Fontana allows ADUs and JADUs on lots with a single-family or multifamily home under Fontana Municipal Code Sec. 30-467, amended by Ordinance No. 1966 (April 2025) and Ordinance No. 1983 (February 2026) to match state law. A detached ADU can be up to 1,200 sq ft (Class 2, locally regulated) or 800 sq ft with only the state minimum standards (Class 1); an attached ADU up to 50% of the house or 850 sq ft (studio/1-bed) / 1,000 sq ft (2+ beds), whichever is larger; a JADU up to 500 sq ft. Side and rear setbacks are 4 ft, the front setback 18 ft for new construction, and height 16 ft (18 ft near transit). The city publishes three pre-approved detached plans (462, 738 and 1,143 sq ft), applications go through the Build Fontana portal with a first plan check of about 3-4 weeks, and city impact fees are waived on units of 750 sq ft or less.
Outside city limits? If your property is in unincorporated San Bernardino County (not within Fontana's boundaries), different rules apply — see our San Bernardino County (unincorporated) ADU rules.
Zoning & Size Requirements [1][2][3][4][5][6]
Yes — Fontana allows ADUs. A detached ADU can typically be up to 1,200 sq ft under current California and Fontana zoning rules.
See what this means for your lot — ask Fontana ADU builders for a quote →
| Allowed Zones | Any lot zoned for residential use with an existing or proposed single-family or multifamily dwelling, including the R-1, R-2, R-3 and residential specific-plan and form-based-code areas (FMC Sec. 30-467; Gov. Code 66314). Eligibility depends on the property's zoning; check it on the city's Zoning and General Plan interactive map or call Planning at (909) 350-6718. |
| Max Size (Detached) | 1,200 sq ft for a Class 2 (locally regulated) detached ADU; 800 sq ft for a Class 1 detached ADU, which gets only the state minimum standards (no design review, no parking). On a multifamily lot each detached ADU is capped at 850 sq ft, or 1,000 sq ft with more than one bedroom (ADU Information Sheet, March 2026; Sec. 30-467). |
| Max Size (Attached) | 50% of the primary dwelling's floor area or 850 sq ft (studio/1-bedroom) / 1,000 sq ft (2+ bedrooms), whichever is larger. Conversions of existing living space or an existing accessory building have no size cap (ADU Information Sheet, March 2026). |
| Max Size (JADU) | 500 sq ft, created inside the existing or proposed single-family home or its attached garage; needs its own kitchen and either its own bathroom or shared use of the house bathroom; one JADU per lot (Sec. 30-467; Gov. Code 66333). |
| Max Height | 16 ft for a detached ADU; 18 ft (city sheet: 16-18 ft for Class 2) where the lot is within 1/2 mile walking distance of a major transit stop or holds a multistory multifamily building, plus up to 2 ft for a roof pitch matching the house; an attached ADU may go to 25 ft or the zone's height limit, whichever is lower (Gov. Code 66321; Sec. 30-467). A Class 2 detached unit must be architecturally compatible with the main house. |
| Max Units | Single-family lot: up to 1 JADU + 1 Class 1 detached ADU (800 sq ft) + 1 conversion ADU (ADU Information Sheet, March 2026). Multifamily lot: converted ADUs in non-livable space up to 25% of the existing units (at least 1), plus up to 8 detached ADUs on a lot with existing multifamily (not more than the number of existing units), or 2 detached ADUs built with a new multifamily building (Ordinance No. 1966, 2025; Gov. Code 66323). |
Setback Requirements [1][2][3][4][5][6]
Fontana requires a rear setback of about 4 ft for a detached ADU, and parking requirements vary by unit size or location. Owner-occupancy is not required — you can rent it out without living on the property.
| Rear Setback | 4 ft minimum for new construction (Sec. 30-467; ADU Information Sheet, March 2026). Conversions of existing structures and their same-footprint rebuilds keep the existing setback (Gov. Code 66314). |
| Side Setback | 4 ft minimum for new construction, attached or detached (Sec. 30-467; ADU Information Sheet, March 2026). |
| Front Setback | 18 ft for a new attached or detached ADU (ADU Information Sheet, March 2026). State law still guarantees room for an 800 sq ft unit: the front setback cannot be used to block a Class 1 ADU that fits nowhere else on the lot (Gov. Code 66321). |
| Parking Required | None for a JADU, a conversion ADU or a Class 1 detached ADU (800 sq ft or less). One space for an attached ADU or a Class 2 detached ADU, waived under the state exemptions in Sec. 30-467 (within 1/2 mile walking distance of transit, historic district, no on-street permit parking, car share within a block). Since Ordinance No. 1966 (2025) the city does not require replacement parking when a garage or carport becomes an ADU (Gov. Code 66322). |
| Owner Occupancy | Not required for an ADU. For a JADU, owner occupancy of the property is required only if the JADU shares a bathroom with the main house; a JADU with its own bathroom is exempt (ADU Information Sheet, March 2026, implementing AB 1154, Gov. Code 66333, effective Jan. 1, 2026). |
| Min Lot Size | No minimum lot size for an ADU or JADU; the state bars local minimum-lot-size rules for ADUs (Gov. Code 66314). Any lot with an existing or proposed home qualifies. |
Permit Process & Fees [7][8][9][10][11][12]
An ADU permit in Fontana goes through a ministerial, by-right review. Typical timeline: Building & Safety's published plan-check times: first review about 3-4 weeks, each recheck about 2 weeks. State law requires a decision within 60 days of a complete application and deems it approved if the city misses the deadline (Gov. Code 66317, SB 543, Jan. 2026). Permit fees: No flat ADU fee: building permit and plan check are valuation-based per the Comprehensive Fee Schedule (Res. 2024-054, 9/1/2024), plus Planning plan check $191, Engineering $120 and Fire $90 per submittal and small state/archive add-ons. Get a quote from Building & Safety, (909) 350-7640.
| Approval Process | Ministerial (no hearing): register and submit plans electronically through the Build Fontana portal, or on paper at the Building & Safety counter, 8353 Sierra Ave. Building & Safety routes the set to Planning, Fire and Engineering; Planning checks Sec. 30-467 standards and Class 2 design compatibility. Use one of the three pre-approved plans (462, 738 or 1,143 sq ft) or your own drawings; a site plan and permit are still required with a standard plan. |
| Review Timeline | Building & Safety's published plan-check times: first review about 3-4 weeks, each recheck about 2 weeks. State law requires a decision within 60 days of a complete application and deems it approved if the city misses the deadline (Gov. Code 66317, SB 543, Jan. 2026). |
| Permit Fees | No flat ADU fee: building permit and plan check are valuation-based per the Comprehensive Fee Schedule (Res. 2024-054, 9/1/2024), plus Planning plan check $191, Engineering $120 and Fire $90 per submittal and small state/archive add-ons. Get a quote from Building & Safety, (909) 350-7640. |
| Impact Fees | None on an ADU of 750 sq ft or less (Gov. Code 66311.5(c)(1)). Above 750 sq ft, the city's per-unit single-family development fees (about $20,600 in Planning fees plus $8,620 sewer expansion and $1,023 sewer connection per unit on the 10/2024 sheet) are charged in proportion to the ADU's share of the main house's floor area. IEUA sewer and school-district fees are billed separately. |
| Plan Check | First review about 3-4 weeks; rechecks about 2 weeks after corrected plans are resubmitted; over-the-counter issuance only for work that needs no plan check. Status is tracked in the Build Fontana portal or at (909) 350-7640. Fire District reviews (NFPA 13D sprinklers) run separately with a 15-working-day goal. |
| Pre-Approved Plans | Yes. Fontana's Standard ADU Plans program (AB 1332, Gov. Code 65852.27) posts three pre-approved detached plans: 462 sq ft (1 bed/1 bath), 738 sq ft (2 bed/2 bath) and 1,143 sq ft (3 bed/2 bath). The plan sets are free to download from the city site; you still submit a site-specific plan and pay permit fees. |
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Construction Costs [13][14][15][16]
Building an ADU in Fontana typically costs $175,000-$320,000 ($180-$300 per sq ft); a garage conversion runs $75,000-$150,000.
See what this means for your lot — ask Fontana ADU builders for a quote →
| Average Build Cost | $175,000-$320,000 |
| Cost per Sq Ft | $180-$300 |
| Garage Conversion | $75,000-$150,000 |
| Prefab ADU (Installed) | $120,000-$250,000 |
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Rental Income Potential [17][18][19]
A 2-bedroom ADU in Fontana rents for around $2,100-$2,300/mo, an estimated 7-15% gross rental yield on a $175,000-$320,000 detached build at $1,750-$2,300/mo (about a 7-15 year simple payback); roughly 14-35% gross on a $75,000-$150,000 garage conversion; before taxes, vacancy and financing.
| Avg Rent (1 Bedroom) | $1,750-$1,900/mo |
| Avg Rent (2 Bedroom) | $2,100-$2,300/mo |
| Short-Term Rental | A JADU may not be rented for less than 30 days (Gov. Code 66333, AB 1154). The city's minimum rental term for ADUs sits in Sec. |
| Est. Annual ROI | 7-15% gross rental yield on a $175,000-$320,000 detached build at $1,750-$2,300/mo (about a 7-15 year simple payback); roughly 14-35% gross on a $75,000-$150,000 garage conversion; before taxes, vacancy and financing |
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Recent Law Changes
What's Changed Recently
- Feb. 10, 2026: City Council acted on Ordinance No. 1983, the permanent amendment to Sec. 30-467 for the Jan. 1, 2026 state changes (AB 1154 JADU owner-occupancy and 30-day JADU rental minimum; SB 543 60-day deemed approval); the city's ADU Information Sheet was reissued in March 2026 to match
- Jan. 1, 2026: SB 543 - an ADU application is deemed approved if the city does not act within 60 days of a complete application (Gov. Code 66317)
- Jan. 1, 2026: AB 1154 - owner occupancy may be required for a JADU only if it shares a bathroom with the main house; JADU rentals must be longer than 30 days (Gov. Code 66333)
- April 8, 2025: Ordinance No. 1966 adopted (4-0), replacing the Nov. 12, 2024 urgency ordinance: up to 8 detached ADUs on existing multifamily lots, no replacement parking when a garage is converted, and permits cannot be denied for unpermitted ADUs/JADUs built before Jan. 1, 2020 (AB 2533 / SB 1211)
- 2025: Standard ADU Plans program launched under AB 1332 with three pre-approved detached plans (462, 738 and 1,143 sq ft)
- Sept. 2026: entry re-verified against the March 2026 ADU Information Sheet, the Standard ADU Plans page, the Res. 2024-054 development fee sheet and the Plan Check page; unsourced claims ("permit fees waived", "~60 days with pre-approved plans") removed
Tips for Building an ADU in Fontana
- Pick your class before you design: a Class 1 detached ADU (800 sq ft or less, 16 ft, 4 ft setbacks) gets no parking and no design review; a Class 2 unit (up to 1,200 sq ft) needs one parking space unless exempt and must match the house architecturally (Sec. 30-467).
- Stay at 750 sq ft or less to avoid city impact fees entirely (Gov. Code 66311.5); the city's single-family fee sheet totals about $20,600 in Planning fees plus $9,643 in sewer fees per unit, and a larger ADU pays a proportional share of that.
- Worked example (our arithmetic from the 10/2024 fee sheet): a 1,000 sq ft ADU behind a 2,000 sq ft house owes about 50% of the per-unit fees, roughly $10,300 in Planning impact fees plus about $4,800 in city sewer fees, before building permit, IEUA and school fees.
- The three free Standard ADU Plans (462, 738, 1,143 sq ft) are all detached; the 462 and 738 sq ft plans stay under the 750 sq ft impact-fee line, the 1,143 sq ft plan does not.
- Built an ADU without a permit before 2020? Since Jan. 1, 2025 the city must issue a legalizing permit unless the unit is substandard; Building & Safety publishes a Substandard Building Checklist (Nov. 2025) for unpermitted ADUs/JADUs (Gov. Code 66311.7, formerly 66332).
- On a multifamily lot you can add converted ADUs in garages, storage or basements up to 25% of the existing unit count and up to 8 detached ADUs, each 850 sq ft (1,000 sq ft with 2+ bedrooms).
- Budget the whole timeline, not just the 60-day clock: a first plan check takes about 3-4 weeks and each recheck about 2 weeks, so a clean submittal on a standard plan is the fastest route.
- Cost basis: Inland Empire figures from CaliFirst Remodel (May 2026), LA Metro Home Finder (June 2026), Construction Station (Sept. 2026) and Autonomous (Feb. 2026); rents from Zumper (Sept. 19, 2026), RentCafe (Aug. 31, 2026) and HUD FY2026 Fair Market Rent for the Riverside-San Bernardino-Ontario metro ($1,777 1BR, $2,201 2BR).
- Contacts: Planning (909) 350-6718, planning@fontanaca.gov; Building & Safety (909) 350-7640, building@fontanaca.gov, 8353 Sierra Ave; Fire Prevention plan check (909) 428-8891.
- Cost basis (2026-09-20 re-verification): short term allowed: A JADU may not be rented for less than 30 days (Gov. Code 66333, AB 1154). The city's minimum rental term for ADUs sits in Sec. 30-467, which could not be read online this month; state law lets cities require terms over 30 days, so plan on 30-day-plus tenancies and confirm with Planning, (909) 350-6718.
ADU Builders in Fontana
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Sources & References
All data on this page is sourced from official government records and verified market data. View our full methodology.
- Single-Family and Multi-Family Accessory Dwelling Unit Types - ADU Information Sheet (updated March 2026) | City of Fontana Planning government — Accessed 2026-09-20
- Fontana Municipal Code Sec. 30-467, Accessory dwelling units and junior accessory dwelling units (Municode; Cloudflare-blocked on 2026-09-20, read via the city's March 2026 information sheet) government — Accessed 2026-09-20
- Notice of Exemption, Municipal Code Amendment No. 24-006 - Urgency Ordinance Amending Sec. 30-467 (filed 11/15/2024) | CEQAnet government — Accessed 2026-09-20
- Notice of Exemption, Municipal Code Amendment No. 24-0006 - Chapter 30 ADU/JADU amendment (filed 4/10/2025, permanent Ordinance No. 1966) | CEQAnet government — Accessed 2026-09-20
- FAQ: Can I build an accessory dwelling unit (ADU) or junior accessory dwelling unit (JADU)? | City of Fontana Planning government — Accessed 2026-09-20
- AB 1154 (Carrillo, 2025), Junior accessory dwelling units - Gov. Code 66333 as amended (chaptered 10/10/2025) | California Legislative Information government — Accessed 2026-09-20
- Standard ADU Plans - three AB 1332 pre-approved detached plans (462, 738, 1,143 sq ft) | City of Fontana Building & Safety government — Accessed 2026-09-20
- Plan Check - submission, review process (first review 3-4 weeks, rechecks 2 weeks) | City of Fontana Building & Safety government — Accessed 2026-09-20
- Development Fees sheet - Building & Safety, Planning and Engineering fees, Update of User Fees 09/01/2024 per Resolution 2024-054 (rev. 10/07/2024) | City of Fontana government — Accessed 2026-09-20
- Substandard Building Checklist for Unpermitted Accessory Dwelling Units and Junior Accessory Dwelling Units (Nov. 2025) | City of Fontana Building & Safety government — Accessed 2026-09-20
- FAQ: What is the fee to file for a building permit or to submit plans? | City of Fontana Building & Safety government — Accessed 2026-09-20
- Fire Prevention - Permits, Inspections & Fees (15-working-day plan review goal) | Fontana Fire Protection District government — Accessed 2026-09-20
- ADU Costs in California (2026): City-by-City Numbers - Inland Empire section (May 28, 2026) | CaliFirst Remodel industry — Accessed 2026-09-20
- ADU Permit Rules: Inland Empire Cities 2026 - cost per sq ft and garage conversions (June 12, 2026) | LA Metro Home Finder industry — Accessed 2026-09-20
- ADU Contractors Inland Empire - garage conversion, JADU and detached cost ranges | Construction Station industry — Accessed 2026-09-20
- Prefab ADUs in Southern California: Complete Guide for 2026 (Feb. 26, 2026) | Autonomous industry — Accessed 2026-09-20
- Fontana, CA rent research - median rents by bedroom (updated Sept. 19, 2026) | Zumper industry — Accessed 2026-09-20
- Average Rent in Fontana, CA (as of Aug. 31, 2026) | RentCafe industry — Accessed 2026-09-20
- FY 2026 Fair Market Rents, Riverside-San Bernardino-Ontario, CA MSA (METRO40140M40140) | HUD User government — Accessed 2026-09-20
Frequently Asked Questions
Can I build an ADU in Fontana?
Yes. ADUs are allowed in Any lot zoned for residential use with an existing or proposed single-family or multifamily dwelling, including the R-1, R-2, R-3 and residential specific-plan and form-based-code areas (FMC Sec. 30-467; Gov. Code 66314). Eligibility depends on the property's zoning; check it on the city's Zoning and General Plan interactive map or call Planning at (909) 350-6718. in Fontana. The maximum size for a detached ADU is 1,200 sq ft for a Class 2 (locally regulated) detached ADU; 800 sq ft for a Class 1 detached ADU, which gets only the state minimum standards (no design review, no parking). On a multifamily lot each detached ADU is capped at 850 sq ft, or 1,000 sq ft with more than one bedroom (ADU Information Sheet, March 2026; Sec. 30-467).. Owner-occupancy is not required, so you can rent out the ADU.
How much does an ADU cost in Fontana?
ADU construction in Fontana typically costs $175,000-$320,000. Garage conversions run $75,000-$150,000, and prefab ADUs cost $120,000-$250,000.
How much can I rent an ADU for in Fontana?
Average ADU rents in Fontana are $1,750-$1,900/mo for a 1-bedroom and $2,100-$2,300/mo for a 2-bedroom unit.
Do I need parking for an ADU in Fontana?
None for a JADU, a conversion ADU or a Class 1 detached ADU (800 sq ft or less). One space for an attached ADU or a Class 2 detached ADU, waived under the state exemptions in Sec. 30-467 (within 1/2 mile walking distance of transit, historic district, no on-street permit parking, car share within a block). Since Ordinance No. 1966 (2025) the city does not require replacement parking when a garage or carport becomes an ADU (Gov. Code 66322).. Check with Fontana planning department for the latest California ADU parking rules, as many states have relaxed requirements in recent years.
How long does it take to get an ADU permit in Fontana?
The permit review timeline in Fontana is Building & Safety's published plan-check times: first review about 3-4 weeks, each recheck about 2 weeks. State law requires a decision within 60 days of a complete application and deems it approved if the city misses the deadline (Gov. Code 66317, SB 543, Jan. 2026).. Permit fees: No flat ADU fee: building permit and plan check are valuation-based per the Comprehensive Fee Schedule (Res. 2024-054, 9/1/2024), plus Planning plan check $191, Engineering $120 and Fire $90 per submittal and small state/archive add-ons. Get a quote from Building & Safety, (909) 350-7640.
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