning = Chemical Cleaner & Low Pressure Rinse

Great question! We’ve seen an evolution in how the roof cleaning industry talks about roof tile and asphalt shingle cleaning over the last 5 years. Homeowners primary concern about the roof cleaning process is the potential for damage to the roof caused by the water pressure needed to rinse the roof.In the 1990’s (the early years of roof cleaning ) not many specialized roof cleaners had been created so pressure cleaning (using over 500 psi) was the typical approach to blast off the algae and mold from shingles (tile roofs would use even higher pressures sometimes topping 1000 psi). Word of damage caused by this unnecessary amount of pressure spread and thus homeowners began to ask 2 questions to a roof cleaning professional:

    1. Are you using bleach on my roof?
    2. Are you using a pressure washer on my roof

Of course the answer to the first question (are you using bleach? ) should always be NO !

But the answer to are you using a pressure washer really shouldn’t be no. Why? Gravity The reality of roofs being over head means that household water pressure has to work even harder to get to the roof, which means the pressure is lower. Typically a garden hose at roof level will output no more than 65psi in a jet stream, and well under 10 psi in a fan spray.. Essentially useless!

A pressure washer (also called a power washer in some areas) is needed to get a consistent working pressure onto the roof.  Not a crazy roof drilling 3000psi of pressure, but a working pressure between 150 – 200psi.    So to get in front of the question of a pressure washer, the term soft wash roof cleaning   became one of several roof cleaning buzzwords. ( High Volume Low Pressure Rinse, Roof Shampoo and others).    All these terms mean is a sensible use of pressure to rinse the roof without damaging the shingles (or roof tiles).

So to answer your question.  Back in 2008 when you cleaned your roof you actually were performing a ‘soft wash roof cleaning’ !   What’s different now?  Nothing , just better terminology from an roof cleaning industry that is maturing.   So order the same Contractor Roof Cleaner you had back then, and put that green tip on the pressure washer and soft wash your roof again!


  1. R Harris March 4, 2014
  2. Freta A June 22, 2014