Cal. Health and Safety Code § 16021

Periodically, as the work of construction or alteration progresses and whenever the enforcement agency requires, except as exempt under Section 16010, the inspector on the work and the contractor shall each make a report, duly verified by him or her, showing in his or her own personal knowledge, that the work during the period covered by the report has been performed and that the materials used and installed are in accordance with the approved drawings and specifications, setting forth any detailed statements of fact required by the enforcement agency. “Personal knowledge” as applied to the inspector, means the actual personal knowledge which is obtained from his or her personal continuous inspection of the work of construction in all stages of its progress at the site where he or she is responsible for inspection and when work is carried out away from the site, that personal knowledge which is obtained from the reporting of others of the testing or inspection of materials and workmanship for compliance with plans, specifications, or applicable standards. The exercise of reasonable diligence to obtain the facts is required. “Personal knowledge,” as applied to the contractor, means the personal knowledge which is obtained from the construction of the building. The exercise of reasonable diligence to obtain the facts is required.