Aluminum siding is durable but its factory finish is permanent — unlike vinyl, you cannot easily re-paint aluminum if the original coating is damaged. Harsh cleaners, high-pressure washing at wrong angles, or abrasive products can oxidize or permanently streak aluminum siding.
What Gets on Aluminum Siding
The most common issues with aluminum siding in Ontario are: oxidation (a chalky white or grey powder as the factory coating ages); black streaks from algae running down from the roofline; green algae or mildew on shaded north and west-facing sides; and general grime buildup.
Dealing with Oxidation
Light oxidation responds well to a diluted all-purpose exterior cleaner applied with a soft brush and rinsed with low-pressure water. Heavy oxidation may require an aluminum-specific cleaner or a light automotive polish applied by hand. Never use steel wool, abrasive pads, or wire brushes — these leave scratches and metal contamination that accelerates further corrosion.
Treating Algae and Mould
Low-concentration sodium hypochlorite solution (1/4 cup bleach per gallon of water with a small amount of dish soap) is effective for algae and mould on aluminum siding. Apply with a soft brush, allow to dwell 5–10 minutes, then rinse thoroughly with low-pressure water.
Avoid High Concentration Bleach: Undiluted bleach can strip the paint binder and accelerate oxidation. Always dilute and test in an inconspicuous area first.
Pressure Washing Aluminum Siding
Keep pressure below 1,500 PSI and use a wide fan tip (40-degree). Most importantly: never spray directly upward into the overlap joints. Aluminum siding is designed to shed water downward — forcing water upward into joints can penetrate behind siding into the sheathing and insulation, causing moisture damage. Always spray at a downward angle following the siding lap direction.
Professional Aluminum Siding Cleaning
D&D Home Services provides professional exterior siding cleaning using appropriate products and pressure settings for each surface type. Contact us for a free estimate.
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 100+ homes in KW Region
