To clean a new wooden deck before applying finish, mix the recommended amounts of trisodium phosphate and OxiClean in a pump sprayer with water, apply the cleaning solution to the deck, and rinse it with a pressure sprayer. Allow the deck to dry before finishing it.
Wear protective boots and eye goggles, and fit a power washer with a 40-degree fan tip before beginning. To protect surrounding foliage, water nearby plants thoroughly or cover the plants with plastic before cleaning the deck. To clean a new wooden deck, mix the recommended amount of trisodium phosphate and oxygen bleach in a pump-style sprayer, and apply the cleaner to a 4x4 foot section of the deck.
Reapply the cleaner as needed to keep the wood wet for five minutes. After five minutes, rinse the area with a pressure sprayer. To avoid etching the wood, maintain a distance of 12 to 18 inches between the tip of the pressure sprayer and the wood, and set the sprayer's pressure to between 500 and 600 psi.
After rinsing the deck, allow it to dry completely before finishing with stain or other finishing products. If a pressure washer isn't available, scrub the deck with the cleaning solution and a firm-bristled scrub brush, and rinse the deck with the garden hose.