For vinyl, wood, and most painted or coated siding, soft washing is the safer method because it cleans with a chemical solution at low pressure, under 500 PSI, while straight pressure washing runs anywhere from 1,300 to 3,000+ PSI. That’s well above what most siding manufacturers rate as safe, and it’s the reason we soft wash siding on nearly every house call we run in Lexington and save the pressure washer for the hard surfaces underneath it, driveways, concrete, brick pavers.
What’s Actually Different Between the Two
A lot of homeowners assume pressure washing and soft washing are just two speeds on the same machine. They’re not, and the difference matters more than the name suggests.
A pressure washer moves water fast enough to strip paint off a fence. That’s the whole point of it: brute force knocks dirt loose. On concrete or a stone patio, that’s fine. Those surfaces don’t have seams, don’t have a wall cavity behind them, and don’t care about a little extra force.
Siding is a different animal. Vinyl panels overlap and hang loose at the bottom edge so rain runs off the outside face. They were never built to take a direct hit of pressurized water. Push water at the wrong angle, especially upward into a seam, and it goes exactly where it’s not supposed to: behind the panel, into the wall cavity. That moisture doesn’t dry out fast. It sits there, and months later you’re dealing with mold or rot you can’t even see yet, let alone the mildew smell that shows up first.
Soft washing skips the force altogether. We’re running under 500 PSI, closer to a strong garden hose than a jet, combined with a cleaning solution that kills algae, mold, and mildew at the root. Pressure alone just scatters spores around and knocks the visible layer off the surface; the roots stay put and regrow, usually faster than before because the surface got roughed up in the process. Chemistry actually solves the problem; blasting the surface just resets the clock on it.
Why This Matters More in Lexington Than Most Places
This isn’t a generic warning you’d read on any pressure washing site. Lexington’s climate is part of the reason soft washing earns its keep here specifically.
We sit in a humid, limestone-heavy part of the state, and that combination feeds Gloeocapsa magma, the blue-green algae behind the black streaks you’ll see running down north-facing roofs and shaded siding all over town. It’s been steadily spreading north from the Gulf states for years now, and we cover exactly how it behaves on our pressure washing problems page.
What matters for the washing method specifically is that this algae doesn’t sit on top of siding, it roots into the surface texture. A straight pressure blast knocks the visible film off, but spores anchored underneath just regrow. Soft washing’s chemical solution gets down into that texture and kills it at the source, which is the only real way to slow the regrowth. This same principle is why the Asphalt Roofing Manufacturers Association recommends low-pressure, detergent-assisted washing over direct pressure for roofs specifically, protecting the shingle granules while still treating the growth underneath.
When Pressure Washing Is Actually the Right Call
We’re not against pressure washers; half our jobs use one. Knowing where each method belongs is the whole job.
- Concrete driveways, sidewalks, patios: pressure washing is the right tool here; these surfaces can take the force, and it’s the fastest way to lift ground-in dirt and staining
- Brick hardscaping and pavers: similar story, though we still ease off near old or crumbling mortar joints
- Vinyl, wood, fiber cement, and painted siding: soft wash, every time, especially on anything more than 10 to 15 years old
- Asphalt shingle roofs: soft wash only; a pressure washer strips granules right off the shingle and shortens the roof’s life
A contractor telling you they’re pressure washing your siding at “low pressure” is worth a follow-up question about the actual PSI they’re running. Most vinyl manufacturers cap their safe cleaning recommendation around 1,000 to 1,200 PSI, and plenty of rental units start above that before the trigger’s even pulled.
What We Actually Do on a Siding Job
Every siding job starts with a walk-around to check for existing cracks, loose panels, or older, oxidized vinyl that needs extra care. From there we apply a biodegradable soft wash solution, safe for the landscaping underneath, let it sit long enough to break down the algae and mildew at the root, then rinse at low pressure working top to bottom so nothing gets forced upward into a seam. No ladders leaned against the siding, no upward spray angles, no guessing on distance.
It’s slower than cranking a pressure washer to max and blasting the whole house in twenty minutes. It’s also the difference between siding that’s still clean next summer and siding that’s growing black streaks again by August.
Common Questions
Frequently Asked Questions
Curious what soft washing runs for a house your size? Our House Washing page breaks down pricing, and our pressure washing problems hub covers what algae, mold, and bourbon fungus actually look like on Lexington homes if you’re trying to figure out what you’re dealing with first. Or just reach out and send us a photo; we can usually tell you what it’ll take before we ever show up. Want the method itself? Our soft washing page covers how it works on roofs, fences, and decks.