For small, low-risk tasks – patio furniture, a backyard grill, or a personal vehicle – a rented consumer-grade pressure washer can do the job. Stick to a wide-angle nozzle (25° or 40°), keep the tip at least 12 inches from the surface, and test on an inconspicuous area first. Too much pressure on soft wood, painted siding, or aged mortar will cause damage that costs more to fix than the cleaning itself.
For anything beyond that – building facades, sidewalks, driveways, storefronts, or any surface you are not 100% sure can handle high pressure – hire a professional. The risks scale fast: a wrong nozzle on brick can blow out mortar joints, and hitting old caulking around windows can force water into wall cavities. Professionals know how to match PSI, flow rate, and detergent to each material, and they carry liability coverage in case something goes wrong.
In New York City there is an additional layer to consider. Pressure washing a sidewalk or building exterior often requires compliance with NYC DEP stormwater regulations, and some co-op and condo boards mandate that only licensed, insured contractors perform exterior cleaning. Before renting a machine and going at it yourself, check your building’s rules and local requirements.