Everything homeowners ask about building an ADU in San Bernardino — answered with 2026 data.
Yes, ADUs are allowed in Most residential zones (R-1, R-2, R-3, multifamily) in San Bernardino, CA. The maximum size for a detached ADU is 1200 sq ft; reduces to 800 sq ft if lot coverage exceeded. Attached ADUs can be up to 1200 sq ft or 50% of primary dwelling, whichever is less. San Bernardino has an ADU-friendliness score of 8/10. Check our full San Bernardino ADU rules page for complete zoning details.
ADU construction in San Bernardino typically costs $160,000-$280,000. The cost per square foot averages $200-$260. Garage conversions are more affordable at $75,000-$140,000, while prefab ADUs cost $80,000-$150,000. Permit fees add $3,000-$12,000 estimated (building permit + plan check; varies by size) to your budget. See our detailed San Bernardino ADU cost guide.
Detached ADUs in San Bernardino can be up to 1200 sq ft; reduces to 800 sq ft if lot coverage exceeded. Attached ADUs are limited to 1200 sq ft or 50% of primary dwelling, whichever is less. Junior ADUs (JADUs) have a cap of 500 sq ft. Maximum height is 16 ft minimum; up to 25 ft with exceptions. You are allowed up to 1 ADU + 1 JADU per single-family lot; multifamily lots may add up to 8 detached ADUs (SB 1211), not exceeding the number of existing units, plus conversions of non-habitable space on a qualifying lot.
Rear setback: 4 ft minimum (detached new construction). Side setback: 4 ft minimum (interior side, detached new construction). Front setback: Base zone compliance. Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
No additional parking required (conversions/existing exempt). 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 under state law. 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 60 days mandatory for approval/denial of complete applications with an existing dwelling. Plan check: Included in the permit timeline; agency must respond within 60 days. Pre-approved plans availability: Yes - Pre-Selected ADU Plans Program: Morning Glory (462 sq ft, 1BR) and Carnation (738 sq ft, 2BR).
Average ADU rental income in San Bernardino: 1-bedroom units rent for $1,300-$1,700/month, 2-bedroom units for $1,700-$2,100/month. Short-term rentals: Subject to city/county ordinances; verify before planning. Expected ROI: 7-10 year payback.
The minimum lot size for an ADU in San Bernardino is No specific state minimum. 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-$140,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.