For siding, soft washing is the safer choice. It uses low water pressure and a cleaning solution that breaks down algae, mildew and grime, then rinses them away. High-pressure washing can force water behind vinyl panels, scar wood, etch stucco and strip paint. Save high pressure for hard surfaces like concrete driveways and walkways.
Green streaks on the north side of the house, grey film under the eaves, black spots creeping across the siding — every Sudbury homeowner sees it sooner or later. The instinct is to grab a pressure washer and blast it off. On most siding, that instinct is the one thing to avoid.
What is the difference between soft washing and pressure washing?
Pressure washing relies on force. A narrow, high-pressure stream of water knocks dirt off a surface. It is great on concrete, which can take the punishment.
Soft washing relies on chemistry. A cleaning solution is applied at low pressure — closer to a garden hose than a jet — and left to break down algae, mildew, moss and grime. Then everything is rinsed gently. The surface is cleaned without being hit.
Why high pressure can damage siding
Vinyl siding
Vinyl panels overlap like shingles so that rain runs off them. A high-pressure stream aimed upward or at an angle can drive water behind the panels, where it soaks insulation and sheathing and can lead to mould inside the wall. It can also crack older, brittle panels.
Wood siding and trim
Wood is soft. Pressure can raise the grain, gouge visible lines into boards and strip paint or stain, which leaves the wood exposed to moisture.
Stucco and brick
Both are porous. High pressure can etch the surface of stucco, loosen mortar between bricks and push water deep into the wall.
Why soft washing lasts longer
The green on your siding is alive. Algae and mildew grow roots into the tiny texture of the surface. Pressure washing can knock off what you see while leaving the roots behind, so the stain comes back quickly. A proper soft-wash solution treats the growth itself, which is why a soft-washed home generally stays clean longer between washes.
When pressure washing still makes sense
High pressure is the right tool for hard, non-porous surfaces:
Concrete driveways and garage pads
Concrete walkways and steps
Some stone patios, with care
Even then, technique matters: the right nozzle, the right distance and a steady pattern avoid leaving visible lines.
What are the signs your siding needs a wash?
Green or black streaks, often on the north side or behind trees, where the sun rarely dries the walls.
A dull, chalky film that comes off on your fingers.
Dark lines running down from the eaves, where water and debris drip off the roof.
Spider webs and insect nests collecting under soffits and around light fixtures.
Mildew around downspouts, decks and anywhere water splashes back onto the siding.
How do you keep siding clean between washes?
Most of what turns siding green is moisture that never gets a chance to dry. Trimming shrubs and branches away from the walls lets air and sunlight reach the siding. Keeping gutters clear stops water from overflowing down the face of the house. Pointing sprinklers away from the walls helps too. None of this replaces a wash, but it can noticeably stretch the time between cleanings.
What to ask before you hire anyone
What pressure will you use on my siding? The answer for siding should be low pressure.
What cleaning solution do you use, and how do you protect plants? Look for pre-wetting, rinsing and covering delicate plants.
What happens to windows and doors? They should be rinsed so no residue dries on the glass.
Will you walk the property with me first? A good cleaner points out problem areas before starting.
How we soft wash a home
We start with a walk around the property to note stains, delicate plants and anything that needs special care. Landscaping is wetted down, the cleaning solution is applied from the bottom up at low pressure, and after it has had time to work, the house is rinsed from the top down. Windows, doors and plants get a final rinse. You can see more on our soft washing page.
The bottom line
For the walls of your home, think gentle and thorough rather than powerful. Soft washing cleans vinyl, wood, stucco and brick without forcing water where it does not belong — and it treats the growth that keeps coming back.
Frequently asked questions
Is soft washing safe for my plants?
A careful soft wash includes pre-wetting and rinsing the plants and lawn around the house, and covering delicate beds when needed. Ask any cleaner how they protect landscaping before they start.
How often should siding be soft washed?
Many homes only need it every few years. Shaded walls, homes near trees or water, and north-facing sides tend to turn green sooner. We can recommend a schedule after seeing your property.
Will soft washing remove all stains?
It removes organic growth and everyday dirt very well. Rust, paint overspray and some mineral stains need a different treatment, and we will tell you up front if a stain is unlikely to come out.
Can I just use my own pressure washer on low?
You can rinse dust off carefully, but without a proper cleaning solution the algae roots stay behind and grow back quickly. Holding a wand close to the siding can still cause damage, even on a lower setting.
Does soft washing work on stucco and brick?
Yes. Stucco and brick are porous, which is exactly why high pressure can damage them. A soft wash lets the solution do the work and rinses gently.
Get your free soft washing estimate
Tell us about your project and we’ll send you a free, no-obligation quote.
