Yes, it is generally recommended to seal an old deck. Sealing helps protect the wood from moisture, UV rays, and other environmental elements, which can cause damage and deterioration over time. An old deck is particularly susceptible to issues such as drying, cracking, splintering, and discoloration. By applying a sealer, you create a barrier that helps prevent water penetration, reduces the effects of sun exposure, and slows down the aging process of the wood. Sealing an old deck not only enhances its appearance but also extends its lifespan and helps maintain its structural integrity. It is important to properly prepare the deck and choose a suitable sealer to ensure effective protection and long-lasting results.