The right method depends on the surface and the soil, not on which one sounds tougher. Below you will find how force and chemistry differ, a method for each surface of a typical Kitchener-Waterloo home and how a whole-house job uses both.
In This Article
Force versus chemistry, in one minute
Pressure washing cleans with force. A narrow jet of water, often with detergent, knocks dirt loose. The strength is measured in PSI, or kilopascals in metric.
Soft washing cleans with chemistry. A cleaning mix kills and loosens algae, mould and mildew at low pressure, then gentle water rinses everything away.
The gap shows up on living growth. A jet strips the visible layer and can leave the colony behind, while a mix that kills it at the surface tends to slow the return. On mineral or greasy soil, such as dirt, tire marks and oil, force does the job that a low-pressure rinse cannot.
Low pressure in a soft wash is closer to a strong garden hose than to a pressure washer. The mix does the work, which is why materials that dislike force cope with it so well.
Surface by surface: which method fits
| Surface | Usual choice | Why | Watch for |
|---|---|---|---|
| Vinyl siding | Soft wash | The problem is growth, and force can crack or bow panels | Chalky oxidation is not dirt |
| Painted wood or cedar | Soft wash, gently | A jet raises grain and strips paint | Flaking paint can lift even with a gentle rinse |
| Stucco | Soft wash | Texture holds growth, and a jet pits it and drives in water | Check cracks first |
| Brick | Soft wash or low-pressure rinse | Older mortar erodes under force | White salt is efflorescence, not growth |
| Fibre cement | Soft wash | The paint film protects the board | Open joints and caulk |
| Asphalt shingles | Soft wash only | Force strips protective granules | Roof access is a safety job |
| Concrete driveway, walks and steps | Pressure wash, ideally with a surface cleaner | Dense and tolerant, and oil and tire marks need force | Etching if the wand is held too close |
| Interlock pavers | Pressure wash, moderate | Removes dirt and moss from the surface | Joint sand blows out and needs replacing |
| Wood deck | Soft wash with a brush | Softwood grain fuzzes under a jet | Rot needs repair, not cleaning |
| Vinyl or wood fence | Soft wash, or low pressure on wood | Thin material and old paint | Stain and paint can strip |
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Which soil needs which method
- Green film, black streaks, mildew, lichen and pollen film: soft washing.
- Mud, grime, tire marks, oil and old gum on hard surfaces: pressure washing, sometimes with a degreaser or heat.
- Rust, efflorescence and hard-water scale: neither. These need a specialty cleaner chosen for the stain, so ask before anyone sprays.
Waterloo Region and Guelph have hard groundwater, so mineral spotting on glass after any wash is common. Windows are best done as their own step.
Jobs that use both
Most whole-house cleaning uses each method where it fits. A typical order is:
- Soft wash the roof, walls, trim and other delicate surfaces first, because drips and rinse water fall to the ground.
- Pressure wash the driveway, walkway, steps and patio next, so they are not re-dirtied.
- Clean the windows last, after the rinse water has stopped spotting the glass.
D&D lists soft washing from $350 and pressure washing from $350 for typical Kitchener-Waterloo homes. The two are separate services with separate written quotes, so you can book one or both.
Choose soft washing if, choose pressure washing if
Choose soft washing if the surface is siding, stucco, painted wood, brick or a shingle roof, if the problem is green, black or slimy, or if you want the wall protected from force.
Choose pressure washing if the surface is concrete, interlock or another dense material, if the problem is oil, tire marks or ground-in dirt, or if you are preparing a hard surface for sealing or staining.
Choose both if the house has walls and hard surfaces that both look tired, which is the usual case.
If the budget allows only one this year, match it to the biggest risk. Green walls holding moisture against painted wood point to a soft wash. A slippery, oil-stained driveway that people walk across points to pressure washing.
Questions that reveal the method
- What pressure will you use on my siding, and with what nozzle?
- How do you kill growth on walls and the roof, and how do you protect and rinse plants?
- Which surfaces get pressure washing, and do you use a surface cleaner on flat concrete?
- What insurance do you carry?
Answers should be specific. For the wider comparison, see pressure vs soft washing, and for roofs in particular, soft washing vs pressure washing roofs.
Key Takeaways
- Pressure washing uses force on dense surfaces and greasy soil, while soft washing uses a cleaning mix at low pressure on delicate surfaces with living growth.
- Vinyl, painted wood, stucco, brick, fibre cement and shingles usually call for soft washing, and concrete and interlock usually call for pressure washing.
- Rust, efflorescence and hard-water scale need specialty cleaners, not more force.
- A whole-house job usually uses both, in the order roof and walls, then hard surfaces, then windows.
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