Does the BC Building Code require specific footing depth for deck posts in the Vancouver frost zone?

Green algae stains are extremely common on Metro Vancouver decks due to our persistent moisture and humidity, and they can be safely removed without damaging the wood using oxygen bleach or commercial deck cleaners specifically designed for algae removal.

The key to successful algae removal in Vancouver's climate is understanding that those green, slippery patches thrive in our year-round dampness, especially on north-facing decks that receive limited direct sunlight. The algae isn't just a cosmetic issue — it makes deck surfaces dangerously slippery when wet and indicates that moisture is being retained on the wood surface, which can accelerate decay if left untreated.

Start with oxygen bleach (sodium percarbonate), which is the safest and most effective option for wood decks. Mix one cup of oxygen bleach powder with one gallon of warm water, or use a commercial oxygen bleach deck cleaner like Behr Premium All-in-One Wood Cleaner or Cabot Problem-Solver Wood Cleaner. Apply the solution generously to the affected areas and let it sit for 10-15 minutes — you'll see the algae start to foam and lift away from the wood. Scrub with a stiff-bristled brush (synthetic bristles work better than natural bristles for algae), then rinse thoroughly with a garden hose. For stubborn algae buildup, you may need to repeat the process.

Never use chlorine bleach on wood decking — it damages wood fibres, strips natural oils, and kills surrounding plants when it runs off. Chlorine bleach also doesn't actually kill algae spores, so the green stains return faster. Power washing alone won't remove algae effectively either, as it just spreads the spores around and can drive water deep into the wood grain, potentially causing more moisture problems.

For cedar decks, the oxygen bleach treatment works exceptionally well because cedar's natural tannins help the cleaning solution penetrate. After cleaning, consider applying a cedar brightener (oxalic acid-based product) to restore the wood's natural colour if the algae stains have caused graying. For pressure-treated decks, the same oxygen bleach process works, though PT lumber may require more scrubbing due to its denser surface.

Prevention is crucial in Metro Vancouver's climate. After removing the algae, improve air circulation around your deck by trimming back vegetation that blocks airflow, ensuring gutters aren't overflowing onto the deck, and checking that the deck slopes properly to shed water. Annual cleaning with oxygen bleach in late spring prevents algae from establishing, and applying a penetrating wood stain or sealer after cleaning creates a surface that's more resistant to moisture retention and algae growth.

When to Hire a Professional: If the algae stains cover more than half your deck, if you're dealing with a second-storey deck where safety is a concern, or if the algae has been present for multiple seasons and may indicate underlying moisture or structural issues, consider hiring a deck restoration professional. They have commercial-grade cleaning equipment and can assess whether the algae growth indicates drainage problems or wood decay that needs addressing.

The best time for algae removal in Metro Vancouver is during our drier months (July through September) when the wood can dry completely after cleaning and before applying any protective stain or sealer.

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