All permits as required by this chapter for construction or reconstruction shall automatically expire within six months from the date of issuance thereof in those cases where the construction or reconstruction has not been completed within that period. However, the enforcement agency may extend the expiration date of the permit for a reasonable time.
Source:
Section 18870.10, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=HSC§ionNum=18870.10..