California ADU rules · San Bernardino County
Can I Build an ADU in Highland?
Yes — you can build an ADU in Highland. California's statewide ADU law requires every city, including Highland, 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
CA state law1 ADU + 1 JADU
At least one ADU and one JADU per single-family lot (a conversion ADU may also be possible).
Units on a multifamily lot
Local ruleconversions (>=1 or 25% of units) + up to 8 detached (not to exceed number of existing units); up to 2 detached on proposed multifamily
Limits detached ADUs on existing multifamily lots to 8 or the number of existing units, whichever is less; only 2 detached ADUs allowed on proposed multifamily lots.
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
Local maximum for detached ADUs with two or more bedrooms.
Max attached ADU size
Local rule50% of primary, >=850 (>=1,000 for 2+ bedrooms), max 1,200
Absolute maximum for attached ADUs is 1,200 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
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 ruleper base zone, but must allow 800 sq ft ADU with 4-ft side/rear setbacks if standard front setback would preclude it
Front setback can be reduced 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
Local ruleUp to 1 space
1 off-street space per ADU unless exempt; tandem and setback 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
Local ruleNot required
No replacement parking required for converted garages/carports.
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 ruleOnly for a JADU
Owner-occupancy required for JADUs only.
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, All other applicable construction permits
All applicable construction permits required in addition to building permit.
Highland-specific factors that can change the answer
State law sets the floor, but these local conditions often decide whether a specific parcel works.
Very High Fire Hazard Severity Zone (VHFHSZ)
ADUs are not allowed in high fire severity zones.
Historic resources
ADUs impacting historic resources must comply with Secretary of the Interior’s Standards.
Highland prohibits ADUs in high fire severity zones and limits detached ADUs on multifamily lots to 8 or the number of existing units. Attached and detached ADUs have a local maximum size of 1,200 sq ft.
Frequently asked questions
Can I build an ADU in Highland?
Yes. California's statewide ADU law requires Highland 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 Highland?
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 Highland?
Side and rear setbacks are limited to 4 ft. per base zone, but must allow 800 sq ft ADU with 4-ft side/rear setbacks if standard front setback would preclude it.
Is parking required for an ADU in Highland?
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 Highland?
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 Highland?
Owner-occupancy: only for a jadu. ADUs under 750 sq ft are also exempt from impact fees.
Sources
- Highland Municipal Code § 16.44.180, as amended by Ord. 471 § 2, 2025
- HMC § 16.44.180(E)(4)(a)-(e)
- HMC § 16.44.180(D)(2)(a)
- HMC § 16.44.180(D)(2)(c)
- HMC § 16.44.180(D)(5)
- HMC § 16.44.180(D)(5)(c)
- HMC § 16.44.180(E)(5)(h)
- HMC § 16.44.180(F)(2)
- HMC § 16.44.180(D)(1)
- HMC § 16.44.180(D)(2)(e)
- 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 § 66323 (by-right ADU/JADU, 800 sq ft, 4-ft setbacks)
- Cal. Gov. Code § 66333 (junior ADUs)
- Cal. Gov. Code § 66321 (size minimums & height)
- Cal. Gov. Code § 66322 (ADU parking; § 66334 covers JADU parking)
- 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 Highland'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 Highland Planning before relying on it.
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