Whittier, CA Accessory Structures: ADU Rules (2026)

Accessory dwelling units in the incorporated City of Whittier are governed by the city's own zoning code, Whittier Municipal Code Section 18.10.020(I) (most recently amended by Ord. No. 3167, Sept. 23, 2025), not by Los Angeles County. The ordinance expressly states it should be interpreted to affect the requirements of California Government Code sections 66310 through 66342 'but to not authorize more than is legally required.' One ADU plus one junior ADU is allowed on lots with a single-family residence, and detached ADUs are also allowed on multifamily lots (up to eight, not exceeding the number of existing units). Key city development standards: detached new-construction ADUs are capped at 1,200 sq ft (1,500 sq ft on lots of 20,000 sq ft or larger); attached ADUs at 850 sq ft (0-1 bedroom) or 1,000 sq ft (2+ bedrooms), or 50% of the existing primary dwelling. Minimum four-foot side and rear setbacks apply (no setback for conversions). Detached ADU height is 16 feet, rising to 18 feet within a half-mile of a major transit stop or high-quality transit corridor (plus 2 feet for matching roof pitch). One parking space is required unless an exemption applies (within a half-mile of transit, in a historically significant district, etc.). Applications are processed ministerially within 60 days (30 days for preapproved plans, per AB 1332). Whittier does NOT impose owner-occupancy on standard ADUs. Important: ADUs on parcels in a historic district or on a designated historic landmark are subject to the certificate-of-appropriateness review of Municipal Code Chapter 18.84, and ADUs are prohibited in areas the director maps as having insufficient water or sewer service.