The green and black streaks on the north side of so many DMV houses are algae and mildew, which thrive in our humid summers and shaded lots. The instinct is to blast them off with a pressure washer. On vinyl siding, that's usually the wrong tool.
WHAT'S THE DIFFERENCE?
| Soft Washing | Power (Pressure) Washing |
|---|---|
| Low pressure, similar to a garden hose | High pressure, often 2,500–4,000 PSI |
| Cleaning solution kills algae and mildew | Force removes dirt from the surface |
| Results last much longer; spores are killed | Growth often returns within months |
| For siding, roofs, painted surfaces, stucco | For concrete, brick pavers, some decks |
WHY HIGH PRESSURE AND VINYL DON'T MIX
- Water behind the siding. Vinyl siding overlaps downward to shed rain. Spraying upward forces water behind it, into sheathing and wall cavities, and around windows.
- Cracked or loosened panels. Older, sun-brittle vinyl can crack, and panels can unlock.
- Etched surfaces and stripes. Close nozzles leave visible wand marks.
- Damaged trim and seals. Window caulk, vents and light fixtures get blasted.
Many vinyl siding manufacturers recommend washing with low pressure for these reasons.
HOW A SOFT WASH WORKS
- Plants and shrubs are pre-wet and protected.
- A diluted cleaning solution is applied from the bottom up.
- It dwells for several minutes to kill algae, mildew and lichen.
- The house is rinsed from the top down at low pressure.
- Plants are rinsed again.
Heavy stains sometimes need a second application. Rust, irrigation stains and oxidation (chalky fading) need different treatments.
WHAT IT COSTS
| Home | Typical DMV Soft Wash Cost |
|---|---|
| Townhouse | $250 – $450 |
| Two-story single-family | $400 – $750 |
| Large home or heavy growth | $700 – $1,100 |
Bundling the driveway, walkway and deck usually lowers the total. More prices in our pressure washing cost guide.
Washing before painting is a must, but give the house at least two dry days before paint goes on. Planning to paint the siding? Read painting vinyl siding first.
RELATED READING
PRESSURE WASHING COST GUIDE FOR THE DMV (2026)
What you'll pay to pressure wash driveways, decks, siding, and patios — plus soft wash vs. pressure wash and what's actually worth doing.
CAN YOU PAINT VINYL SIDING?
Vinyl-safe colors, why dark paint warps siding, the prep that matters and real costs.
CURB APPEAL UPGRADES THAT ACTUALLY PAY OFF
Front doors, paint, lighting, washing and walkways — what each costs and what it returns.
Planning a project? See our Pressure Washing service page for scope, process and recent work.
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