Porterville, CA Accessory Structures: ADU Rules (2026)

Municipal Code Section 301.16 sets development, occupancy and design standards for detached, attached, conversion and junior accessory dwelling units citywide. Every ADU needs a permanent foundation and independent exterior access, and no passageway to the primary dwelling is required. For detached units, floor area must be at least 150 square feet and generally caps at 1,200 square feet when accompanying a single-family home, though a converted accessory structure can exceed 1,200 square feet up to its existing footprint. The maximum number of detached ADUs is one per single-family lot, two per an existing multi-family lot, and eight per an existing multi-family lot with an existing multi-family dwelling, and the code caps total dwellings (primary plus ADUs) at four on any single-family-zoned lot.

Setbacks for detached units are four feet on the side, street side and rear yards. Height is capped at 16 feet for a one-story detached ADU, rising to 18 feet within a half-mile of a major transit stop or alongside a multifamily dwelling over one story, and 25 feet for a two-story detached ADU, with a further 2-foot allowance to match a matching roof pitch. One parking space is required per detached ADU on top of the primary dwelling's minimum, but no parking is required within a half-mile of transit, in a historic district, when converting an existing accessory structure, or where street parking permits are unavailable to the occupant.

Attached ADUs cap floor area at 50 percent of the primary dwelling or 1,200 square feet, whichever is greater, use the same 4-foot setbacks, and top out at two stories/25 feet or the base zone's height limit, whichever is lower, with no parking required. Rentals of any ADU created under this section must run longer than 30 days, and for units permitted after January 1, 2025, owner-occupancy of either the primary dwelling or the new detached ADU is required unless the owner is a governmental agency, land trust, or housing organization.

Fire sprinklers are not required in an ADU if not already required in the primary dwelling, and garage conversions do not trigger a driveway-removal mandate.