Do-it-Yourself Deck Waterproofing

Test the deck to ensure that it is ready for sealant. Old sealant wears off every few years. Pour water on it and see if the deck soaks it up. If it is slow to soak it up, then the sealant hasn't completely worn off yet.

Clean the deck to remove dust and mildew. Spray on a wood cleaner that also kills mold and mildew. Scrub the surface of the deck with a long-handled scrub brush, then rinse it off. If you plan to seal wood that still has a bit of sealant still on it, then you need to use a wood stripper first. Roll it on, rinse it off thoroughly then continue with the cleaner.

Let the deck dry for at least 24 hours.

Paint on a sealant. Fill a painter tray with the liquid, and roll it over the slats with a paint roller following the grain of the wood. Use paintbrushes for the rails and in between the slats. The type of sealant you pick is up to you. Choose a sealant that includes stain or paint if you want the wood colored, one that has UV protection if you want to keep the wood the natural color or one without UV protection if you want the wood to turn gray. Let the sealant dry for several hours before walking on it.