Abstract: An extendable deck assembly for a seating area includes a deck portion that is extendable from a base portion to provide a substantially planar support platform. The extendable deck assembly includes a support assembly positioned within the base portion and configured to support a cover plate of the base portion when the deck portion is extended from the base portion. The deck portion may telescopingly extend from the base portion and the support assembly may nest together to facilitate extension and retraction of the support assembly within the base portion. The extendable deck assembly may include a locking mechanism that may secure or lock the extendable deck in the extended position to limit or substantially preclude retraction of the deck portion relative to the base portion. The locking assembly may be part of a guard rail assembly positioned at least partially around the extendable deck portion.