Everything homeowners ask about building an ADU in San Bernardino — answered with 2026 data.
Yes, ADUs are allowed in All residential zones: ADUs are a permitted (P) use in the RE, RL, RS, RU, RM, RMH and RH zones and the RSH overlay (Table 04.01, 19.04.020). Under 19.04.030(2)(P)(6)(a) a Class 1 (state-law) ADU may be built on any lot in a residential or mixed-use zone that has a proposed or existing home, a Class 2 (locally regulated) ADU on any lot zoned for single-family or multifamily use, and a JADU only on a lot zoned for single-family residences in San Bernardino, CA. The maximum size for a detached ADU is 1,000 sq ft of interior livable space for a unit with two or more bedrooms and 850 sq ft for a studio or one-bedroom under the city's Class 2 standards (19.04.030(2)(P)(7)(a), Ordinance MC-1659); a Class 1 detached ADU under state law is 800 sq ft of livable space or less (5.a.ii). No lot-coverage, FAR, front-setback or open-space rule may force any ADU below 800 sq ft (7.a.iii). Minimum interior width 10 ft in every direction with a 7-ft ceiling (7.h.v). Attached ADUs can be up to 1,000 sq ft of interior livable space. San Bernardino has an ADU-friendliness score of 7/10. Check our full San Bernardino ADU rules page for complete zoning details.
ADU construction in San Bernardino typically costs $150,000-$300,000. The cost per square foot averages $180-$280. Garage conversions are more affordable at $75,000-$150,000, while prefab ADUs cost $180,000-$320,000. Permit fees add The posted Building & Safety fee schedule (07/2020) has no ADU line, so a new detached unit is priced like a new in-fill dwelling: plan review at the hourly rate of $122.37 (5 hours, about $612, for a new dwelling; 3 hours, about $367, for an addition), a building permit of $1,461 for a unit up to 1,200 sq ft (Table 1B, including electrical, plumbing and mechanical inspections) or $1.92 per sq ft for an attached unit with a bath or kitchen ($375 minimum, $1,459 maximum up to 1,200 sq ft), plus a 2% technology fee and 2% General Plan maintenance fee, a $55 zoning consistency review, $167.40 for the certificate of occupancy when it is on the building permit, state SMIP at 0.0001 x valuation and archive fees of $3.15 per plan sheet; expect roughly $2,300-$2,800 in city plan-check and permit fees for a detached ADU before school, sewer and impact fees. The Planning Division's February 2024 schedule lists no ADU review fee; MC-1659 lets the city set an ADU-permit processing fee by council resolution (4.b), so confirm with Planning. Pre-approved plans are bought from their designer at the designer's price to your budget. See our detailed San Bernardino ADU cost guide.
Detached ADUs in San Bernardino can be up to 1,000 sq ft of interior livable space for a unit with two or more bedrooms and 850 sq ft for a studio or one-bedroom under the city's Class 2 standards. Attached ADUs are limited to 1,000 sq ft of interior livable space. Junior ADUs (JADUs) have a cap of 500 sq ft of interior livable space, entirely inside the existing or proposed single-family house (an attached garage counts), with an efficiency kitchen and its own exterior entrance; it may share a bathroom with the house (19.04.030(2)(P)(3)(e)). One JADU per single-family lot, only on single-family-zoned land (6.a.iii). Maximum height is 16 ft for a detached ADU; 18 ft when the lot is within half a mile walking distance of a major transit stop or high-quality transit corridor (plus up to 2 ft, to 20 ft, to match the house's roof pitch) or on a multifamily lot with a multi-story building; an attached ADU may reach 25 ft or the zone's height limit, whichever is lower, and at most two stories. Height is measured from existing legal grade or the lowest floor, whichever is lower, to the peak (19.04.030(2)(P)(6)(b)). A Class 2 detached ADU is limited to one story (7.k). You are allowed up to Single-family lot: one conversion ADU on a qualifying lot.
Rear setback: 4 ft (19.04.030(2)(P)(5)(a)(ii) for a Class 1 detached ADU; 7.c.i for a Class 2 ADU). No setback beyond fire-code separation for a conversion inside existing space, and none when the ADU is built in the same location and to the same dimensions as an existing structure (7.c.ii). Side setback: 4 ft (same subsections). An existing multifamily building that already sits closer than 4 ft does not have to be altered to add a detached ADU (5.a.iv(a)). Front setback: 25 ft for a Class 2 ADU (19.04.030(2)(P)(7)(c)(i)), but the front setback may not be used to push the unit below 800 sq ft (7.a.iii); a Class 1 detached ADU of 800 sq ft or less is bound only by the 4-ft side and rear standard. None when rebuilding on an existing structure's footprint and dimensions (7.c.ii). Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
1 off-street space per Class 2 ADU (one per ADU or per bedroom, whichever is less), which may sit in a setback or as tandem parking in the driveway (19.04.030(2)(P)(7)(g)). No parking is required when the ADU is within half a mile walking distance of public transit (a bus stop or train station with fixed routes and set fares), is converted from the house or an accessory structure, is in a historic district, is within one block of a car-share stop, or where on-street permits are required but not offered to the ADU occupant; no parking is required for any Class 1 unit (a JADU, a conversion ADU or a detached ADU of 800 sq ft or less), and a garage or parking space removed for an ADU is not replaced (7.g.iii). Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.
Not required for an ADU (19.04.030(2)(P)(6)(g)(i)). A JADU requires an owner (a natural person holding title) to live in the house or the JADU unless the JADU has its own bathroom, or the property is owned by a government agency, land trust or housing organization (6.g.ii, matching AB 1154); a JADU also needs a recorded deed restriction before its certificate of occupancy (6.h). ADUs no longer need a deed restriction under MC-1659. Note that owner-occupancy rules vary by state law — California and several other states have eliminated this requirement for standard ADUs.
The ADU permit review timeline in San Bernardino is typically 15 business days for the city to tell you in writing whether the application is complete (and what is missing), the same 15 business days for each resubmittal, then 60 days from a complete application to approve or deny or the ADU is deemed approved; the clock pauses only if you ask for a delay or the ADU is filed with a new house (19.04.030(2)(P)(4)(c), SB 543). Building & Safety says a first plan-check round takes 15-20 business days and each later round 10-15 business days, with status on the online permit portal. Plan check: Plan review is paid at submittal at $122.37 per hour (5 hours for a new dwelling, 3 for an addition) and is done in-house; expedited review goes to an outside vendor at the vendor's rate. The city quotes 15-20 business days for the first round and 10-15 for each later round, inside the 60-day statutory decision window. Plans must follow the 2025 California building codes in force since January 1, 2026, and fire sprinklers are required only if the main house has them (19.04.030(2)(P)(6)(c)). Pre-approved plans availability: Yes, 2 plans in the Pre-Selected ADU Plans Program: a 462 sq ft one-bedroom, one-bath detached unit and a 738 sq ft two-bedroom, two-bath detached unit, both drawn by a private structural engineering firm and purchased from the designer (the city holds no rights to them). They still go through Planning pre-approval, a hold-harmless agreement and Building & Safety plan check, and may not fit every lot or site condition; both are at or below 750 sq ft, so neither owes city impact fees, and the 738 sq ft plan owes school fees.
Average ADU rental income in San Bernardino: 1-bedroom units rent for $1,550-$1,800/month, 2-bedroom units for $1,900-$2,200/month. Short-term rentals: No. An ADU or JADU may not be rented for less than 30 days, whenever it was built (19.04.030(2)(P)(6)(d); Gov. Code 66333(g) for JADUs under AB 1154). Expected ROI: 6-17% gross rental yield on a $150,000-$300,000 new detached ADU renting at $1,550-$2,200/mo; 12-35% gross on a $75,000-$150,000 garage conversion (before taxes, vacancy and financing).
The minimum lot size for an ADU in San Bernardino is None. An ADU needs only a lot in an eligible zone with a proposed or existing primary dwelling (19.04.030(2)(P)(3)(a)); a Class 2 ADU may not push total lot coverage above 50%, floor-area ratio above 45% or open space below 50%, except that none of those limits can reduce the ADU below 800 sq ft (7.a.iii, 7.b, 7.d, 7.e). This applies to detached ADUs — garage conversions and JADUs may have different or no lot size requirements.
Garage conversions are one of the most popular and affordable ADU options. In San Bernardino, a garage conversion typically costs $75,000-$150,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.
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