How big can an attached ADU be in Long Beach?
As of October 2026, the City of Long Beach allows an attached addition ADU on a single-family lot of up to 50% of the main home's floor area or 800 sq ft, whichever is more. So a 1,200 sq ft house can still add an 800 sq ft attached unit. If you convert part of the existing house instead of adding on, the city sets no size limit.
How tall can it be?
As of October 2026, an attached ADU on a single-family lot can be 25 feet and two stories, or the zoning district's limit, whichever is less. That makes a second-story ADU over part of the house possible in some districts.
What must an attached ADU include?
- An independent exterior entrance.
- No interior door connecting it to the main home.
- A full bathroom.
- A full kitchen with a permanent cooking appliance.
These are Long Beach's minimum ADU features as of October 2026. If you want an interior door to the main house, a junior ADU is the type that allows it.
What setbacks apply to an attached addition?
New construction follows the same 4-foot interior side and rear setbacks as a detached ADU, with the rear measured to the alley centerline on alley lots. Front and street-side setbacks follow your zoning district. Rules as of October 2026.
What design issues come up with attached units?
Sharing a wall means sharing sound. HCD guidance recommends a sound barrier in walls between an ADU and the main house. We also plan where the new roof meets the old one, how the entrance stays private, and whether your electrical panel can carry a second kitchen.
Attached ADU or backyard cottage?
It depends on your lot. Attached units can work on lots where the rear yard is too small for a detached building, and they can share some structure with the house. A backyard cottage gives more separation. If your house is listed or in a historic district, design review can affect either choice, so we check that first.
Related
Rules as of October 2026, from the City of Long Beach ADU bulletin (IB-PZ-001) and zoning summary, and HCD guidance.
See what fits on your lot
Send your address. We check your zoning height limit, setbacks and floor area, then tell you how large an attached unit can be.