The short answer
Soft washing uses low pressure — under 500 PSI, roughly a garden hose — combined with a cleaning solution that kills algae, mold and mildew at the root. Power washing uses 3,000+ PSI of pure water pressure. Siding, roofs, wood and composite need soft washing. Concrete, brick and stone need power washing. Using the wrong one causes the damage most homeowners blame on weather.
The Difference Is Not Pressure. It Is Chemistry.
Almost every homeowner we meet in Macomb County believes these two services are the same thing at different intensities — like a dimmer switch. They are not. They are two fundamentally different cleaning philosophies, and confusing them is the single most expensive mistake in exterior cleaning.
Power washing removes what is sitting on a surface using mechanical force. Water hits grime hard enough to knock it loose. That works beautifully on concrete, which is dense, porous and effectively indestructible at the pressures we use.
Soft washing removes what is growing on a surface using biology. The organizms staining your siding and roof — algae, lichen, mildew, moss — are alive. A cleaning solution kills them at the root structure. Then low-pressure water rinses the dead organizm away. Nothing is blasted. Nothing is forced.
Here is the part that matters: pressure cannot kill anything. You can blast algae off a north-facing wall and it will look clean that afternoon. The root structure is still embedded in the surface. It regrows in a few months, which is exactly why so many people believe exterior cleaning "doesn't last."
The short version: If the surface can be dented, etched, waterlogged or lifted — it gets soft washed. If it is a solid mineral surface bonded to the ground — it gets power washed.
Which Surfaces Need Soft Washing?
Soft washing is the correct method for anything on your home that is not concrete, brick or stone. In practice, that means most of what you can see from the street.
- Vinyl siding — high pressure drives water behind the panels, where it sits against the sheathing and grows mold you cannot see
- Asphalt shingle roofs — pressure strips the ceramic granules that are the shingle's entire UV protection
- Wood decks, fences and cedar — pressure tears out the soft summer growth between grain lines, leaving a permanently furry surface
- Composite decking (Trex, TimberTech, Azek) — pressure voids most manufacturer warranties outright
- Stucco and Dryvit — pressure cracks the finish coat and lets water into the wall assembly
- Painted surfaces, soffits, fascia and gutters — pressure lifts paint and dents aluminum
- Windows and screens — pressure breaks the seal on double-pane glass, which is a four-figure repair
If your home is vinyl-sided — and in subdivisions across Macomb Township, Chesterfield and Shelby Township, most are — every square foot of that exterior should be cleaned with a solution and low pressure. Not one square foot of it should meet a pressure wand. A proper professional house washing never puts high pressure on your walls at all.
What the Solution Actually Does
A soft wash mix is a diluted cleaning solution with a surfactant that helps it cling to vertical surfaces long enough to work. It is applied at low pressure, allowed to dwell for several minutes while it breaks down the cell walls of the organizm, then rinsed.
The dwell time is the whole job. A crew that sprays and immediately rinses has not killed anything — they have washed the surface with soapy water. This is what "splash-and-dash" means in our trade, and it is why some companies can quote a whole-house wash at a price that barely covers the fuel.
Which Surfaces Need Power Washing?
High pressure belongs on hard, mineral surfaces where the goal is removing embedded material rather than killing something alive.
- Concrete driveways, sidewalks and aprons
- Brick pavers and stone patios
- Garage floors
- Commercial loading docks, dumpster pads and parking structures
- Retaining walls and hardscape
Even here, technique separates results. A wand held too close leaves "zebra stripes" — visible bands where the operator's arc overlapped unevenly. A surface cleaner, which is the round rotating tool you have seen commercial crews walk across a lot, distributes two spinning jets under a shroud and produces a perfectly even finish. Every concrete cleaning job we run uses one. Wand work is for edges and detail only.
A Simple Comparison
| Soft Washing | Power Washing | |
|---|---|---|
| Pressure | Under 500 PSI | 3,000–4,000 PSI |
| What does the work | Cleaning solution | Water force |
| Kills the organizm | Yes, at the root | No — removes surface growth only |
| Typical result lasts | 2–4 years | 6–12 months on organic growth |
| Correct for | Siding, roofs, wood, composite, stucco | Concrete, brick pavers, stone, hardscape |
| Risk if misapplied | Landscaping damage if not pre-wet and rinsed | Etched concrete, destroyed siding, voided roof warranty |
How to Tell What a Company Actually Does
Anyone can put the phrase "soft wash" on a website. Three questions separate the crews that own the equipment from the ones that own a big-box pressure washer:
- "What PSI do you use on siding?" A real answer is a number under 500. Vagueness means a pressure wand with the tip backed off.
- "How long does your solution dwell before you rinse?" There should be a specific answer in minutes. "We rinse right away" means nothing was killed.
- "How do you protect the landscaping?" Correct answer: pre-wet the beds before application and rinse thoroughly after. Plants tolerate the solution fine when they are already saturated; they do not tolerate it applied dry.
What This Looks Like on a Real House
A typical two-story colonial in Southeast Michigan is not one job. It is several methods on one property:
- Roof — soft wash, no exceptions, no walking on shingles that do not need to be walked on
- Siding, soffits, fascia, gutters — soft wash
- Windows and screens — hand detail or low-pressure rinse
- Driveway, walkway, porch — power wash with a surface cleaner
- Deck — soft wash on a lower-strength mix, then a dedicated brightener on wood
A company that shows up and treats all of that with one machine at one setting is going to damage something. Usually the siding, occasionally the roof, and the homeowner rarely connects the two events because the failure shows up months later as a warped panel or a stain that will not come out.
The Bottom Line
Ask which method a company plans to use on each surface before you book. If the answer is the same for your roof and your driveway, keep calling. The correct approach is not a preference or a sales angle — it is determined entirely by what the surface is made of, and any crew doing this properly can tell you exactly why in one sentence per surface.
Want This Handled Properly?
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