California Code, Business and Professions Code - BPC § 5536.25

(a) A licensed architect who signs and stamps plans, specifications, reports, or documents shall not be responsible for damage caused by subsequent changes to or uses of those plans, specifications, reports, or documents, where the subsequent changes or uses, including changes or uses made by state or local governmental agencies, are not authorized or approved in writing by the licensed architect who originally signed the plans, specifications, reports, or documents, provided that the written authorization or approval was not unreasonably withheld by the architect and the architectural service rendered by the architect who signed and stamped the plans, specifications, reports, or documents was not also a proximate cause of the damage.

(b) The signing and stamping of plans, specifications, reports, or documents which relate to the design of fixed works shall not impose a legal duty or responsibility upon the person signing the plans, specifications, reports, or documents to observe the construction of the fixed works that are the subject of the plans, specifications, reports, or documents. However, this section shall not preclude an architect and a client from entering into a contractual agreement that includes a mutually acceptable arrangement for the provision of construction observation services. This subdivision shall not modify the liability of an architect who undertakes, contractually or otherwise, the provision of construction observation services for rendering those services.