Mold, Mildew & Algae

Remove biological growth safely and keep it from coming back. In this child category we separate mold vs mildew vs algae, map each to the right chemistry (sodium hypochlorite vs oxygen bleach), and set prevention plans—so decks, siding, and fences stay clean, non-slip, and cheaper to maintain over 10 years.

Diagnose First: Mold vs Mildew vs Algae

Chemistry That Works (and When)

  • Sodium hypochlorite (bleach) for fast mold/mildew knock-down; protect plants/metals, control dwell, then rinse thoroughly and normalize pH per product guidance.

  • Oxygen bleach (sodium percarbonate) for fiber-friendlier cleaning and maintenance washes; longer dwell, light agitation, good for periodic upkeep.
    Never mix bleach with acids/ammonia; always test in a small area first.
    Read next: Best Deck Mildew Remover • Safety & dwell specifics: Black Mold on Deck

Process Controls (Soft on Fibers)

Pre-wet adjacent vegetation, tarp delicate plantings, and keep spray in a controlled fan with the grain. Favor soft-wash methods over aggressive pressure to avoid raising grain or driving water into joints. Final-rinse thoroughly and allow full dry-back before finishing.
Read next: Workflow hub: Wood Restoration • If discoloration remains: Remove Stains from Wood Siding & Decks

Prevention: Stop the Comeback

Fix moisture and shade drivers first: redirect sprinklers, clear leaf litter, improve drainage/airflow, and trim vegetation. Choose finishes with good pigment load and built-in mildewcides; set light maintenance cleans before growth re-establishes.
Read next: Algae control on fences: Green Algae on Wood Fence • Ongoing cleaning choice: Best Deck Mildew Remover

When Growth Hides Bigger Problems

Persistent regrowth around posts, ledgers, or bottom boards can signal trapped water and early decay. Diagnose and repair structure before finishing.
Read next: Soft Rot in Deck Posts • Consolidate/patch logic: Wood Rot Consolidants

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