An epoxy sealer consists of two parts: a resin and hardener. When these two chemicals come into contact a reaction occurs and produces a hard protective coating that can be used on wood and metal. The resulting coat of epoxy is UV-resistant, durable and hard. There are many different forms of epoxy, but epoxy paints and sealers are best for waterproofing. Unlike other types of waterproof sealers, which need to be reapplied every few years, an epoxy sealer can last indefinitely.
Sand away any existing coating on the wood. Use a sandblaster or large grit sandpaper for large areas. If the wood is new or unfinished, this step is not necessary.
Paint one layer of epoxy onto the wood surface with a paint brush. For large surfaces use a large paint brush. Paint in the same direction as the wood grain. Do not thin the epoxy with a solvent; thinning decreases its waterproofing abilities.
Let the epoxy cure for 36 hours until it is dry. Check with the epoxy instructions for the curing time; it will vary depending on the brand.
Apply a second coat of epoxy and let it cure. One coat of epoxy does not completely waterproof the wood. You will need additional coats.
Sand the epoxy surface with fine-grain sandpaper if you plan to apply an additional UV-resistant coating, varnish or paint. Wipe away any dust before applying the next coat.
If you plan to leave the wood you're waterproofing outdoors, apply an additional UV-resistant coating over the epoxy. UV will break down epoxy over time, making the wood susceptible to water penetration.