Uncovered decks are subject to damage from fallen tree limbs. Depending on the intensity of the impact, limbs can crack, chip or completely puncture decking boards, rendering them extremely unsafe. To properly replace a damaged decking plank, remove it, cut a new plank to size, then install using decking screws or nails. Allow at least four weeks for the replacement plank to acclimate and dry out before adding stain and sealant.