Is roof cleaning the same as roof washing?

Before any method comes into it, look at how the documents themselves use the two words. They do not keep them apart.

• GAF, a shingle maker, puts both verbs in one sentence: “Do not power wash the shingles to clean the shingles.”
• The Asphalt Roofing Manufacturers Association (ARMA) writes in its technical bulletin: “DO NOT use a power washer or any type of brush or broom to clean algae from the roof surface.” In the next sentence it says high-pressure washing systems should not be used for any other purpose, “such as cleaning other foreign stains or dirt on asphalt roofing.”
• ARMA's algae and moss bulletin introduces its method as “The most effective method of cleaning algae and moss from a roof” and ends that method with a rinse “with low pressure water.”
• The Metal Roofing Alliance titles its guide as tips for a “Stunningly Clean Roof” and, inside it, writes “NEVER use a power washer.”

Across those documents, clean names the job and wash turns up beside it, often attached to a machine. None of them sets roof cleaning and roof washing up as two different services with two different meanings. Asked as a question about vocabulary, the answer is that the words are used for the same work.

What does change from sentence to sentence is the force. ARMA's power washer and high-pressure washing systems, GAF's power wash, the Metal Roofing Alliance's power washer: in each document, the words that mark the method to avoid on shingle and metal are words about pressure. What each document offers instead is a solution and a rinse. ARMA writes that discoloration “may be lightened by applying a solution of liquid household bleach (sodium hypochlorite) and water,” and the Metal Roofing Alliance moves to a mild detergent when water alone is not enough.

That pairing is where the useful names come from. The low-pressure method that leans on a solution has its own name, set out under soft washing, defined, and the method it is set against is under pressure washing, defined. None of the associations or makers read for this answer draws that line with a pressure figure, which is why the method page explains a soft wash by mechanism rather than a number.

So the question worth asking about any roof estimate, whatever verb it uses, is whether a pressure washer goes on the roof and what solution the roof material calls for. The reasons the roofing documents keep the pressure down are traced in why roof cleaners use low pressure, and a follow-up about the solution, whether soft washing smells, has its own answer.

239 Exteriors names roof cleaning as one of its three services, and its roof flyer calls the method “Safe soft-wash cleaning”: a soft wash that removes algae, mold and stains without damaging your roof. The name joins cleaning, the job's usual name in the documents, with soft wash, the name of the low-pressure method, which is the distinction the roof washing question is really reaching for.

What the name leaves out matters as much. ARMA writes that “The effectiveness of such cleaning is only temporary, and the discoloration may recur.” A cleaning is not a restoration, and the line between the two is drawn in roof cleaning versus roof restoration.