What Chemicals & Detergents to Use for Pressure Washing
Water alone only goes so far. The right cleaning solution is what actually removes mold, algae, and grease — here’s what to use on each surface, and what to avoid.
Many people assume pressure washing is all about water and force. In reality, the best results come from pairing moderate pressure with the correct cleaning solution. The right detergent breaks down mold, algae, grease, and grime so you can clean at a lower, safer pressure that won’t damage your surfaces.
The Main Types of Pressure Washing Detergents
Sodium hypochlorite (soft wash solution)
A diluted sodium hypochlorite (essentially a bleach-based) solution is the industry standard for killing mold, mildew, algae, and moss on siding, roofs, and concrete. It’s applied at low pressure — “soft washing” — and left to dwell before rinsing. It must be properly diluted and handled carefully to protect plants and surfaces.
Sodium hydroxide (degreasers)
Sodium hydroxide-based degreasers are alkaline cleaners ideal for cutting through oil, grease, and heavy grime on driveways, garage floors, and concrete. They’re especially effective on automotive stains.
Eco-friendly and biodegradable detergents
For routine cleaning and areas near gardens or waterways, biodegradable detergents offer strong cleaning power with less environmental impact. These are a great default for general house washing when heavy mold isn’t present.
Match the chemical to the surface
Using the wrong solution can etch concrete, discolor siding, strip stain from wood, or kill landscaping. When in doubt, use the mildest effective product and always test a small area first.
Which Solution for Which Surface
- Vinyl & aluminum siding: diluted sodium hypochlorite soft wash or a general house-wash detergent
- Concrete driveways & garage floors: alkaline degreaser for oil, hypochlorite blend for algae stains
- Wood decks & fences: a dedicated, gentle wood cleaner — avoid harsh bleach that can damage fibers
- Roofs: low-pressure soft wash with a properly diluted hypochlorite solution only
- Brick & pavers: mild, surface-safe detergents; avoid acids unless you know the material can handle them
Safety and Environmental Best Practices
- Always read and follow the manufacturer’s dilution instructions
- Wear gloves, eye protection, and appropriate clothing
- Pre-wet and rinse surrounding plants and landscaping to dilute overspray
- Never mix chemicals — combining bleach with other cleaners can create toxic fumes
- Use a downstream injector or soap tip to apply detergent at low pressure
Leave the Chemistry to the Pros
Choosing, diluting, and applying the correct solution for each surface takes experience — and mistakes can be costly. At King’s Castle Home Services, we use professional-grade, surface-appropriate cleaning solutions and proven techniques to get outstanding results while protecting your property and landscaping. Contact us for a free quote on your next exterior cleaning project.
Need professional exterior cleaning services?
If you need professional exterior cleaning services, get in touch with King's Castle Home Services. We proudly serve Toronto and the Greater Toronto Area (GTA).
