The Core Difference
Pressure washing uses high-pressure water — typically 1,500 to 3,000+ PSI — to blast dirt, grime, and staining off hard surfaces. The force of the water does most of the work.
Soft washing uses low pressure — often 100 PSI or less, similar to a garden hose — combined with a biodegradable cleaning solution. The chemistry does the cleaning; the water is mainly there to rinse. Moss, algae, mildew, and other biological growth are killed at the root level, not just blasted off the surface.
The result with soft washing tends to last longer — because the underlying biology has been treated, not just displaced. A pressure wash that removes moss without killing it leaves the spores and root systems in place to regrow within weeks.
Soft washing cleans deeper and lasts longer for biological growth — moss, algae, mildew, and lichen. Pressure washing is right for hard, non-porous surfaces where abrasive force is safe and effective.
When to Use Pressure Washing
High pressure is appropriate on hard, durable surfaces that won't be damaged by the force of the water:
Concrete driveways & walkways
Embedded dirt, oil stains, and tire marks respond well to high pressure. Concrete is dense enough to handle it.
Paver patios & stone
High pressure lifts moss and dirt from between pavers and off stone surfaces — effectively restoring the look without damage.
Brick (exterior walls, not older heritage brick)
Modern brick and mortar can generally handle controlled pressure washing. Older, softer masonry requires more care.
Concrete block retaining walls
Dense masonry surfaces are well-suited for pressure cleaning.
When to Use Soft Washing
Soft washing is the right choice for any surface where high pressure would cause damage — or where the problem is biological rather than purely surface-level:
Asphalt shingle roofs
High pressure strips the granule layer, voids manufacturer warranties, and can drive water under shingles. Soft washing is the only appropriate method.
Vinyl, Hardie, stucco, and wood siding
Excessive pressure can dent vinyl, crack stucco, strip paint, and force water behind panels. Low-pressure soft washing is safer on all siding types.
Cedar shake roofs and wood decks
High pressure raises the grain, splinters fibres, and permanently damages the surface texture.
Painted surfaces
Any painted exterior — fences, trim, shutters — can be stripped by high pressure. Soft washing cleans without affecting the finish.
Canvas and vinyl awnings
Soft fabrics need extremely low pressure. Cleaning chemistry handles the biological growth; the rinse is gentle.
⚠️ The most common mistake we see
Homeowners renting a pressure washer and turning it on their roof or siding. High pressure on asphalt shingles strips the granule layer and can void your roof warranty. On vinyl siding, it can force water behind the panels into the wall cavity. If in doubt, go lower — or call us for advice before starting.
Does Soft Washing Actually Work?
This is the most common sceptic question — and a fair one. The answer is yes, but with an important nuance: soft washing works by chemistry, not force. The cleaning solution needs dwell time to penetrate and kill the biological growth. After treatment, the dead moss, algae, and lichen wash away naturally with rain over the following weeks, or are rinsed off immediately.
The results also last longer than pressure washing alone. Pressure washing physically removes surface growth but leaves spores and root systems behind. Soft washing kills them, which means the surface stays cleaner for longer before re-treatment is needed.
What About DIY vs Professional?
For soft washing in particular, the professional advantage is significant. Consumer-grade equipment and off-the-shelf solutions work for light maintenance tasks, but professional soft wash systems can apply solutions more evenly and at higher concentrations — which matters when growth is established.
For pressure washing, consumer equipment is more accessible — a rental unit will handle a driveway just fine. The main differences are efficiency and technique. Professionals work faster, cover more ground, and know how to vary pressure and nozzle type by surface.
If you're unsure which method is right for your job, or if the surface is sensitive (roof, older wood, stucco), a professional assessment is worth it before you start.
Quick Reference
| Surface | Recommended Method | Why |
|---|---|---|
| Asphalt shingle roof | Soft wash only | High pressure strips granules and voids warranties |
| Cedar shake roof | Soft wash only | Pressure splinters and raises the grain |
| Vinyl / Hardie siding | Soft wash | Pressure can force water behind panels |
| Wood deck or fence | Low-pressure soft wash | Pressure raises grain and damages fibres |
| Concrete driveway | Pressure wash | Dense surface handles high force safely |
| Paver patio | Pressure wash | Lifts moss and dirt from joints effectively |
| Canvas / vinyl awning | Soft wash | Fabric requires very low pressure |
| Brick (modern) | Pressure wash (controlled) | Dense masonry handles controlled pressure |