Everything homeowners need to know about building an accessory dwelling unit in San Bernardino - size limits, setbacks, permits, and how California's statewide ADU law shapes what you can build here.
| ADU type | Max size | Max height | Notes |
|---|---|---|---|
| Detached, new construction (state-guaranteed floor) | 800 sq ft or smaller, with 4 ft side and rear setbacks | 16 ft | This size and setback combination must be approved ministerially no matter what other local standards say |
| Detached or attached (city standard pathway) | 850 sq ft for a studio/1-bedroom unit, 1,000 sq ft for 2+ bedrooms; attached units also capped at 50% of the primary home's floor area | 16-25 ft, depending on configuration | Never reduced below 800 sq ft by setback, lot coverage, or percentage limits |
| Junior ADU (JADU) | Up to 500 sq ft | Within the existing home | Created within the walls of the primary dwelling; requires a separate exterior entrance |
ADUs are permitted on any lot with a proposed or existing single-family or multifamily dwelling, citywide, per the Development Code's residential zone regulations. Confirm your parcel's zoning with the Planning Division before designing.
| Setbacks | 4 ft side and rear yard for both the guaranteed and standard pathways; a 25 ft front setback applies to standard-pathway units. No setback is required when converting an existing legal structure into an ADU. |
| Height | 16 ft for most detached ADUs; up to 18 ft (plus 2 ft for a matching roof pitch, for a 20 ft maximum) within a half-mile of a major transit stop; attached ADUs up to 25 ft or the underlying zone's height limit, whichever is lower, capped at two stories. |
| Parking | No additional off-street parking is required for the ADU itself. |
| Units per lot | Single-family lots can typically combine one JADU, one ADU converted from existing space, and one new detached ADU. Qualifying multifamily lots can add more (see below). |
| Owner-occupancy | Not required for ADUs. JADUs still require the property owner to live on site, in either the primary home or the JADU, unless the property is owned by a public agency, land trust, or housing organization. |
| Building code | Must meet current California Residential/Building Code dwelling unit standards. Fire sprinklers are only required in the ADU if they're also required in the primary home. |
| Rental restriction | No ADU or JADU may be rented for a term shorter than 30 days - short-term/Airbnb-style rentals aren't permitted. |
| Multifamily lots | Converted ADUs within existing multifamily buildings are allowed up to 25% of the existing unit count. Detached ADUs are capped at two on a lot with new multifamily construction, or up to eight on a lot with an existing multifamily dwelling (never exceeding the number of primary units). |
Worth knowing: published local reporting and city data on how many ADUs San Bernardino has actually permitted is thinner than what's available for larger California markets like Los Angeles or San Diego. That doesn't change what you're entitled to build - the statewide law guarantees a ministerial approval path regardless of how much local press coverage a city gets.
Call the Planning Division at (909) 998-2300 or email cityofsbplanning@sbcity.org to confirm your parcel's zoning and whether the 800 sq ft guaranteed pathway or the 850/1,000 sq ft standard pathway fits your project.
Pick one of the city's free pre-approved plans (Morning Glory, 462 sq ft, or Carnation, 738 sq ft, both from Tang Structural Engineers) or hire your own architect or designer.
Prepare a site plan, floor plans and elevations, and structural and energy calculations. Units of 501 sq ft or larger also need a school fee letter.
Initial reviews typically take 15-20 business days; corrected resubmittals are usually turned around in 10-15 business days. Reach Building & Safety at (909) 998-2000.
A deed restriction must be recorded with the County Recorder before your building permit is issued. Photovoltaic (solar) systems must be included in your original plan set - they can't be deferred to a later permit.
Construct your ADU and schedule the standard framing, plumbing, electrical, and final inspections before occupancy.
State law requires the city to approve or deny a complete ADU application within 60 days. Fees and timelines are approximate - confirm current figures with the Planning Division.
| Garage conversion | Roughly $60,000-$150,000, the least expensive path since the shell already exists |
| New detached ADU | Roughly $130,000-$280,000 for a code-compliant, freestanding unit, depending heavily on size and finishes |
| Pre-approved plan savings | Choosing the city's free Morning Glory or Carnation design can reduce design costs and shorten plan review compared to a fully custom project |
| Impact fees | Waived for ADUs and JADUs under 750 sq ft; larger units are charged proportionately to the primary dwelling's floor area under the Mitigation Fee Act |
| School fee letter | Required for units 501 sq ft or larger before permits are issued - budget the time to obtain it, even though the fee itself varies by district |
These are general ranges from local contractor estimates and regional reporting, not quotes - actual cost depends heavily on lot conditions, finishes, and site-specific factors like San Bernardino's higher wind, seismic, and fire-severity design requirements in some areas.
