(a) An architectural plan or specification for the construction, enlargement, or alteration of a privately owned building shall be prepared by an Architect or under the Supervision and Control of an Architect unless an engineer may prepare the architectural plan or specification pursuant to §1.210(c) or (e) of this title (relating to Architectural Plans and Specifications) or a Nonregistrant may prepare the plan or specification pursuant to an exemption described in Chapter 1051 of the Texas Occupations Code.(b) For purposes of §1051.606 of the Texas Occupations Code, "multifamily dwelling" means a building containing more than two separate units intended to be used for human habitation where the units are not separated by open space but instead are separated only by walls or partitions.(c) For purposes of §1051.606 of the Texas Occupations Code, "commercial building" means an enclosed structure primarily used for the purchase, sale, or exchange of commodities or services.(d) For purposes of §1051.606 of the Texas Occupations Code, "warehouse that has limited public access" means a building primarily used for the storage of equipment, merchandise, or commodities where:(1) only employees, delivery persons, and other specifically authorized people are routinely expected to enter the building; and(2) persons who enter the building are expected to occupy the building only on a limited basis.