California Code, Health and Safety Code - HSC § 129805

(a) All plans and specifications shall be prepared under the responsible charge of an architect or a structural engineer, or both. A structural engineer shall prepare the structural design and shall sign plans and specifications related thereto. Administration of the work of construction shall be under the responsible charge of the architect and structural engineer, except that where plans and specifications for alterations or repairs do not affect architectural or structural conditions, the plans and specifications may be prepared under the responsible charge of, and work of construction may be administered by, a professional engineer duly qualified to perform the services and holding a valid certificate under Chapter 7 (commencing with Section 6700) of Division 3 of the Business and Professions Code for performance of services in that branch of engineering in which the plans, specifications, and estimates and work of construction are applicable.

(b) The department may exempt projects from the requirements of subdivision (a) where the plans and specifications are not ordinarily, in the standard practice of architecture and engineering, prepared by licensed architects or registered engineers, or both, and are not a component of a project prepared under the responsible charge of a licensed architect or registered engineer, or both. To implement this authority, the department shall adopt regulations, consistent with this section, that specify which projects may be exempted from the requirements of subdivision (a).