21 C.F.R. § 112.122
What buildings are subject to the requirements of this subpart?
Buildings subject to the requirements of this subpart include:
(a) Any fully- or partially-enclosed building used for covered activities, including minimal structures that have a roof but do not have any walls; and
(b) Storage sheds, buildings, or other structures used to store food contact surfaces (such as harvest containers and food-packing materials).