For the purpose of this Section, “accessory structure” shall mean any structure, whether constructed of metal, wood, concrete, fiberglass, plastic or other rigid material, intended or suitable for any accessory use (as defined in the Zoning Code), including without limitation roofed structures, storage buildings, swimming pools, animal shelters or kennels, porches or decks over one hundred (100) square feet in area and/or over six (6) feet in elevation, canopies and awnings. An accessory structure that is attached to the principal building on the subject lot shall be considered part of the principal building.