California ADU rules · Santa Clara County
Can I Build an ADU in Morgan Hill?
Yes — you can build an ADU in Morgan Hill. California's statewide ADU law requires every city, including Morgan Hill, 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 + 1 attached ADU + 1 JADU
Allows both 1 detached and 1 attached ADU plus 1 JADU on a single-family lot.
Units on a multifamily lot
Local ruleProposed multifamily: up to 2 detached ADUs per lot. Existing multifamily: up to 8 detached ADUs per lot (not to exceed number of existing units), plus at least 1 or up to 25% of existing units as conversion ADUs.
Detached ADU cap is 2 for proposed multifamily, up to 8 for existing multifamily.
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 ruleSame as detached by zone; if within front setback, max 800 sq ft
Attached ADU max size mirrors detached by zone, except 800 sq ft if in front setback.
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
CA state law16 ft
16 ft baseline; cities must allow 18 ft within ½ mi of a major transit stop or where the primary dwelling is two-story, and 20 ft on a lot with a multistory multifamily building.
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 ruleMust comply with zoning district front setback, except if not possible to build 800 sq ft ADU, then may be allowed in front setback (with intersection sight distance compliance)
Front setback may be relaxed if needed to accommodate an 800 sq ft ADU.
Separation from main house
CA state lawNone required
No statewide separation requirement between the ADU and the primary dwelling.
Parking
Parking required
CA state lawUp to 1 space
At most 1 space per ADU (or per bedroom, whichever is less) — and waived in the common cases below.
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
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
Local ruleBuilding permit, Demolition permit (for garage conversion, issued concurrently)
Demolition permit required for garage conversion, issued with building permit.
Morgan Hill allows both a detached and an attached ADU plus a JADU on single-family lots, with local maximum ADU sizes varying by zone. Attached ADUs may be up to 25 ft tall, and detached ADU height and size limits depend on zone and proximity to transit.
Frequently asked questions
Can I build an ADU in Morgan Hill?
Yes. California's statewide ADU law requires Morgan Hill 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 Morgan Hill?
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 Morgan Hill?
Side and rear setbacks are limited to 4 ft. Must comply with zoning district front setback, except if not possible to build 800 sq ft ADU, then may be allowed in front setback (with intersection sight distance compliance).
Is parking required for an ADU in Morgan Hill?
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 Morgan Hill?
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 Morgan Hill?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Morgan Hill Municipal Code Chapter 18.84 — Accessory Dwelling Units (Ord. No. 2341 N.S., § 9, 2-15-2023)
- MHMC § 18.84.050(B)(1)
- MHMC § 18.84.050(B)(2)-(3)
- MHMC § 18.84.050(D)(1), (D)(5)
- MHMC § 18.84.050(E)
- MHMC § 18.84.020(C)
- 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 § 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 Morgan Hill'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 Morgan Hill Planning before relying on it.
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