In order to classify, regulate, restrict and segregate the uses of land and buildings, to regulate and restrict the height and bulk of buildings, to regulate the area of yards and other open spaces about buildings, and to regulate the density of population, the following zoning districts are established:

In reviewing a request for zone reclassification pursuant to Chapter 17.20, the planning commission may recommend and the city council may approve an alternative zone or zones that is "more restrictive" than the zone requested in the application and publicly advertised. Zones are considered "more restrictive" in relation to their reverse order as listed in Section 17.15.010, with the exception of the hillside overlay zone (H), which does not contain any uses. For example, the RS-6 zone is "more restrictive" than the RM-2500 zone, but the RS-6 zone is "less restrictive" than the RS-40 zone.

The location and boundaries of the various zones are such as are shown and delineated on the zoning map as adopted originally by Ordinance No. 236 and as subsequently amended, which map, as amended from time to time, is by reference made a part of this title.

The zoning map may, for convenience, be divided into parts and each such part may, for purposes of more readily identifying areas within such zoning map, be subdivided into units and such parts and units may be separately employed for purposes of amending the zoning map or for any official reference to the zoning map.

Changes in the boundaries of the zones shall be made by ordinance adopting an amended zoning map or part of said map or unit of a part of said zoning map, which said amended maps or part or units of parts, when so adopted, shall be published in the manner prescribed by law and become a part of this title.

Where uncertainty exists as to the boundaries of any zone shown upon a zoning map or any part or unit thereof, the following rules of construction shall apply:

Except as provided in this title, no building shall be erected, reconstructed or structurally altered, nor shall any building or land be used for any purpose, except as hereinafter specifically provided and allowed in the same zone in which such building and land is located.

The zones listed in Section 17.15.010 are named according to an orderly arrangement of letters and numbers. The letter designators indicate abbreviated words such as residential (R) and commercial (C). The abbreviated words are spelled out in the second column of the table in Section 17.15.010. The numbers represent the minimum lot size in the single-family zones, and the density (minimum lot area per dwelling unit) in the multiple-family zones. Both minimum lot size and minimum lot area are presented in square-feet units.

To protect the public health, safety and welfare, the city council may adopt an urgency interim ordinance, without a public hearing, which prohibits any uses which may be in conflict with a contemplated zoning proposal which the city council, planning commission, redevelopment agency or the planning division is considering or studying or intends to study within a reasonable time. Such urgency measure shall be adopted in accordance with Title 7, Division 1, Chapter 4, Article 2, Section 65858 of the California Government Code.