California ADU rules · Los Angeles County
Can I Build an ADU in Rosemead?
Yes — you can build an ADU in Rosemead. California's statewide ADU law requires every city, including Rosemead, to approve a qualifying accessory dwelling unit by right, plus a junior ADU (JADU) on a single-family lot. What varies city to city are the local specifics below.
Can you build one?
ADUs allowed
CA state lawYes — by right
ADUs and JADUs are allowed by right in all residential and mixed-use zones; ministerial approval, no hearing.
Units on a single-family lot
Local rule1 attached OR 1 detached + 1 JADU
Allows either 1 attached ADU, or 1 detached ADU plus 1 JADU on a single-family lot.
Units on a multifamily lot
Local ruleup to 2 detached + conversions (>=1 or 25% of units)
Limits detached ADUs on multifamily lots to 2; allows at least 1 attached ADU or up to 25% of units as conversions.
Junior ADU (JADU)
CA state lawAllowed
Up to 500 sq ft, within the walls of an existing single-family home (single-family lots only).
Size & height
Max detached ADU size
Local rule1,200 sq ft
1,200 sq ft max for detached ADU with more than one bedroom; if both a JADU and detached ADU are built, detached ADU is limited to 800 sq ft.
Max attached ADU size
Local rule50% of primary; if primary <1,600 sq ft, then 800 sq ft allowed
Attached ADU limited to 50% of primary residence; 800 sq ft minimum if primary residence is less than 1,600 sq ft.
Guaranteed minimum size
CA state law800 sq ft
An 800 sq ft ADU must be allowed regardless of FAR/lot-coverage caps; a city also cannot cap an attached ADU below 850 sq ft (1,000 for 2+ bedrooms).
Max JADU size
CA state law500 sq ft
Max height
Local rule17 ft
One-story detached ADU: 17 ft; two-story: 30 ft; if primary residence is less than 16 ft, ADU max height is 16 ft.
Setbacks
Side setback
CA state law4 ft
A city cannot require more than 4 ft side or rear setback; conversions of existing structures are exempt.
Rear setback
CA state law4 ft
Front setback
CA state lawNo front setback may block the mandatory 800 sq ft / 16-ft / 4-ft-setback ADU; otherwise per base zone
Separation from main house
Local rule10 ft
10 ft minimum separation required between detached ADU and primary dwelling, unless not feasible (then state minimums apply).
Parking
Parking required
Local ruleUp to 1 space
One parking space per bedroom or per ADU, whichever is less; tandem parking allowed.
Transit parking exemption
CA state lawYes — no parking required near transit & for conversions
No parking may be required within ½ mi walking distance of transit, in a historic district, for an ADU within an existing structure, within one block of car-share, or in certain permit-parking areas.
Garage-conversion replacement parking
CA state lawNot required
When a garage/carport is demolished or converted to build an ADU, replacement parking cannot be required.
Approval, timeline & cost
Approval path
CA state lawMinisterial (by right)
No public hearing or discretionary design review for a qualifying ADU.
Approval timeline
CA state law60 days
The agency must act within 60 days of a complete application — and the ADU is deemed approved if it does not.
Owner-occupancy
Local ruleNot required
No owner-occupancy required for ADUs permitted between Jan 1, 2020 and Jan 1, 2025.
Impact-fee waiver
CA state lawWaived under 750 sq ft
An ADU of 750 sq ft or less pays no impact fees (the 750 sq ft threshold itself is exempt under § 66311.5); larger ADUs pay fees proportional to the primary dwelling. JADUs (≤ 500 sq ft) are exempt.
Permits required
Local ruleBuilding permit, Administrative site plan/design review
Both building permit and administrative site plan/design review required.
Rosemead-specific factors that can change the answer
State law sets the floor, but these local conditions often decide whether a specific parcel works.
Historic Districts
No ADU parking required in historic districts; conversions may have additional review.
Rosemead limits detached ADUs on multifamily lots to two and requires a 10-foot separation from the primary dwelling for detached ADUs. Owner-occupancy is not required for ADUs permitted through 2024.
Frequently asked questions
Can I build an ADU in Rosemead?
Yes. California's statewide ADU law requires Rosemead to approve a qualifying accessory dwelling unit ministerial (by right), plus a junior ADU (JADU) on a single-family lot.
How big can an ADU be in Rosemead?
A detached ADU of at least 1,200 sq ft must be allowed, and an ADU of 800 sq ft can never be zoned out by floor-area or lot-coverage limits. A JADU can be up to 500 sq ft.
What are the setback requirements for an ADU in Rosemead?
Side and rear setbacks are limited to 4 ft. No front setback may block the mandatory 800 sq ft / 16-ft / 4-ft-setback ADU; otherwise per base zone.
Is parking required for an ADU in Rosemead?
Up to 1 space. No parking can be required within ½ mile of transit, for conversions, or for units inside the primary home. When a garage is converted, replacement parking is not required.
How long does ADU approval take in Rosemead?
A complete application must be acted on within 60 days, with ministerial (by right) — no public hearing or discretionary design review for a qualifying ADU.
Do I have to live on the property to build an ADU in Rosemead?
Owner-occupancy: not required. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Rosemead Zoning Code §17.30.190; Table 17.30.190.1; Ord. No. 931, § 5(Exh. A), 10-22-13
- Rosemead Zoning Code §17.30.190.C.3
- Rosemead Zoning Code §17.30.190.C.4–5
- Rosemead Zoning Code Table 17.30.190.1
- Rosemead Zoning Code §17.30.190.C.10; State Gov. Code §66317
- Rosemead Zoning Code §17.30.190.C.1
- Rosemead Zoning Code Table 17.30.190.1; §17.30.190.C.12
- Cal. Gov. Code §§ 66310–66342 (ADU Law)
- HCD 2025 Accessory Dwelling Unit Handbook
- Cal. Gov. Code § 66317 (ministerial approval, 60-day deadline)
- Cal. Gov. Code § 66333 (junior ADUs)
- Cal. Gov. Code § 66321 (size minimums & height)
- Cal. Gov. Code § 66323 (by-right ADU/JADU, 800 sq ft, 4-ft setbacks)
- Cal. Gov. Code § 66322 (ADU parking; § 66334 covers JADU parking)
- Cal. Gov. Code § 66314 (local ordinance standards)
- Cal. Gov. Code § 66311.5 (impact fees: none for an ADU ≤ 750 sq ft or JADU ≤ 500 sq ft)
Last updated 2026-06-25. This is an AI-assisted summary of Rosemead's ADU rules, drawn from its published ordinance and California ADU law — general information, not legal advice, and it may be incomplete or out of date. Verify the controlling rule for your specific parcel with Rosemead Planning before relying on it.
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