Why is it important to stain and seal your new pressure treated deck? Staining and sealing a new pressure treated deck is important for several reasons: Protection: Staining and sealing helps protect the wood from weathering, rot, and insect damage. It forms a barrier that prevents water from soaking into the wood, which can cause it to warp and rot. Appearance: A new pressure treated deck can look very plain and unfinished. Staining and sealing it can give it a finished look