By the EverGlow Exteriors Team

The difference is simple: pressure washing cleans with force (high-pressure water, 1,500-4,000 PSI) while soft washing cleans with chemistry (garden-hose-level pressure plus a solution that kills algae, mildew, and moss at the root). Pressure washing is for hard surfaces like concrete. Soft washing is for everything that can be damaged — siding, roofs, painted wood, screens, soffits.

Use the wrong one and you either destroy the surface or the stains come right back. Here’s the breakdown by surface, and how to tell what your house needs.

How each method actually works

Pressure washing: force

A pump drives water through a narrow tip at high pressure. That force physically scours dirt, grime, and stains off the surface. On concrete, paired with a surface cleaner attachment and detergent pre-treatment, it’s the right tool. On anything softer, that same force gouges wood, cracks vinyl, strips paint, and drives water into places it shouldn’t go.

Soft washing: chemistry

Soft washing applies a diluted cleaning solution — typically sodium hypochlorite blended with surfactants — at low pressure, lets it dwell, and rinses. The solution kills the organism causing the stain instead of blasting off its top layer. That matters because the green and black stuff on Iowa houses is alive: algae, mildew, lichen, moss. Kill it and it’s gone for a year or two. Blast it and the roots regrow in months.

Which method for which surface?

Concrete and pavers: pressure wash

Driveways, sidewalks, patios. Concrete takes pressure well, and Iowa concrete needs it — freeze-thaw pitting traps grime deep in the surface. Details on our pressure washing page.

Siding: soft wash, always

Vinyl, painted wood, stucco, LP — all soft wash. High pressure forces water behind siding panels, and in our climate that water freezes and expands all winter. The green film on shaded north walls (that’s Gloeocapsa and friends) dies to chemistry, not force. See house washing.

Roofs: soft wash only — never pressure

This one isn’t our opinion. The Asphalt Roofing Manufacturers Association (ARMA) says asphalt shingles should never be pressure washed. Pressure strips the protective granules that give shingles their lifespan, and it can void your warranty. The black streaks on roofs are algae, and they die to a soft wash solution. Full explainer: What are the black streaks on my roof? Service: roof washing.

Decks and fences: low pressure plus cleaner

Wood sits in between. High pressure raises the grain and leaves permanent wand marks — you’ve seen the fuzzy, striped decks it produces. The right approach is a wood-safe cleaner with low, controlled pressure. Composite decking is even less forgiving. See deck washing.

Gutters, soffits, fascia: soft wash

The black tiger-striping on gutter faces is oxidation and grime bonded to the aluminum — it needs a dedicated cleaner and hand agitation, not pressure that dents the metal.

Why this matters more in Iowa

Two local realities raise the stakes. First, freeze-thaw: any water driven behind siding, into wood, or under shingles by high pressure will freeze and expand repeatedly from November to March. Damage that would be cosmetic in Texas becomes structural here. Second, our humidity feeds regrowth: humid summers and shaded, damp north walls mean surviving algae roots bounce back fast. Killing growth at the root — the soft wash approach — is the difference between cleaning every 12-24 months and every 4-6.

Is the soft wash solution safe for plants and pets?

Handled correctly, yes. The active ingredient is a diluted bleach solution — the same chemistry municipal water systems use — and the protocol is what makes it safe: pre-wet the landscaping so roots aren’t thirsty for runoff, cover or rinse sensitive plants during application, and rinse everything down after. Pets should stay inside during the wash and until surfaces dry, then it’s business as usual. This is also where hiring matters: the horror stories about dead flower beds come from over-mixed solution and skipped rinses, not from soft washing itself. Ask any company you’re vetting how they protect landscaping — the answer should be specific, not “we’re careful.”

Can I just rent a pressure washer and do both?

Rental units run about $90 a day, and they’re built for one thing: pressure. They can’t meter and apply soft wash solution properly, so DIY “soft washing” usually turns into either full-pressure blasting or an under-mixed spray that does nothing. Flat concrete is a reasonable DIY job if you’re careful. Siding and roofs are not — the damage risk (etched concrete, cracked vinyl, stripped shingle granules, water intrusion) costs far more than hiring it done.

How to vet a company on this exact question

Ask one question: “How would you clean my roof?” If the answer involves a pressure washer, hang up. Then ask for a certificate of insurance — a company that soft washes correctly but carries no liability coverage is still a risk on your property. Here’s exactly what to ask for. Check their Google reviews for jobs like yours, in neighborhoods like yours — we do this work every week across Urbandale, West Des Moines, and Ankeny.

Bottom line

Concrete gets pressure. Everything else gets chemistry. A good exterior cleaning company owns both setups and knows which one your surface needs — most of our jobs use both on the same visit: soft wash the house, pressure wash the drive. If you’re not sure what your place needs, send photos with a quote request and we’ll tell you straight.