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Carefully remove the old, damaged deck treads. For boards that are already loose, gently pry them up with a large screwdriver, avoiding excessive force. If a board is tightly secured, do not immediately reach for a pry bar, as this can damage the fragile stair stringers underneath. Instead, use a large screwdriver and a hammer to split the board into pieces by driving the screwdriver beside the nail heads. This action forces the wood grain around the nails to split, allowing the pieces to be removed easily without stressing the stringers. For very stubborn boards that require more force, use a pry bar, but apply leverage as slowly and carefully as possible. It is crucial to prevent damage to the stair stringers, which are the structural pieces below the treads. These stringers are shaped like a sawtooth, with diagonal grain lines that make them very weak and prone to fracturing. Avoid hitting them sideways or applying excessive leverage.