What clears moss off a north-facing Vancouver wall?

Moss on a north-facing wall in Metro Vancouver is best cleared with a diluted bleach or oxygen bleach solution, followed by scrubbing or low-pressure rinsing — never pressure washing alone, and never painting over it without treatment first.

North-facing walls in Metro Vancouver are the worst-case scenario for biological growth. They receive almost no direct sunlight, stay damp for weeks after rain, and the mild temperatures year-round create ideal conditions for moss, algae, and mould to thrive. In neighbourhoods like North Vancouver, Burnaby Heights, or East Vancouver where mature trees add shade, a north wall can look green within a single wet season if left untreated.

The right cleaning approach depends on what you're dealing with. For moss specifically, a solution of one part household bleach (sodium hypochlorite) to four parts water, applied with a garden sprayer and left to dwell for 15–20 minutes, will kill moss and algae effectively. Oxygen bleach products like OxiClean or Jomax are a lower-fume alternative that work well on wood siding and are less harsh on surrounding landscaping. Wet down any plants near the wall before applying and rinse them after. After the dwell time, scrub with a stiff brush and rinse with a garden hose at moderate pressure. For stucco walls, this process works well without risk of surface damage.

Pressure washing alone is not enough — and this is a critical point. High-pressure washing removes the visible moss but doesn't kill the root structure (rhizoids) embedded in the surface. The moss regrows within months. Chemical treatment is the necessary first step, pressure washing is the rinse. On painted wood siding, keep pressure low (under 1,500 PSI) and hold the nozzle at an angle to avoid driving water behind the cladding.

If you're repainting after cleaning, the surface must be completely dry — in Metro Vancouver's climate, that means waiting 3–5 dry days minimum on a north-facing wall, longer in autumn or spring. Once dry, apply a mould-resistant primer (Zinsser Mold Killing Primer is widely available at local paint suppliers) before your topcoat. For the topcoat, choose a 100% acrylic exterior paint with a mould-resistant additive — Benjamin Moore Aura Exterior and Sherwin-Williams Duration both have built-in mildewcide. Some painters also add a mildewcide additive (available at any paint store for around $10–$15 per bottle) to the topcoat for extra protection on chronic problem walls.

Preventing regrowth is the longer game. Zinc strips installed along the roofline above the wall release zinc carbonate when it rains, which slowly washes down the surface and inhibits moss growth — a common solution on Vancouver roofs that works equally well on walls. Trimming back trees or shrubs that shade the wall and trap moisture against the surface makes a meaningful difference. Annual light cleaning with a diluted oxygen bleach solution in early spring keeps growth from getting established.

For a DIY project, cleaning a single north-facing wall is manageable at ground level. If the moss extends above one storey, or if you're planning to repaint after cleaning, that's the point to bring in a professional — both for the safety of working at height and to ensure the surface prep is done correctly before any paint goes on. Painting over inadequately treated moss is the single fastest way to waste money on an exterior paint job.

If you're planning a full exterior repaint, book early — reputable Metro Vancouver painting crews fill their summer schedules by March. Vancouver Paint Contractors can match you with a local professional for a free estimate through the Vancouver Construction Network at vancouverconstructionnetwork.com.