You want to protect your deck from the weather by either staining, sealing or painting it. Before you do that we recommend you prep accordingly so that stain, sealer or paint will adhere to your wood. This is a before and after picture of a deck we did prepped for finish. We use Sodium Percarbonate to clean and Citric Acid to Neutralize the wood. You should have many years on your deck if you do a little preventive maintenance.