After many years a decks floor boards may show signs of aging. Wood decks may begin to crack, turn gray, and rot. This is rapidly accelerated if a deck has not been properly maintained with routine staining, cleaning, and sealing. Composite decks can fade and stain over time as well. In many cases the life of a deck frame will outlast the life of the decking because the floor is exposed to the direct effects of the sun and weather.
Before you begin replacing your decking you must inspect the existing frame. Old decks may not have been built to code or may be damaged. Do the joists, beams, and posts appear in good condition free from rot? Was the ledger board properly installed with flashing and bolts? Are the joist hangers and hardware rusted or missing fasteners? What is the joist spacing? If the joist spacing is more than 16" on center you must install new intermediate joists. Stair stringers should be 16" on center for wood decking and 12" on center for most composite decking.
If the deck frame is in poor condition it may be easier to tear down the entire deck and rebuilt it from scratch. Otherwise you can begin removing the existing decking. If the deck was screwed down this will be easy. If the decking was nailed down you will need to use a circular saw to cut the decking between each joist and pry the short pieces up using a claw hammer or pry bar. Your new decking can be installed just as it would be on a new deck.