Mold thrives where moisture and darkness combine. Mildew is the unfortunate bi-product of mold. This fungus adheres to surface and aside from looking esthetically displeasing. It can be harmful to your health as well. Trex Decks are optimal decks in that they don't splinter or rot, however nothing is sacred when it comes to mold. If you need to remove mold and mildew from your Trex Deck, it's a fairly simple process.
Use a pressure washer to remove as much of the mold as possible.
Mix a solution of 2 parts of vinegar and 1 part of water in a bucket.
Pour the solution on the mold and sprinkle baking soda all over the area.
Allow the vinegar and baking soda to sit on the area for at least 20 minutes.
Scrub the area with a medium to course bristle brush to remove any stains and residual mold and mildew.
Rinse the area with clean water.