How Much Does an ADU Cost in San Bernardino, CA?

Construction Cost Breakdown

Building an ADU in San Bernardino costs between $150,000-$300,000 for new construction, with per-square-foot costs averaging $180-$280. These figures include design, permitting, site preparation, and construction. The most affordable option is a garage conversion at $75,000-$150,000, while prefab/modular ADUs fall in between at $180,000-$320,000.

Permit Costs & Timeline

Permit fees in San Bernardino are 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. The review timeline is 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, with 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)). Impact fees are None for a JADU or for an ADU of 750 sq ft or less of interior livable space (Gov. Code 66311.5(c)(1) as amended by SB 543; MC-1659 8.a words the city's version as 'less than 750 sq ft', and the state boundary controls). Above 750 sq ft the fee is prorated: ADU floor area divided by the main house's floor area, times the full single-family fee (8.a.iii). The city's posted Land Development impact-fee schedule (effective February 15, 2022, indexed to the ENR index every July 15, so ask for current figures) totals about $17,300 per detached dwelling: local circulation $232.94, regional circulation $2,435, storm drain $3,925.91, law enforcement $639.07, library $637.89, aquatic $326.11, public meeting facilities $1,089.54 and parkland $8,044.32, so an 800 sq ft ADU behind a 1,600 sq ft house would owe about half of that. School fees are separate: San Bernardino City USD charges $5.38 per sq ft (effective August 3, 2026) on an ADU over 500 sq ft and nothing at 500 sq ft or less (66311.5(c)(3)); Rialto and Redlands USD set their own rates and the city asks for a school-fee letter at 501 sq ft and up. Sewer: SBMWD Rule 25 lists a $180 application fee, a $3,500 residential treatment capacity charge per dwelling unit and $420 per bedroom for collection capacity; a conversion ADU or JADU inside existing space owes no new connection or capacity charge (8.b.ii, 66311.5(d)), and a new detached unit may be charged only in proportion to its burden by floor area or fixture units (8.b.iii, 66311.5(e)). Addresses in the East Valley Water District pay that district instead. Pre-approved plans: 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.

Rental Income & ROI

A typical ADU in San Bernardino generates approximately $20,100 per year in rental income based on average 1-bedroom rents. At an average construction cost of $225,000, the estimated payback period is 11.2 years — before accounting for the resale value the ADU adds, which an appraiser determines from comparable sales in San Bernardino and varies by market (often less than build cost).

Ways to Reduce ADU Costs in San Bernardino