To repair a wood deck damaged by the weather, look for any signs of rotten wood due to moisture, and repair or replace boards and support posts if the damage is excessive. Pound in any nails that have worked their way out from drying and warping, and sand any loose wood to prevent splinters. Clean the deck and seal the wood to prevent discoloration, mildew and surface erosion because of sun and rain.
Pressure-treated wood is resistant to rot, but moisture causes damage to any wood deck over time. Rot is especially common where wood contacts the ground. Pay particular attention to the area where the deck is connected to the house, and examine supports for rot and attachment hardware for corrosion.
Before applying sealer, the deck should be washed. Use a stiff broom or leaf blower to remove debris, then clean the deck using a commercial deck cleaner. Scrub the deck with a stiff scrub brush or use a pressure washer. Allow the deck to dry for several days before applying any type of finish.
Use a roller, brush or pump sprayer to apply sealer containing either oil or paraffin to keep moisture from penetrating the wood. In addition, it should contain UV blockers or pigment to prevent the sun from turning the deck gray. Look for a sealer that contains a mildewcide if there was mold or mildew present during repairs.