Here in northwest Washington, no matter how well we take care of our decks, they end up with green gunk on them every spring. There really is no way to prevent it, but it's important to remove it regularly.
That ugly green slime can make your deck slippery (which is a safety issue), plus it's breaking down the finish. Now that the weather is warming up, it's time to get that deck cleaned so you can enjoy sitting outdoors and soaking up the sunshine.
Often customers tell me they spray their decks down with bleach water. While that may kill the algae and mildew, bleach can be too harsh for wood unless you use a fairly weak solution and wash it off immediately. Don't let it sit, or the wood will get lightened and somewhat fuzzy-feeling. Also, while bleach is an effective algae killer, it doesn't remove grime or grease. And finally, the pH of bleach is too alkali for wood, so you will need to rinse your deck with a weak solution of something mildly acidic such as oxalic acid. If you follow up with a deck brightener product, check that it contains either oxalic or citralic acid
We do offer professional deck cleaning and refinishing, but I realize may of you are home maintenance DIY fans, so here are some of my suggestions for cleaning it yourself:
Options for Cleaning Your Wood Deck
- Sherwin Williams Deckscapes© cleaners
- A solution of 1 gal. water, 1/3 c household bleach, and 1/3 c TSP (tri-sodium phosphate)
- A solution of 1 gal. water and 1/3 c OxyClean
- Apply your solution to the deck with a pump-type garden sprayer and allow it to sit for 10-20 minutes. Avoid getting the cleaning solution on any plants or shrubs surrounding your deck.
- Spray off with a pressure washer set at 900-1000 psi, using a wide angle tip (usually white).
- Keep your nozzle 4"-6" from the deck surface, and use sweeping motions to avoid leaving a striped pattern on the wood or damaging it.
- Follow up with a deck brightener, applied in the same manner as the cleaning solution, and then rinse as above.
- Allow the deck to dry at least a half day or overnight before walking on it and re-positioning the furniture.