This section shall not apply to horizontal sliding doors. Existing dead bolts of at least one-half inch in length shall satisfy the requirements of this section. Existing locks with a thumb-turn deadlock that have a strike plate attached to the doorjamb and a latch bolt that is held in a vertical position by a guard bolt, a plunger, or an auxiliary mechanism shall also satisfy the requirements of this section. These locks, however, shall be replaced with a dead bolt at least 13/16 of an inch in length the first time after July 1, 1998, that the lock requires repair or replacement.
Existing doors which cannot be equipped with dead bolt locks shall satisfy the requirements of this section if the door is equipped with a metal strap affixed horizontally across the midsection of the door with a dead bolt which extends 13/16 of an inch in length beyond the strike edge of the door and protrudes into the doorjamb. Locks and security devices other than those described herein which are inspected and approved by an appropriate state or local government agency as providing adequate security shall satisfy the requirements of this section.
Ca. Civ. Code § 1941.3