"Pressure washing" gets used as the name for all exterior cleaning, but there are really two different methods, and using the wrong one is the most common way a cleaning turns into damage. A board or property manager does not need to know the chemistry. It is worth knowing which surfaces get which method, so you can tell whether a contractor's plan makes sense.
The two methods
Pressure washing uses water at high pressure, often several thousand PSI, to strip dirt and grime off a surface. It works because of force. Hot water adds heat, which cuts grease and oil and helps lift organic growth.
Soft washing uses low pressure, about what a garden hose delivers, together with a cleaning solution that kills mold, mildew and algae where they grow. The solution does the work and the water just rinses it away. It works because of chemistry and dwell time, not force.
Neither one is better. Each is right for some surfaces and wrong for others.
Which surfaces get which
- Roofs, all types: soft wash. High pressure strips the protective granules off shingles, and on tile roofs it can crack or loosen tiles and drive water underneath them. The asphalt shingle industry's own guidance is not to use a power washer on shingles at all.
- Stucco and painted walls: soft wash. High pressure can etch stucco, force water behind it, and lift paint.
- Screen enclosures and soffits: soft wash. They are too delicate for force.
- Brick and block: usually soft washing or low to moderate pressure, depending on the condition of the mortar.
- Concrete sidewalks, curbs and valley gutters: pressure and hot water, applied with a surface cleaner so the finish is even.
- Parking decks, dumpster pads and drive-thrus: pressure and hot water, with degreaser for the oil.
- Pavers: moderate pressure, with care around the joint sand.
A property with all of these needs both methods, often on the same day. That is normal, and it is a good sign when a contractor's scope names the method for each surface.
Signs the wrong method was used
- Stripes or swirl marks on concrete. That is what happens when a large flat surface is cleaned with a handheld wand instead of a surface cleaner.
- Etched lines or "wand marks" on stucco or block. The pressure was too high, or the nozzle too close.
- Granules collecting in the gutters or at downspouts after a roof cleaning. The roof was pressure washed.
- Streaks that come back within weeks. The growth was blasted off the surface but not killed, so it regrows from what was left behind.
- Peeling or flaking paint soon after a wash.
What about plants and runoff?
Soft wash solutions are strong enough to kill growth, so they have to be kept off landscaping. A careful crew wets plants down before treating nearby surfaces and rinses them afterwards. On concrete, the concern is the wash water itself: in Orlando, wash water is not allowed to run into storm drains, which flow to the city's lakes without treatment. Ask how the crew will protect both.
Questions to ask before the work starts
- Which method will you use on each surface, and why?
- How will you protect the landscaping, windows and anything painted?
- What will you use on the concrete to get an even finish without stripes?
- Where will the wash water go?
How we choose
Green Earth Power Wash Orlando matches the method to the material on every job: soft washing for roofs, stucco and painted surfaces, and hot water at full pressure only where the surface can take it. See our building exterior washing and roof soft washing pages, or request a free estimate.