ADU rules in San Bernardino County

Detached ADUs are allowed across the unincorporated county wherever a home is allowed: the land use tables list 'Accessory dwelling unit' as A (allowed use, no planning permit required) in the RL, RS and RM residential districts, the RC and AG resource and agriculture districts, CR (Rural Commercial) and SD-RES, always accessory to a residential use on the same site, and not at all in FW, OS or the other commercial and industrial districts. Chapter 84.36, added by Ord. 4504 (adopted January 13, 2026, effective February 12, 2026), defines a detached unit as one physically separated from the primary dwelling (a detached ADU larger than the existing home is deemed the primary dwelling), and Table 84-0 allows up to two ADUs of any type on a single-family lot, three on lots of five acres or more, with 4-foot side and rear setbacks and a 5-foot separation from other buildings. Separately, 84.36.080(b)(2) approves by right one new detached ADU of up to 800 sq ft of livable space with 4-foot side and rear setbacks, combinable with a JADU (Gov. Code 66323(a)(2)); multifamily lots may add up to eight detached ADUs (never more than the existing unit count) or two with a proposed multifamily building.

Attached and internal ADUs are allowed on the same lots: 84.36.040(a)(1) and (a)(3) authorize units attached to the side, top or below the primary dwelling and conversions of existing space in the home or an accessory structure (basement, attic, attached or detached garage, shed, storage area), including an old home converted to an ADU when a larger new primary dwelling is built (still capped at 1,200 sq ft). Attached units count toward the same two-ADU aggregate (three on five acres or more) and are capped at 50 percent of an existing primary dwelling and 1,200 sq ft, while conversions of existing space have no size cap and no setback or height requirement. 84.36.080(b)(1) approves by right one converted ADU and one JADU per lot within the proposed or existing space of the home or an accessory structure (up to 150 sq ft of expansion for ingress and egress), and on multifamily lots at least one ADU and up to 25 percent of the existing unit count may be built in non-livable space. A JADU (up to 500 sq ft of interior livable space, entirely within a single-family residence, one per lot) is allowed in the same districts as ADUs.

Table 84-0 in 84.36.070 caps attached and detached ADUs at 1,200 sq ft of livable space, and with an existing primary dwelling an attached ADU may not exceed 50 percent of that dwelling (note 7), but note 1 guarantees an ADU of up to 800 sq ft of livable space with 4-foot side and rear setbacks whatever the table's other limits. Conversions of existing space carry no maximum (a converted former primary dwelling stays capped at 1,200 sq ft under 84.36.040(a)(3)), JADUs are capped at 500 sq ft of interior livable space, and the minimums are 200 sq ft for ADUs and 150 sq ft for JADUs, never barring an efficiency unit. Heights are 18 feet for detached units plus 2 feet where the roof matches the primary dwelling's pitch and 25 feet for attached units, never more than two stories, with no height or setback limit for conversions built within existing dimensions. These limits meet or exceed the state floors of Gov. Code 66321(b) as amended by SB 543 (850 sq ft, or 1,000 sq ft with more than one bedroom, of interior livable space; 16-foot detached height) and match the 1,200 sq ft default of 66314(d)(5). HCD's September 18, 2026 findings letter on the county ordinance lists size among its topics and is not public; its roughly October 18, 2026 response deadline has passed with no amendment or readoption on the Board or Planning Commission record, so if the county also sent HCD no written response, Gov. Code 66326(d) voids Chapter 84.36 and the state standards apply instead (still a 1,200 sq ft detached cap and 50 percent of the home for attached units, but without the county's height and design rules; see caveats).

No for ADUs: 84.36.060(b) states that owner occupancy shall not be required for an accessory dwelling unit, as Gov. Code 66315 requires. For a JADU the owner must live in the main home or the JADU only when the JADU shares sanitation facilities with the main home; the requirement falls away when the JADU has its own bathroom or the owner is a governmental agency, land trust or housing organization, tracking Gov. Code 66333(b) as amended by AB 1154 effective January 1, 2026. Every JADU needs a deed restriction recorded with the County Recorder that bars separate sale and fixes the unit's size and attributes. Ord. 4504 narrowed the former 84.01.060(c)(2), which required JADU owner occupancy regardless of sanitation.

Table 84-0 requires one uncovered off-street space for each ADU on single-family and multifamily lots alike, which may be tandem on a driveway (note 12), and none for a JADU. Under 84.36.080(a)(3) the requirement does not apply to a JADU, to an ADU within one-half mile walking distance of public transit, in a historic district listed on the National or State Register or the county registry, within the proposed or existing primary dwelling or a converted accessory structure, where on-street permits are required but not offered to the occupant, within one block of a car-share vehicle, or when filed together with a new primary or multifamily dwelling on a lot meeting one of those tests; a garage, carport or covered parking structure removed or converted for an ADU never needs replacement. Gov. Code 66314(d)(10)(A) caps ADU parking at 'one parking space per accessory dwelling unit or per bedroom, whichever is less', so on a plain reading a studio ADU with no bedroom owes no space, while Table 84-0 asks one space of every unit; the December 18, 2025 staff report shows Ord. 4504 left the one-space rule unchanged, and HCD's September 18, 2026 findings letter on the ordinance lists parking among its topics. If the ordinance is void under Gov. Code 66326(d) for want of a timely response (unsettled; see caveats), only the state ceiling of one space per unit or per bedroom, whichever is less, with the 66322 exemptions, would apply. Table 84-0 does not expressly exempt the 800 sq ft by-right detached unit of 84.36.080(b)(2), but Gov. Code 66323(b) bars any standard that section does not authorize (it authorizes none on parking) and 84.36.080(b) approves those units notwithstanding anything to the contrary.

The land use tables list ADUs and JADUs as A, an allowed use needing no planning permit, in every district that allows them, and 84.36.050(a) says an ADU or JADU permit is considered and approved ministerially, without discretionary review or hearing, notwithstanding the need for a variance or special use permit. Land Use Services must decide completeness within 15 business days (15 more after a resubmittal) and approve or deny within 60 days of a complete application where a primary or multifamily dwelling exists, or within 30 days for a detached unit built from a county pre-approved plan; the 60 days may be delayed for a concurrent new-home application or at the applicant's written request (84.36.050(b), tracking Gov. Code 66317 as amended by SB 543). Before a permit issues the applicant needs written sewer availability or Environmental Health approval of a septic system (holding tanks are barred), water district or well approval, fire authority sign-off and county approval of drainage, ingress and egress (84.36.050(f)-(i)); units in the Floodplain Safety overlay must meet Chapter 82.14. The county posts pre-approved detached ADU plan sets on its Building and Safety handouts page.

84.36.060(a) lets an ADU or JADU be rented separately from the primary dwelling in all regions for terms longer than 30 consecutive days, and JADU rentals must always run longer than 30 days (Gov. Code 66333(g)). An ADU may be rented for 30 days or less only in the Mountain and Desert Regions, only with a short-term residential rental permit under Chapter 84.28 (listed as SUP, Special Use Permit, in the land use tables), and not if it was built under the 84.36.080(b) by-right exemptions, which state law holds to terms longer than 30 days (Gov. Code 66323(e)); Chapter 84.28 applies only in the Mountain and Desert Regions and the county's STR program says short-term rentals are only allowed there, so Valley Region ADUs are long-term only. STR permits are issued per dwelling unit, at most one per parcel under 2 acres and two on parcels of 2 acres or more, at most two per owner, are not transferable and carry transient occupancy tax, so on a parcel under 2 acres the house and the ADU cannot both be short-term rentals. Separate sale or conveyance of any ADU is prohibited except as authorized under what the ordinance prints as 'Section 66431' (a misprint for the Gov. Code 66341 qualified-nonprofit path); the county did not opt into a Gov. Code 66342 ADU-condominium ordinance, although a public comment at the December 18, 2025 Planning Commission hearing asked it to.