Oakland, CA Accessory Structures: Garage Conversions (2026)

ADUs for Single-Family Homes If you have a Single-Family home , you can add an ADU in one of three ways: Junior ADU (JADU) – Converts existing space inside your home (like a bedroom or garage) into a small unit (500 sq. ft. max). Requires the owner to live on the property. Category One ADU – Converts or rebuilds an existing space (like a garage or basement). No expansions are allowed, except for a small entrance (up to 150 sq. ft.). Category Two ADU – Builds a new attached or detached structure on the property. [...] ADUs for Multi-Family Homes If you own a Multi-Family building (duplex, apartment, etc.) , you may be able to add ADUs in different ways: Category One ADU – Converts non-living spaces (such as storage rooms, attics, or garages) into housing. Category Two ADU – Builds new detached ADUs or converts existing detached structures into ADUs. [...] How Much Does an ADU Cost? The cost of an ADU depends on its type, size, and materials. ADU Types & Cost Per Square Foot (Estimates) Convert existing space (garage, basement): $200-$300 sq/ft Convert existing accessory structure: $300-$650 sq/ft Add to an existing home: $250-$400 sq/ft Build a new detached ADU: $300-$500 sq/ft Prefabricated (modular) ADU: $300-$500 sq/ft State & Local Codes ADUs must follow state and local building codes , including: California Building Codes Oakland Amendments to the California Building Codes Green Building Standards Code (CALGreen) [...] Your application has two main steps : 1. Zoning Approval – Ensures the ADU meets location, size, and height requirements. 2. Building Permit – Verifies that the ADU is built safely and meets Building Codes. [...] Legalize Your Unpermitted ADU – Increase Your Home Value Today! If you have an ADU built without permits, you may qualify for the following: Amnesty from violations of Planning Code standards Delay in enforcement action for unpermitted ADUs like fines, penalties, and orders to remove, modify, or alter your ADU, giving you an opportunity to address code violations A process to legalize your unpermitted ADU pursuant to CA state law AB 2533