Algae and Mold Removal from House Siding in Ontario

If your home's siding has developed green streaks, black spots, or a generally dirty grey appearance that doesn't wash off in rain, you're likely dealing with algae, mold, or mildew. These organic growths are extremely common on Ontario homes — and they require more than a garden hose to remove properly.

Why Siding Gets Algae and Mold

Algae and mold thrive in moisture and shade. Homes with north-facing walls, overhanging trees, or poor drainage near the foundation provide ideal conditions. Ontario's humid summers accelerate growth. Green algae typically appears first as a green tint; black mold (often Cladosporium) appears as dark streaks or patches. Both are living organisms that spread if not treated.

Health and Structural Risks

Mold on exterior siding isn't the immediate indoor health risk that interior mold is — but it can spread to fascia, soffits, and into wall cavities if left untreated for years. Algae holds moisture against siding surfaces, accelerating degradation of vinyl, paint, and wood substrates. Aesthetically, these growths dramatically reduce curb appeal and home value.

DIY Cleaning Risks

Consumer-grade bleach sprays can kill surface mold temporarily but often don't penetrate to eliminate roots in porous surfaces. Overly strong concentrations damage vinyl, kill landscaping, and create safety hazards. Pressure washing mold off siding risks blowing contaminated water into wall cavities and damaging the surface — the opposite of the desired result.

Professional Soft Washing: The Right Solution

Professional soft washing uses biodegradable surfactants and low-concentration sodium hypochlorite at correct dilutions, applied at low pressure. This kills algae and mold at the root level rather than just removing visible growth. The treated area remains cleaner longer because the biological material is dead — not just washed to the next part of the house.

Preventing Regrowth

After professional soft washing, growth typically doesn't return for 1–3 years depending on conditions. To extend the clean period: trim overhanging branches, improve drainage away from the foundation, and ensure gutters are directing water away from siding. Book a soft washing service with D&D Home Services — contact us today.

D&D Home Services Team Exterior Cleaning Experts — Kitchener-Waterloo

With years of hands-on experience cleaning hundreds of homes across Kitchener, Waterloo, Cambridge, and Guelph, our team shares practical, locally-relevant advice you can trust.