A deck is considered an accessory structure provided it does not include walls or a roof and further provided it does not include a continuous foundation. In this case, the area of the deck shall not be considered when computing maximum lot coverage. A deck may or may not be attached to the principal structure. A deck must comply with principal structure setbacks in all cases, and it must be installed behind the front facade(s) of the principal structure. If walls or a roof or a continuous foundation are included, the deck shall be deemed to be a part of the principal structure, if attached to same and an accessory structure if detached. If walls or a roof are included, the area of the deck shall be considered when computing maximum lot coverage.