Not all exterior cleaning is the same. Using the wrong method on the wrong surface can cause thousands of dollars in damage — blown-out mortar, stripped paint, or cracked siding. Here's how to know which method is right for your project.
What Is Pressure Washing (Power Washing)?
Pressure washing uses a high-pressure water stream (1,500–4,000 PSI) to blast away dirt, grime, mold, oil stains, and paint. "Power washing" is the same thing but uses heated water, which is more effective on grease and oil.
Best for hard surfaces:
- Concrete driveways and sidewalks
- Brick patios and walkways
- Stone retaining walls
- Garage floors
- Commercial parking lots
PSI ranges by surface:
| Surface | Recommended PSI | Risk Level |
|---|---|---|
| Concrete | 3,000–4,000 | Low |
| Brick | 1,500–2,500 | Medium |
| Pavers | 1,500–2,000 | Medium |
| Wood deck | 500–1,200 | High |
| Vinyl siding | 1,000–1,500 | High |
Cost: $0.08–$0.35 per square foot, or $100–$250 for a standard 2-car driveway.
What Is Soft Washing?
Soft washing uses low-pressure water (under 500 PSI) combined with specialized cleaning solutions — typically a mix of sodium hypochlorite (bleach), surfactants, and mildewcides. The chemicals do the cleaning; the water just rinses.
Best for delicate surfaces:
- Vinyl, wood, and fiber cement siding
- Roof shingles (asphalt, tile, slate)
- Stucco and EIFS
- Painted surfaces
- Wood fences and pergolas
- Screens and awnings
Why chemicals instead of pressure?
High-pressure water can:
- Crack or chip vinyl siding
- Drive water behind siding into wall cavities (causing mold)
- Strip granules off asphalt shingles (shortening roof life by years)
- Gouge wood grain on decks and fences
- Blast out mortar between bricks
Soft washing avoids all of this. The cleaning solution kills mold, algae, and bacteria at the root — so surfaces stay cleaner longer than pressure washing alone.
Cost: $0.15–$0.50 per square foot. Slightly higher than pressure washing due to the cleaning solutions.
Quick Comparison
| Factor | Pressure Washing | Soft Washing |
|---|---|---|
| PSI | 1,500–4,000 | Under 500 |
| Cleaning agent | Water only | Chemical solution + water |
| Best for | Hard surfaces (concrete, brick) | Delicate surfaces (siding, roof) |
| How long results last | 6–12 months | 12–24 months |
| Damage risk | Low on concrete, high on siding | Very low on all surfaces |
| Cost per sq ft | $0.08–$0.35 | $0.15–$0.50 |
| DIY-friendly? | Moderate (rental available) | No (chemicals require training) |
When to Use Each Method
Use pressure washing for:
- Driveways — concrete handles high PSI well. Oil stains may need degreaser pre-treatment.
- Sidewalks and patios — concrete, brick, and stone are pressure-safe.
- Garage floors — high PSI removes embedded grime and tire marks.
- Preparation for sealing or staining — pressure washing preps concrete and pavers for sealant.
Use soft washing for:
- House siding — vinyl, wood, fiber cement, and stucco all require soft washing.
- Roofs — never pressure wash a roof. High PSI destroys shingles. Soft wash only.
- Wood decks and fences — low pressure preserves wood grain. Follow with stain or sealant.
- Painted surfaces — soft washing cleans without stripping paint.
- Algae and mold problems — chemical treatment kills organisms at the root. Pressure washing only removes the surface layer, and it grows back faster.
Combine both for:
- Full property cleaning — pressure wash the driveway and walkways, soft wash the house and roof. Most professional companies do both in a single visit.
What to Ask Your Pressure Washing Company
- "What method do you use on siding/roofs?" — If they say "pressure washing" for vinyl siding or roof shingles, find a different company. Soft washing is the only safe option.
- "What PSI do you run on my surfaces?" — A professional should know the right PSI for each surface without hesitation.
- "What cleaning solutions do you use?" — Sodium hypochlorite-based solutions are standard for soft washing. Ask about concentration levels and plant protection.
- "Do you protect landscaping?" — Soft wash chemicals can damage plants. Professionals pre-wet and cover plants before treatment.
- "Do you carry liability insurance?" — Always verify. Damage from incorrect pressure washing can cost thousands to repair.
Common Mistakes
- Pressure washing vinyl siding — drives water behind panels, causing mold in wall cavities.
- Pressure washing roofs — voids manufacturer warranties and shortens shingle life.
- Using too high PSI on wood — gouges the grain, creating a rough surface that splinters.
- Skipping plant protection during soft wash — runoff kills landscaping.
- DIY soft washing — professional-grade chemicals require proper handling, mixing ratios, and disposal. Leave this to pros.
Next Steps
Most professional pressure washing companies offer both methods and will recommend the right approach for each surface on your property. Get quotes from 2–3 companies and ask specifically about their method for each surface.