The best way to clean algae off urban outdoor furniture on a damp patio involves a safe, effective, and often eco-friendly approach. First, move the furniture to a sunny, open area if possible. For a simple DIY solution, mix equal parts white vinegar and water in a spray bottle. For tougher growth, a solution of one part oxygenated bleach (or a mild, biodegradable outdoor cleaner) to four parts water is highly effective. Always test any cleaner on a small, hidden area first.
Apply your chosen solution generously and let it sit for 10-15 minutes to penetrate and kill the algae. Then, scrub the surface vigorously with a stiff-bristled brush (nylon brushes are gentler on materials than wire). For intricate furniture, an old toothbrush works well. After scrubbing, rinse the furniture thoroughly with a garden hose. For deeply embedded algae on durable materials like concrete or metal, a low-pressure power washer can be used cautiously to blast it away.
Prevention is key for furniture in damp, shaded areas. After cleaning, consider applying a protective sealant suitable for the furniture material. Regularly moving furniture to sunny spots and using breathable, water-resistant covers when not in use will significantly slow algae's return. This combination of targeted cleaning and proactive maintenance will keep your urban outdoor space looking fresh and welcoming.