California ADU rules · Los Angeles County
Can I Build an ADU in Monrovia?
Yes — you can build an ADU in Monrovia. California's statewide ADU law requires every city, including Monrovia, 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 detached ADU (up to 800 sqft by-right) + 1 JADU (up to 500 sqft, within primary dwelling)
Detached ADU limited to 800 sqft by-right; JADU must be within the main house.
Units on a multifamily lot
Local ruleconversions (>=1 or 25% of units) + up to 2 detached
Only 2 detached ADUs allowed per multifamily lot, less than state default of 4-8.
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
CA state law1,200 sq ft
Statewide default cap for detached new-construction ADUs in the absence of a compliant local ADU ordinance. The unconditional by-right floor a city must always allow is 800 sq ft (see Guaranteed minimum size); a city with a compliant ordinance may set its own ceiling.
Max attached ADU size
Local rule50% of primary dwelling, >=220 sqft (state override: >=850/1,000 sqft if 2+ bedrooms)
Local rule is 50% of primary, but state override applies if it would restrict below 850/1,000 sqft.
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 rule16 ft
16 ft max for new detached or attached ADUs; state override applies for transit/multistory contexts.
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
Local ruleNo new ADU between primary dwelling and street, unless needed to allow an 800 sqft, 16' tall ADU with 4' setbacks
Front setback may be reduced only to guarantee one 800 sqft ADU.
Separation from main house
CA state lawNone required
No statewide separation requirement between the ADU and the primary dwelling.
Parking
Parking required
Local ruleNone
No additional parking required for any ADU or JADU.
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
Local ruleNot required
No replacement parking required when converting/demolishing garage/carport.
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
CA state lawOnly for a JADU
No owner-occupancy requirement for ADUs (the prior sunset was removed). A JADU may require owner-occupancy, principally where it shares sanitation with the main house.
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
CA state lawBuilding permit
Only a ministerial building permit — no conditional use permit or discretionary design review for a qualifying ADU.
Monrovia limits by-right detached ADUs to 800 sqft and allows only 2 detached ADUs on multifamily lots. No additional parking is required for ADUs or JADUs, and no replacement parking is needed when converting a garage.
Frequently asked questions
Can I build an ADU in Monrovia?
Yes. California's statewide ADU law requires Monrovia 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 Monrovia?
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 Monrovia?
Side and rear setbacks are limited to 4 ft. No new ADU between primary dwelling and street, unless needed to allow an 800 sqft, 16' tall ADU with 4' setbacks.
Is parking required for an ADU in Monrovia?
None. 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 Monrovia?
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 Monrovia?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Monrovia Municipal Code § 17.44.005 (ADUs/JADUs)
- Monrovia Municipal Code § 17.44.005(D)(1)(c), (B)(3)
- Monrovia Municipal Code § 17.44.005(D)(4)
- Monrovia Municipal Code § 17.44.005(D)(2)(a)
- Monrovia Municipal Code § 17.44.005(D)(1)(c), (D)(2)(c)
- Monrovia Municipal Code § 17.44.005(D)(2)(b)
- Monrovia Municipal Code § 17.44.005(D)(1)(c)3, (D)(4)(a)1, (B)(3)(f)
- Monrovia Municipal Code § 17.44.005(D)(1)(b)
- 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 § 66315 (owner-occupancy)
- 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 Monrovia'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 Monrovia Planning before relying on it.
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