Research by DoINeedAPermit Research Team · Updated May 2026
The Short Answer
California Government Code 65852.2 mandates that San Bernardino issue ADU permits for detached units, garage conversions, and junior ADUs regardless of local zoning — but the city still issues the permit and charges fees. All ADUs require building permits; nothing is exempt.
San Bernardino adopted an ADU ordinance in 2018 that aligns with state law, but the real game-changer is AB 881 (effective 2021), which stripped most local zoning objections off the table. San Bernardino can no longer deny an ADU on a single-family lot if you follow state-law minimums: the city must approve it within 60 days per AB 671. What makes San Bernardino different from its neighbors (Riverside, Ontario, Rialto) is how the city has implemented its permit fee schedule and online filing system. San Bernardino's building department processes ADU permits through its web portal with a flat plan-review fee plus impact fees; the city publishes fee schedules that are typically 10-15% lower than neighboring Riverside County jurisdictions for mid-size ADUs because San Bernardino doesn't impose a discretionary 'ADU overlay review.' However, if your lot is in a hillside fire zone (very common in the foothills near Lytle Creek or Crestline areas), or in the flood plain near the Santa Ana River, the city applies additional setback and utility requirements that can kill small-lot ADU feasibility — unlike coastal jurisdictions that face fewer topographic constraints. Bottom line: permit is non-negotiable, but the state has your back on zoning; costs and timeline depend heavily on your lot's hazard zone and utilities.

What happens if you skip the permit (and you needed one)

San Bernardino ADU permits — the key details

California Government Code 65852.2 is the foundation: it requires San Bernardino (and every other California city) to approve ADUs on single-family residential lots if they meet state minimums — owner-occupied or not, regardless of local zoning objection. The state law sets a floor, not a ceiling: minimum lot size (no minimum if owner-occupied; 2,500 sq ft if rental), maximum size (25% of main house or 1,200 sq ft, whichever is smaller; junior ADUs up to 500 sq ft), setback minimums (no setback required if inside existing footprint; 4 ft if detached), and parking (waived if within 1/2 mile of transit or in 'sensitive communities'). San Bernardino is classified as a sensitive community under CA law due to its median income, so parking waivers are standard here. The city's 2018 ADU ordinance (San Bernardino Municipal Code Title 19) adopted these minimums and added local criteria: detached ADUs on single-family lots get ministerial approval (no discretionary review), meaning the city's planning staff cannot say 'no' based on neighborhood objection or aesthetics — only on code compliance. This is radically different from non-ADU-friendly states or cities where discretionary approval still exists. AB 671 (2021) added a 60-calendar-day shot clock for ADU permit decisions; if San Bernardino doesn't issue or deny within 60 days, your permit is deemed approved. This has real teeth: many applicants in San Bernardino have historically seen their permits approved on day 60 when the city couldn't finish plan review in time.

Detached ADUs — the most common type in San Bernardino's hillside neighborhoods — must meet setback requirements from property lines and main dwelling. State law allows 4-foot setbacks for new detached ADUs, but San Bernardino's code also cross-references local setback ordinances for fire zones: in hillside fire areas (common north of I-215 toward the San Bernardino National Forest), the city may enforce 10-20 foot setbacks per the local fire code appendix. This is where many small-lot ADU projects fail in San Bernardino: a 40x80 foot lot with setback constraints may not have room for a 500 sq ft detached ADU. Garage conversions and ADUs-above-garages face fewer setback constraints because they are within the existing footprint. Foundation and flood requirements depend on lot location: most of San Bernardino's valley floor (near the Santa Ana River, from downtown west to Riverside County line) is in FEMA flood zone A or AE, meaning your ADU foundation must be elevated or floodproofed per IRC R322; design flood elevation is typically 5-8 feet above current grade in this zone. Mountain and foothill lots (northeast of the city, Crestline area) have soil expansion concerns — expansive clay is common in these areas — requiring soil testing and pier-and-beam or post-tension slab design per IRC R403.1.8. The city's building department requires a geotechnical report for any detached ADU on undeveloped slopes steeper than 15% (very common in hillside subdivisions).

Utility and sub-metering requirements often derail ADU projects because applicants underestimate the cost and timeline. California Government Code 65852.22 (the sub-meter law) requires that if the main dwelling and ADU share a water or sewer connection, the ADU must have its own sub-meter or the utility company must be willing to install a separate service. San Bernardino's water provider varies by zone: City of San Bernardino Water Department serves most of the city proper, but San Bernardino Valley Water District serves outer zones (Loma Linda area), and each has different sub-metering policies. City Water Department allows sub-metering at a cost of $2,000–$5,000 per meter plus monthly fees. Some ADU applicants discover mid-project that their lot cannot get a separate sewer connection due to septic-tank regulations (common in Crestline and mountain areas); this forces them to either abandon the ADU project or apply for a septic-system modification, adding 8-12 weeks and $5,000–$10,000 in cost. The building department requires sub-metering or separate-service letters from the utility during plan check; you cannot proceed to construction without this approval in your permit set.

Plan check and inspection timeline for San Bernardino ADUs typically runs 6-8 weeks for standard projects (detached ADU on compliant lot) and 10-14 weeks for hillside or flood-prone lots (due to geotechnical and fire-safety review). The city uses a concurrent review model for ADUs: planning staff and building staff review simultaneously, which saves time compared to sequential review in other jurisdictions. However, San Bernardino's building department has a backlog (common post-2021 when AB 881 opened the floodgates), so initial plan review may take 3-4 weeks. Once you submit, expect two rounds of comments: first round focuses on setbacks, parking, unit count, and state-law compliance; second round focuses on building code, utility sub-metering, and fire/flood mitigation. Each comment cycle takes 2-3 weeks. Inspections are the standard building set: foundation (if detached), framing (5-7 days after framing complete), rough trades (electrical, plumbing, mechanical), drywall, insulation, and final. Each inspection requires a 24-48 hour advance notice. The planning department also conducts a final inspection to verify the ADU matches the approved plans and is not exceeding unit count (one ADU per single-family lot is the state-law limit).

Permit fees and cost basis for San Bernardino ADUs run $4,000–$12,000 total, depending on unit size and location. The building permit fee is calculated as 1.5-2% of estimated construction valuation (similar to other trades), so a $300,000 detached ADU incurs a $4,500–$6,000 building permit. Impact fees (schools, parks, traffic) add another $2,000–$4,000 for single-family residential in San Bernardino. Plan-review fees are typically $1,500–$2,500 (flat or per-sheet pricing). If your lot requires geotechnical review (hillside) or flood mitigation plan, add another $1,000–$2,000. Owner-builder permits are allowed under California Business & Professions Code 7044 (owner can do the work themselves), but electrical and plumbing must be done by a licensed contractor or the owner must hold a Class C-10 (electrical) or C-36 (plumbing) license. Many San Bernardino applicants use licensed contractors for rough trades and do finishing work owner-builder; this saves $10,000–$20,000 on labor but doesn't reduce permit fees. The city's online portal (San Bernardino's PermitHub or equivalent) allows you to apply, upload plans, and track status; some applicants report that the portal is slower than paper filing, but it is the recommended method.

Three San Bernardino accessory dwelling unit (adu) scenarios

Scenario A
Detached 500 sq ft, single-story ADU on a compliant 8,000 sq ft lot in east San Bernardino (non-hillside, non-flood zone)
You own a flat residential lot in the Westmont or South Hills area, zoned R-1 (single-family), with a 1,500 sq ft main dwelling. You want to build a new 500 sq ft detached ADU (1 bed, 1 bath, separate kitchen, separate entrance, 6-foot setback from rear property line). The state law and San Bernardino code allow this: your lot is large enough (8,000 sq ft exceeds the no-minimum threshold), the ADU is within the 25% / 1,200 sq ft cap, and you are owner-occupied, so parking waiver applies. Your site is outside flood zones and has no slopes steeper than 15%, so no geotechnical report is required. The building department's plan check is straightforward: your ADU meets all setbacks, has compliant egress per IRC R310 (one window + one door minimum), utility sub-metering is feasible (the main sewer main is 40 feet away and can be tapped; water can be sub-metered for $3,000). Permit timeline is 6-8 weeks from submission to issuance. Permit fees: building permit $4,500 (1.5% of $300,000 estimated cost), impact fees $2,500, plan review $1,500, geotechnical $0 (waived). Total permit cost: $8,500. Construction cost estimate: $300,000–$350,000 (material and labor; owner-builder labor on finishing saves $20,000–$30,000). Inspections: foundation (week 2 of construction), framing (week 4), rough trades (week 6), drywall (week 8), final (week 10). No hold-ups expected; you can occupy 10-12 weeks after permit issuance if you fast-track construction.
Detached, new construction | 500 sq ft, 1 bed/1 bath | Owner-occupied (parking waived) | Separate kitchen + entrance | Separate sewer + water sub-meter required | Non-hillside lot, no flood zone | Building permit $4,500 + impact fees $2,500 + plan review $1,500 | Total permit: $8,500 | Timeline: 6-8 weeks permit, 10-12 weeks construction | Owner-builder allowed (contractor for electrical/plumbing)
Scenario B
Garage conversion ADU (700 sq ft) on a hillside lot in Crestline foothills with mandatory fire-zone setbacks
You own a 6,000 sq ft lot on a 20% slope in the Crestline/Lytle Creek fire-zone area (north of Highway 18, toward San Bernardino National Forest). Your main dwelling is a 1,800 sq ft cabin. Your detached two-car garage (24x24) is 12 feet from the main house and 8 feet from the rear property line. You want to convert the garage into a 700 sq ft ADU (2 bed, 1.5 bath, kitchen, separate entrance via new door on the side facing away from forest). State law allows this — garage conversions get ministerial approval and do not count against the single-family-lot ADU cap in some interpretations (though San Bernardino counts it as the lot's one ADU). The fire zone is the complication: San Bernardino's fire-safety overlay requires 10-15 foot setbacks from property lines in high-fire-hazard zones. Your rear setback (8 feet) is 2-7 feet short. However, because the structure exists (pre-existing nonconforming), the conversion itself is allowed; the city will issue the permit but may require fire-mitigation conditions: defensible space (clearing brush 30 feet from structure), Class A roof upgrade, and ember-resistant venting. A geotechnical report is required (your lot is >15% slope) — cost $2,500–$4,000, timeline 3-4 weeks. Utility situation: the existing garage shares the main house's sewer and water; sub-metering is required but feasible (adding $2,500–$4,000). Plan check timeline is 8-10 weeks due to fire review. Permit fees: building permit $3,500 (1.5% of $235,000 estimated cost for conversion; lower than new construction), impact fees $1,500, plan review $1,500, geotechnical report required $3,000. Total permit cost: $9,500. Fire-mitigation compliance adds another $5,000–$8,000 (defensible space work, roof upgrade). Construction cost: $200,000–$250,000 (conversion is cheaper than new because structure exists). Timeline: 8-10 weeks permit, 8-10 weeks construction. The fire-zone overlay delay is the main difference from Scenario A — without fire review, this project would be 6-7 weeks.
Garage conversion, existing structure | 700 sq ft, 2 bed/1.5 bath | Hillside lot (20% slope), fire-zone overlay | Defensible space + roof upgrade required | Geotechnical report mandatory | Sub-meter required (shared utilities) | Building permit $3,500 + impact fees $1,500 + plan review $1,500 + geotechnical $3,000 | Total permit: $9,500 | Fire-mitigation costs: $5,000–$8,000 additional | Timeline: 8-10 weeks permit, 8-10 weeks construction
Scenario C
Junior ADU (400 sq ft, within main-dwelling footprint) on a flood-prone lot near Santa Ana River with separate entrance
You own a 5,000 sq ft lot in south San Bernardino (near the Santa Ana River), zoned R-1. Your main dwelling is a 1,400 sq ft single-story ranch. The lot is in FEMA flood zone AE; flood elevation is 6.5 feet. You want to add a junior ADU (400 sq ft, 1 bed/1 bath, separate entrance from a new side door, shares main-dwelling kitchen with a pass-through to the new unit, no separate kitchen). This is a junior ADU under CA Government Code 65852.22, which means it is ministerial (no discretionary review) and counts as part of the main dwelling for most purposes (though San Bernardino still requires a building permit and issues a separate use-and-occupancy certificate). Because the junior ADU is within the existing footprint (you are converting 400 sq ft of den/office space and adding a separate entry), setback and parking are non-issues. Flood mitigation is the key requirement: because the lot is in flood zone AE, your junior ADU must be elevated or floodproofed to the base flood elevation (6.5 feet). This means one of two options: (1) raise the main dwelling and new ADU room 6.5 feet via new posts/piers (very expensive, $80,000+), or (2) floodproof to 6.5 feet per FEMA guidelines — install watertight doors, protect all utilities (HVAC, electrical, plumbing) above the BFE, and design interior finishes to withstand wet floodproofing (removable flooring, washable walls). Option 2 is typical for California and costs $15,000–$25,000 including engineering and permitting. Utility situation: the junior ADU shares all utilities with the main house (water, sewer, electrical, gas); no sub-metering required because it is not a separate unit (it is legally an accessory to the main dwelling). However, the electrical system must be expanded to handle the new room, and the plumbing must support the separate bathroom; city requires a licensed electrician and plumber for these upgrades. Plan check timeline is 8-10 weeks due to flood-mitigation review (the city requires a flood-compliance engineer to sign off). Permit fees: building permit $2,500 (1.5% of $170,000 estimated cost; cheaper than detached or full ADU), impact fees $1,500 (sometimes waived for junior ADUs by some jurisdictions, but San Bernardino typically applies them), plan review $1,500. Total permit cost: $5,500. Flood-engineering and mitigation cost: $15,000–$25,000 (engineering $3,000–$5,000, construction $12,000–$20,000). Construction cost for the ADU room itself: $120,000–$170,000 (framing, HVAC, electrical, plumbing, finishes). Timeline: 8-10 weeks permit, 10-12 weeks construction. The flood-zone overlay and floodproofing requirement are what make San Bernardino's flood-prone lots different from non-flood jurisdictions; without flood review, this would be a 5-6 week permit.
Junior ADU, within main-dwelling footprint | 400 sq ft, 1 bed/1 bath | Separate entrance, shared kitchen | Flood zone AE (6.5 ft BFE) | Floodproofing required per FEMA guidelines | No sub-meter (not separate unit) | Licensed electrician + plumber required for utility expansion | Building permit $2,500 + impact fees $1,500 + plan review $1,500 | Total permit: $5,500 | Flood engineering + mitigation: $15,000–$25,000 additional | Timeline: 8-10 weeks permit, 10-12 weeks construction

Every project is different.

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San Bernardino's 60-day shot clock and AB 671: why the clock matters

California AB 671 (effective 2021) requires cities to approve or deny ADU permits within 60 calendar days. San Bernardino's building department must make a decision by day 60 or the permit is deemed approved — automatically. This is not a soft guideline; applicants have won deemed-approved ADU permits by day 60 in San Bernardino when the city's plan-check team couldn't finish in time. The clock starts on the date of initial acceptance (when the city confirms that the application package is complete and ready for substantive review). Many applicants in San Bernardino first encounter delays in the 'application completeness' phase: the city's intake staff may request missing documents (survey, site plan, utility letters) before day 1 even starts. Pro tip: call the building department before submitting (or use their online portal's checklist) to confirm that your application is complete. Once day 1 begins, you have exactly 60 days. If the city issues plan-check comments on day 45, you have 15 days to respond; if your response is inadequate, the city can deny on day 60, but they cannot delay the decision past day 60.

In practice, San Bernardino's building department rarely lets an ADU go to deemed approval because it creates liability and confusion about what was actually approved. Instead, the city accelerates plan check in the last 2-3 weeks if needed. However, if you have a complex project (hillside, flood, geotechnical) and the city has genuinely not completed review, you will be approved on day 60 unless you request a continuance (which pauses the clock). Most applicants don't request continuances; they accept the deemed approval and move to construction. This is where owner-builders have an advantage in San Bernardino: if your permit is deemed approved and you didn't intend to wait for final-finalized plan check, you can still go to building permit issuance and start construction under the deemed-approved permit, with inspections and final sign-off tied to the building code at the time of permit issuance.

San Bernardino's hillside and flood-zone overlays: the deal-killers for small-lot ADUs

San Bernardino's geography is split: valley floor (flat, floodable) and foothills (steep, fire-prone, geotechnically complex). About 40% of the city's single-family residential lots are in a hillside zone (slopes >15%) or fire-hazard zone (WUI — wildland-urban interface). Another 25% are in a flood zone (FEMA zones A, AE, X — mostly along the Santa Ana River corridor and Lytle Creek drainage). If your lot is in either, ADU feasibility drops. Hillside lots require a geotechnical report ($2,500–$4,000, 3-4 week turnaround). Fire-zone lots require defensible-space plans, Class A roofing, and ember-resistant venting ($5,000–$8,000 in compliance costs). Flood-zone lots require floodproofing or elevation ($15,000–$25,000 in engineering and construction). The city's geotechnical report template requires evaluation of liquefaction (common in valley floor), expansive soil (common in foothills), and slope stability. On a 20% hillside with expansive clay, a detached ADU foundation must be post-tensioned slab or pier-and-beam per IRC R403.1.8, adding $8,000–$12,000 to foundation cost alone. This is why many San Bernardino ADU projects die in pre-planning: the applicant buys a hillside lot for $500,000, spends $3,000 on a geotechnical report, learns that the soil is 'very high' liquefaction risk and requires special foundation design, and the total ADU cost balloons to $400,000+ (versus $300,000 on a flat lot). The building department cannot waive these overlays; they are tied to the lot, not the project.

If your lot is outside all overlays (flat, non-flood, non-fire), you are in the sweet spot — San Bernardino approves these ADUs routinely and quickly. The city publishes its overlays on its website and in the General Plan; before you buy a lot or hire an architect, run the parcel number through the city's GIS mapping tool (typically free and public). This will show you flood zones, fire zones, and geotechnical concerns instantly. If the lot is in multiple overlays, budget $15,000–$20,000 in pre-construction studies alone, plus a minimum 10-week permit timeline.

City of San Bernardino Building and Safety Department
San Bernardino City Hall, 300 North D Street, San Bernardino, CA 92401
Phone: (909) 384-5600 or see city website for building department direct line | https://www.sbcity.org/ (search for 'building permits' or 'permit portal' on the city website for online application system)
Monday-Friday, 8:00 AM - 5:00 PM (closed city holidays; verify before visiting)

Common questions

Can I build an ADU on my single-family lot in San Bernardino without the city's permission?

No. California law (AB 881) requires the city to approve an ADU on your single-family lot, but you must still get a permit and pass inspections. The state law strips the city's ability to say 'no' based on zoning objections, but the permit itself is mandatory. Unpermitted ADUs face stop-work orders, forced removal, and title liability ($50,000–$150,000 loss on resale).

What is the difference between a junior ADU and a regular ADU in San Bernardino?

A junior ADU (up to 500 sq ft) is carved out of the existing main dwelling (no new roof/walls) and shares the kitchen with the main house; it is ministerial and counts as part of the main dwelling for utility and parking purposes. A regular ADU (up to 1,200 sq ft or 25% of main house) is a separate structure (detached, garage conversion, or above-garage) with its own kitchen and entrance; it requires separate sub-metering and is also ministerial in San Bernardino but technically a separate use-and-occupancy. Both require building permits; junior ADUs are usually cheaper and faster.

Do I need a separate water and sewer meter for my ADU in San Bernardino?

Yes, if the ADU is a separate unit with its own kitchen and entrance. California Government Code 65852.22 requires sub-metering or separate service if the ADU does not share a kitchen with the main house. San Bernardino Water Department charges $2,000–$5,000 to install a sub-meter; your plumber will handle the connection. Junior ADUs that share a kitchen do not require separate meters because they are part of the main dwelling.

How long does it take to get an ADU permit in San Bernardino?

Standard ADUs (flat lot, non-flood, non-fire zone): 6-8 weeks. Complex ADUs (hillside, flood zone, or fire zone): 10-14 weeks. The state shot clock is 60 days; if the city doesn't issue or deny within 60 days, your permit is deemed approved. Most San Bernardino ADU permits issue within 55-60 days to avoid deemed approval.

Can I act as the builder for my own ADU in San Bernardino?

Yes, under California Business & Professions Code 7044 (owner-builder), you can do most of the work yourself. However, electrical and plumbing must be done by a licensed contractor or by you if you hold a Class C-10 (electrical) or C-36 (plumbing) license. Owner-builder permits don't reduce permit fees but can save $15,000–$30,000 in labor.

What if my San Bernardino lot is in a fire zone or flood zone — does that kill my ADU project?

Not necessarily, but it adds significant cost and timeline. Fire-zone ADUs need defensible space (clearing), Class A roofing, and ember vents ($5,000–$8,000). Flood-zone ADUs need floodproofing or elevation to the base flood elevation ($15,000–$25,000). Hillside ADUs need geotechnical reports and special foundation design ($2,500–$4,000 report, $8,000–$12,000 foundation). These are code-required; the city cannot waive them. Budget accordingly and check the city's overlay map before buying a lot.

Can I rent out my ADU in San Bernardino, or must I live in the main house?

California AB 881 eliminated owner-occupancy requirements for most ADUs. San Bernardino allows rental ADUs on single-family lots as long as the ADU is not the only dwelling on the lot (the main house must exist). There is no prohibition on renting both the main house and the ADU as separate rentals, though local income-tax or short-term-rental ordinances may apply separately.

Do I need parking for my ADU in San Bernardino?

No. San Bernardino is classified as a sensitive community under AB 881, which waives parking requirements for ADUs. This is a major advantage compared to high-income cities that can still enforce parking minimums. Even if you are building a 1,200 sq ft ADU with 2 bedrooms, no parking is required by the building code.

What happens if my ADU permit is denied in San Bernardino?

ADU denials are rare in San Bernardino because the city has ministerial approval for compliant ADUs (no discretionary review). Denials typically occur if the unit exceeds the 1,200 sq ft or 25% main-house size cap, violates setbacks due to lot size, or has code compliance issues (egress, foundation, utilities). If denied, you have the right to appeal to the city council or state housing court. Appealing to state court is increasingly successful because state law favors ADUs.

How much will my ADU permit cost in San Bernardino?

Typical range: $5,500–$12,000. Breaking down: building permit ($3,500–$6,000, based on construction valuation), impact fees ($1,500–$4,000), plan review ($1,500–$2,500), and specialty reviews (geotechnical $2,500–$4,000 if hillside, flood engineering $1,000–$2,000 if flood zone). Standard flat-lot ADUs cost $8,000–$10,000 total permit fees; complex overlay ADUs cost $10,000–$15,000.

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Disclaimer: This guide is based on research conducted in May 2026 using publicly available sources. Always verify current accessory dwelling unit (adu) permit requirements with the City of San Bernardino Building Department before starting your project.

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