San Bernardino County
Rancho Cucamonga ADU rules
Research summary of local ADU rules on file for Rancho Cucamonga in San Bernardino County. Not a determination for a specific lot.
City or county ADU page
Check any California address for freeRancho Cucamonga rules on file
Local rules recorded in this project for this jurisdiction. Where a city figure on file is stricter than the state baseline on file, both are shown.
Which rules apply
Rancho Cucamonga's ADU rules are in Development Code Chapter 17.100, restated by Ordinance 1049. Three items are left out of this summary because they may conflict with state law; state rules apply to those items.
Source: Rancho Cucamonga Municipal Code Chapter 17.100 Accessory Dwelling Units and Junior Accessory Dwelling Units (eCode360; Ord. 1049), Ch. 17.100 (Purpose; Ord. 1049), accessed 2026-10-25.
Review and timing
ADUs and junior ADUs need a building permit and are “approved” or denied within 60 days of a complete application, without discretionary review or a hearing. “Pre-approved” detached ADU plans from the City's website are decided within 30 days. No minor exceptions to the chapter are granted.
Source: Rancho Cucamonga Municipal Code Chapter 17.100 Accessory Dwelling Units and Junior Accessory Dwelling Units (eCode360; Ord. 1049), Ch. 17.100 (Permit requirements), accessed 2026-10-25.
How many units (state categories)
Single-family lots: one ADU and one junior ADU inside the existing or proposed home or an existing accessory structure (plus 150 sq ft for entry), combined with one new detached ADU of up to 800 sq ft with 4 ft side and rear setbacks. Multifamily: conversions of non-living space up to 25% of the units (at least one), and up to eight detached ADUs with an existing building (not more than the existing units) or two with a proposed one.
Source: Rancho Cucamonga Municipal Code Chapter 17.100 Accessory Dwelling Units and Junior Accessory Dwelling Units (eCode360; Ord. 1049), Ch. 17.100 (Categories 1-4, Gov. Code 66323), accessed 2026-10-25.
Extra ADU on large lots
Lots of at least 20,000 sq ft with a single-family home may have one additional attached, detached or conversion ADU, reviewed ministerially under the ADU development standards.
Source: Rancho Cucamonga Municipal Code Chapter 17.100 Accessory Dwelling Units and Junior Accessory Dwelling Units (eCode360; Ord. 1049), Ch. 17.100 (Additional ADUs), accessed 2026-10-25.
Size and height (other ADUs)
Detached ADUs up to 1,200 sq ft; 16 ft tall, 18 ft within a half mile of a major transit stop or high-quality transit corridor (20 ft to match the main home's roof pitch) or on a lot with a multistory multifamily building. Attached ADUs up to 25 ft; ADUs over a garage follow the zone's height limit.
Source: Rancho Cucamonga Municipal Code Chapter 17.100 Accessory Dwelling Units and Junior Accessory Dwelling Units (eCode360; Ord. 1049), Table 17.100.050-1, accessed 2026-10-25.
Setbacks and lot coverage
4 ft from side and rear lines; the zone's front setback and lot coverage apply unless they would block an 800 sq ft, 16 ft ADU with 4 ft side and rear setbacks. No setback for an ADU in an existing structure or rebuilt in the same place and size.
Source: Rancho Cucamonga Municipal Code Chapter 17.100 Accessory Dwelling Units and Junior Accessory Dwelling Units (eCode360; Ord. 1049), Ch. 17.100 (Lot Coverage; Setbacks), accessed 2026-10-25.
Parking
New detached ADUs need one space (tandem, garage or setback areas allowed), using the main home's driveway unless there is an alley or corner-lot access. None within a half mile walk of public transit, in a historic district, for ADUs in the home or an existing accessory structure, where on-street permits are not offered, within one block of a car share station, or when applied for with a new home. Converted or demolished garages need not be replaced.
Source: Rancho Cucamonga Municipal Code Chapter 17.100 Accessory Dwelling Units and Junior Accessory Dwelling Units (eCode360; Ord. 1049), Ch. 17.100 (Parking), accessed 2026-10-25.
Entrance and utilities
Each ADU has its own entrance, kitchen and bathroom, and may have separate meters. Sprinklers are not required unless the main home needs them.
Source: Rancho Cucamonga Municipal Code Chapter 17.100 Accessory Dwelling Units and Junior Accessory Dwelling Units (eCode360; Ord. 1049), Ch. 17.100 (Facilities; Utility Services; Fire Sprinklers), accessed 2026-10-25.
Design near the street
ADUs in the front yard, next to the main home or visible from the street: roof and wall color, material and texture substantially the same as the main home, no visible exterior stairs above the first floor, and driveways and walkways on no more than 50% of the front yard. Mills Act properties follow Mills Act guidelines.
Source: Rancho Cucamonga Municipal Code Chapter 17.100 Accessory Dwelling Units and Junior Accessory Dwelling Units (eCode360; Ord. 1049), Ch. 17.100 (Design standards), accessed 2026-10-25.
Junior ADUs
Up to 500 sq ft inside the walls of the existing or proposed home (attached garages count), with its own exterior entry and an efficiency kitchen; it may share a bathroom with the home through an interior entry. No extra parking.
Source: Rancho Cucamonga Municipal Code Chapter 17.100 Accessory Dwelling Units and Junior Accessory Dwelling Units (eCode360; Ord. 1049), Sec. 17.100.070, accessed 2026-10-25.
Rentals and separate sale
Rentals must be for more than 30 days. An ADU may not be sold separately except under the nonprofit tenancy-in-common rules of Gov. Code 66341, or as a condominium.
Source: Rancho Cucamonga Municipal Code Chapter 17.100 Accessory Dwelling Units and Junior Accessory Dwelling Units (eCode360; Ord. 1049), Ch. 17.100 (Sales and Separate Conveyance; Rental Terms), accessed 2026-10-25.
Older unpermitted units
The City will not deny a permit for an unpermitted ADU or junior ADU built before 2020 for building-standard or ADU-law violations unless a correction is needed under Health and Safety Code 17920.3, and does not charge impact or connection fees except as state law allows.
Source: Rancho Cucamonga Municipal Code Chapter 17.100 Accessory Dwelling Units and Junior Accessory Dwelling Units (eCode360; Ord. 1049), Ch. 17.100 (Unpermitted ADUs and JADUs), accessed 2026-10-25.
Where to ask
Rancho Cucamonga Planning and Building and Safety. The City's ADU handbook (May 2024) predates Ordinance 1049; the code controls.
Source: City of Rancho Cucamonga ADU Handbook (updated May 21, 2024), accessed 2026-10-25.
California state rules on file
The statewide baseline recorded from state law and the HCD ADU Handbook.
Detached size cap described in state law
1,200 sq ft. Recorded in this rules file from Government Code section 66314.
Source: California Government Code section 66314, 66314, accessed 2026-10-16.
Side and rear setback cap for a new ADU
4 ft. Recorded in this rules file from Government Code section 66314, which describes a cap on side and rear setbacks for a new ADU.
Source: California Government Code section 66314, 66314, accessed 2026-10-16.
Setback for a conversion of an existing structure
No additional setback, as recorded in this rules file from Government Code section 66314 for a conversion of an existing structure.
Source: California Government Code section 66314, 66314, accessed 2026-10-16.
Minimum lot size
A city may not impose a minimum lot size for an ADU, as recorded in this rules file from Government Code section 66314.
Source: California Government Code section 66314, 66314, accessed 2026-10-16.
Minimum unit the handbook says cities must allow
At least an 800 sq ft ADU with 4 ft side and rear setbacks. The HCD ADU Handbook (updated March 2026) describes this under section 66321(b)(3).
Source: HCD ADU Handbook, 66321(b)(3); handbook updated March 2026, accessed 2026-10-16.
Detached height described in the handbook
16 ft, or 18 ft or 20 ft in some cases. The HCD ADU Handbook (updated March 2026) describes this under section 66321(b)(4).
Source: HCD ADU Handbook, 66321(b)(4); handbook updated March 2026, accessed 2026-10-16.
Permit decision deadline
60 days. Recorded in this rules file from Government Code section 66317(a)(3): the permitting agency must decide on (approve or deny) a completed ADU application within 60 days when an existing single-family or multifamily dwelling is on the lot. Section 66317(a)(1) says the application is considered ministerially, without discretionary review or a hearing.
Source: California Government Code section 66317, 66317(a)(1), (a)(3), accessed 2026-10-17.
Owner-occupancy requirement
None. Recorded in this rules file from Government Code section 66315: a local agency may not impose an owner-occupancy requirement on an ADU. It may require that the property be used for rentals of terms 30 days or longer. The HCD ADU Handbook (updated March 2026) describes the same rule.
Source: California Government Code section 66315, 66315; HCD ADU Handbook updated March 2026, accessed 2026-10-17.
Parking near public transit
No parking standards within one-half mile walking distance of public transit. Recorded in this rules file from Government Code section 66322(a)(1). Section 66322(a) lists several other cases where parking standards may not be imposed.
Source: California Government Code section 66322, 66322(a), accessed 2026-10-17.
Ministerial categories
The HCD ADU Handbook (updated March 2026) states that Government Code section 66323 sets four ministerial categories. This rules file does not restate those four categories.
Source: HCD ADU Handbook, 66323; handbook updated March 2026, accessed 2026-10-16.
Fire Hazard Severity Zones
If your lot is in a Fire Hazard Severity Zone, the CAL FIRE Office of the State Fire Marshal says in Information Bulletin 25-004 (issued March 3, 2025): “Fire Hazard Severity Zones (FHSZs) should not restrict the development of Accessory Dwelling Units (ADUs). However, additional building standards may be necessary, including but not limited to California Fire Code Chapter 49 and California Building Code Chapter 7A.” State ADU law does not itself bar an ADU there. A city or county may still apply its building code, including wildfire-resistant construction (Gov. Code 66314(d)(8)); require side and rear setbacks “sufficient for fire and safety” for a unit converted under 66323(a)(1); and decline parking in setbacks on specific fire and life safety findings (66314(d)(10)(B)). It may also consider public safety when it designates where ADUs may be permitted (66314(a)). Sprinklers can't be required in an ADU or JADU if the primary residence doesn't need them (66314(d)(12), 66323(d)). Some cities and counties still apply their own fire-zone limits. Where this summary has one, it is listed with the local rules. This summary does not look up your lot. Check the CAL FIRE Fire Hazard Severity Zone map viewer linked from the State Fire Marshal's Fire Hazard Severity Zones page: https://experience.arcgis.com/experience/5065c998b4b0462f9ec3c6c226c610a9
Source: CAL FIRE Office of the State Fire Marshal Information Bulletin 25-004, page 4, issued March 3, 2025; Gov. Code 66314, 66323, accessed 2026-10-20.
State baseline on the directory → · State ADU rules on the homepage →
Can I build an ADU in Rancho Cucamonga?
State law sets a baseline for ADUs in Rancho Cucamonga, and the local standards on file are listed on this page. Whether a specific lot can add an ADU depends on zoning, utilities, and other site facts this page does not measure. Confirm with the City of Rancho Cucamonga Planning and Building and Safety Departments, or run a free address summary.
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