Soft washing is a low-pressure exterior cleaning method that uses biodegradable cleaning solutions to kill and remove algae, mould, lichen, and organic staining — rather than blasting them off with high pressure. If you've ever had a power washer strip paint, crack mortar, or force water behind siding, soft washing is the alternative your contractor should have recommended instead.
Soft Washing vs. Pressure Washing: The Core Difference
Pressure washing uses high-pressure water (1,500–4,000 PSI) to physically dislodge dirt from surfaces. It's effective on concrete, brick, and heavy machinery — surfaces that can handle the force. Soft washing uses water pressure of 100–500 PSI — roughly the pressure of a garden hose — combined with a cleaning solution that does the actual cleaning work chemically.
The key insight: algae, mould, lichen, and moss aren't just sitting on top of a surface. Their roots penetrate into the material. High pressure removes what's visible but leaves the roots behind — the growth returns within months. Soft washing solutions kill the entire organism including the root structure, which means results last 3–5 years instead of 3–5 months.
| Factor | Pressure Washing | Soft Washing |
|---|---|---|
| Water pressure | 1,500–4,000 PSI | 100–500 PSI |
| Cleaning agent | Water only or mild soap | Biodegradable solutions (SH-based) |
| Kills mould/algae roots | No | Yes |
| Results last | 3–6 months | 3–5 years |
| Risk of surface damage | Moderate–High | Very Low |
How Soft Washing Works
The primary active ingredient in soft washing solutions is sodium hypochlorite (SH) — the same compound in household bleach, but used at controlled concentrations calibrated for the specific surface being cleaned. SH denatures the proteins in algae, mould, mildew, lichen, and bacteria, killing them at the cellular level. A surfactant (soap-like agent) is added to help the solution cling to vertical surfaces and penetrate biofilm. A neutralizer is often applied after to stop the chemical reaction and protect plant life nearby.
The solution is applied with a low-pressure pump sprayer or a dedicated soft washing unit, allowed to dwell on the surface for 10–20 minutes, then rinsed with gentle water pressure. Organic growth turns brown-black as it dies, and most of it simply washes away. Remaining residue fades naturally over the following weeks as it weathers off.
Surfaces Best Suited for Soft Washing
Soft washing is the recommended cleaning method for any surface that pressure washing could damage or that has biological growth requiring more than a surface clean. This includes: asphalt shingle roofs (pressure washing voids most roof warranties), wood and cedar siding, stucco, EIFS/dryvit, painted surfaces, vinyl and aluminum siding, wood decks and fences, and any surface with visible black streaks (Gloeocapsa magma algae) or green/orange lichen growth.
Is Soft Washing Safe for Landscaping and People?
Professional soft washing uses biodegradable formulations that break down quickly in the environment. A professional technician will wet down nearby plants before application, apply the cleaning solution carefully to avoid overspray onto vegetation, and rinse plants after the job. Most professional solutions are designed to neutralize within hours of application when exposed to sunlight and water.
The cleaning solution is not safe for direct contact with eyes or skin during application, which is why professional technicians wear appropriate PPE. After rinsing is complete and the solution has neutralized, treated surfaces are completely safe for people, pets, and nearby plants.
Our Approach: D&D Home Services uses professional-grade biodegradable soft washing solutions on all organic exterior cleaning. We pre-wet and post-rinse all landscaping as standard practice, and our solutions are SH-based formulations calibrated for each specific surface type. Request a free estimate for your home or commercial property.
When to Call for Soft Washing
If you notice black streaks running down your siding or roof shingles, green or orange patches (lichen or moss), a general grey-green discolouration on painted or unpainted surfaces, or visible mildew on shaded areas of siding or fencing — those are all signs that soft washing will get significantly better results than pressure washing or scrubbing. The biological growth will continue to spread and damage the surface underneath if left untreated.
D&D Home Services provides professional soft washing across Kitchener-Waterloo, Cambridge, Guelph, and the surrounding region. Contact us for a free assessment.
Key Takeaways
- ✓ Professional service saves time and delivers better results than DIY
- ✓ Regular maintenance protects your home's value and curb appeal
- ✓ D&D Home Services proudly serves Kitchener-Waterloo and surrounding areas
- ✓ Get a free no-obligation quote — call or book online anytime
Sources & References
- City of Kitchener — Property Maintenance Standards
- Ontario Building Code — Exterior Maintenance Guidelines
- D&D Home Services field experience across 500+ homes in KW Region
