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Ask the Experts - Cleaning and Staining Treated Wood

  • What do I use to clean my treated wood deck?
    • Clean annually and keep your deck free from dirt and debris.
    • A solution of liquid detergent and water with a stiff brush will remove mildew and dirt.
    • For hard to clean surfaces, use a deck brightener containing oxalic acid to retain the wood’s natural beauty.
    • Never use household chloride bleaches or foaming cleaners as they can strip the preservatives and damage the wood fibers leaving an unnatural whitewashed appearance.
    • Be careful if using a pressure-washer as excessive pressure may cause damage to the wood.
  • How do I remove the grade stamp on my treated wood deck?

    Light sanding will remove or lighten the grade stamp's appearance.

  • How long do I need to wait to stain or paint my treated wood deck?
    • Allow treated wood to dry prior to application. Test the wood with a few drops of water to see if the wood is dry enough to readily absorb water.
    • Typically, treated wood will be dry and ready for finishing 60 days after installation.
    • Apply the stain to a small portion of the deck to ensure the wood is sufficiently dry.
    • Follow the manufacturer's instructions.
  • What do you recommend I use to stain or paint my treated wood deck or fence?
    • Use a good quality oil-based or water-based stain, or exterior wood water sealant product with UV protection to help prevent the wood from turning gray from exposure to the sun.
    • Apply a water repellent sealer at least every two years.
    • Follow the manufacturer's instructions.
  • How do I remove mold from my deck?

    Mold that you find on pressure treated wood is not an indication of a fungal attack. Mold can grow on the surface of many products including wood (treated and untreated) due to exposure to moisture. To remove mold from your treated deck, use mild soap and water solution and a stiff brush.

    Mold Growth

    Mold and mildew are present everywhere in our environment, both indoors and outdoors. Mold and mildew need four things to thrive: air, water, temperatures between 32 and 120°F, and a food source, conditions that are common wherever humans live, work, and play.

    The best way to minimize mold and mildew growth is to control water and food sources. When it comes to mold or mildew on wood decking, water and organic matter are the primary conditions that enable mold and mildew colonies to thrive. To minimize these conditions, make sure water has the ability to flow away from the deck surface and areas surrounding the deck to lessen the absorption of water. Ensure there is adequate ventilation between deck boards and underneath the deck surface, so water can rapidly evaporate.

    And since both mold and mildew feed on dead or decaying organic matter, so it is important to keep your deck clean of leaves and debris.

    Cleaning Your Deck

    To minimize mold on your decking, clean your deck as often as needed, at least twice each year. Climate conditions vary in different regions of the country and may necessitate more periodic cleaning.

    Remove leaves, debris, and other organic materials that provide a food source for mold.

    If mold is present, there are many commercial products available for cleaning mold. We recommend commercial cleaners containing oxalic acid. For best results, follow the manufacturer’s instructions and use cleaners within their stated shelf life. Do not mix recommended cleaning products together as harmful chemical reactions could occur.

    We do not recommend household chloride bleaches or foaming cleaners as they can strip the preservatives and damage the wood fibers leaving an unnatural whitewashed appearance.

    To maximize application coverage, remove excessive organic growth or clumps prior to applying the cleaner.

    Coatings for High Mold-Prone Environments

    For environments prone to high mold growth, there are commercially available coatings and finishes that seal the wood surface when applied and they should be maintained per the manufacturer’s instructions.

    • Coatings should be applied within one week of cleaning for best results.
    • Prior to coating, properly clean the decking, rinse thoroughly with water and allow to dry completely.
    • Sweep off any pollen and debris.

    Tips for Minimizing Mold

    • Maintain a deck that is dry and clean.
    • Ensure gutters / down-spouts and dryer vents do not discharge directly on decks.
    • Ensure adequate ventilation under and between decking boards.
    • Minimize water puddles under decks and the use of wet mulch up against the deck structure.
    • Cleaning a deck just after the last of the major pollen events (when your car doesn't change color from the pollen anymore) will minimize the seasonal outbreak of mold and mildew.
    • Periodically rinse off your deck using a garden hose with a spray nozzle, especially after the major pollen events. Skilled professionals may use pressure washers with wide fan tips but in the wrong hands, your deck can be damaged. Exercise extreme caution when using pressure washers.
    • Ensure the gaps between the decking boards remain free of debris so that regular rain showers can remove pollen and organic debris between cleanings.
    • Avoid fertilizer over-spray.