Yes. Folsom allows ADUs on any parcel zoned for single-unit, two-unit or multi-unit housing that has an existing or proposed home (FMC 17.105.010, rewritten by Ord. 1361, adopted April 14, 2026, effective May 14, 2026). A detached ADU may reach 1,000 sq ft with two or more bedrooms (850 sq ft with one), 25 ft in height, and 4-ft side and rear setbacks; a new detached unit of 800 sq ft or less at state heights is a '66323 unit' that skips design review entirely. The permit is a ministerial building permit with a flat $4,852 fee ($2,329 for a JADU) under the July 1, 2026 schedule, a $400 design-review fee only for larger units, no city impact fees at 750 sq ft or less, and a 60-day decision clock with deemed approval. ADUs must rent for 30 days or longer and may be sold separately to a qualified buyer under Gov. Code 66341.
Zoning & Size Requirements [1][2][3][4][5]
Yes — Folsom allows ADUs. A detached ADU can typically be up to 1,000 sq ft under current California and Folsom zoning rules.
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| Allowed Zones | Any parcel zoned for single-unit, two-unit or multi-unit residential use with an existing or proposed primary dwelling (FMC 17.105.010(D)); JADUs only on single-unit parcels. Historic District parcels add objective architectural-style rules (17.105.200) unless the unit is a 66323 unit. |
| Max Size (Detached) | 1,000 sq ft with 2 or more bedrooms, 850 sq ft with 1 bedroom or fewer, measured as interior living space, minimum 150 sq ft (FMC 17.105.150(B)(2)). A new detached unit of 800 sq ft or less with 4-ft setbacks is a '66323 unit' exempt from design review, and no standard may preclude an 800 sq ft ADU (17.105.150(C)(2)). Detached ADUs on two-unit and multi-unit lots are capped at 800 sq ft (17.105.170(B)(2)). |
| Max Size (Attached) | 1,000 sq ft with 2 or more bedrooms or 850 sq ft with 1 bedroom or fewer, and no more than 50% of the existing primary dwelling's floor area (FMC 17.105.140(B)(2)). A conversion of space inside the house, plus up to 150 sq ft for an entrance, is a 66323 unit with no local size cap (17.105.140(A)). |
| Max Size (JADU) | 500 sq ft, entirely within the single-unit home, with its own exterior entrance and an efficiency kitchen; minimum 150 sq ft (FMC 17.105.160). A deed restriction on the city's template (Form CD-P515) is recorded before the building permit issues. |
| Max Height | Detached: 25 ft or the height of the main house, whichever is less, measured finished grade to peak (FMC 17.105.150(B)(5)); within 50 ft of a listed historic structure only the state heights apply. 66323 units: 16 ft, 18 ft within 1/2 mile of a major transit stop or where the roof pitch matches the house, 20 ft with both (city checklist CD-P214; Gov. Code 66321). Attached: the zone's height, but 25 ft for any part inside the primary dwelling's setback area (17.105.140(B)(5)). |
| Max Units | Single-unit lot: 1 attached or detached ADU + 1 conversion ADU (inside the house or an existing accessory building) + 1 JADU + 1 new detached 66323 ADU (FMC 17.105.120(A)(1)). Two-unit and multi-unit lots: conversions of non-livable space up to 25% of existing units, plus up to 2 detached ADUs with a proposed building or up to 8 detached with an existing building, never more than the number of existing units (17.105.120(A)(2)). Parcels from an SB 9 lot split: 2 units total. |
Setback Requirements [1][2][3][4][5]
Folsom 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 (FMC 17.105.150(B)(3)); the city recommends 5 ft to avoid extra Fire Code construction requirements. No setback change for a conversion of an existing house or accessory building, or for an ADU built on top of an existing accessory building that already sits closer than 4 ft. |
| Side Setback | 4 ft minimum, 5 ft recommended by the Building Division to avoid Fire Code upgrades; none for conversions of existing space. A detached ADU must be at least 6 ft from the house and from any other accessory building other than a fence or wall (FMC 17.105.150(B)(3)). |
| Front Setback | Attached units use the zone's front setback (FMC 17.105.140(B)(3)); a detached ADU may not break the front plane of the primary dwelling (17.105.150(B)(3)). The ADU may cover no more than 40% of the rear yard and the zone's lot-coverage limit applies, except for 66323 units of 800 sq ft or less, which are also exempt from required open space (17.105.150(B)(4), 17.105.130(D)). |
| Parking Required | 1 space per ADU or per bedroom, whichever is less; a driveway or tandem space counts (FMC 17.105.180(A)). Not required within 1/2 mile walking distance of public transit, in the Historic District, for a unit inside the house or an existing accessory building, near a car-share vehicle, or when permitted with a new home; no replacement parking when a garage is converted (17.105.180(B)-(C)). The city publishes an ADU Parking Requirement Map. |
| Owner Occupancy | Not required for ADUs. JADUs: required only when the JADU shares a bathroom with the main house (FMC 17.105.160(B)(4), matching Gov. Code 66333 as amended by AB 1154, effective Jan 1, 2026); a JADU with its own bathroom has no owner-occupancy rule. |
| Min Lot Size | No minimum lot size anywhere in FMC 17.105; the zone's lot-coverage and pervious-surface standards still apply to units that are not 66323 units (17.105.150(B)(4)). |
Permit Process & Fees [6][7][8][9][10]
An ADU permit in Folsom goes through a ministerial, by-right review. Typical timeline: Completeness notice within 15 business days; decision within 60 days of a complete application, deemed approved if the city misses it (FMC 17.105.050; Gov. Code 66317). The city says merged design review saves an estimated 3-4 weeks and a pre-reviewed Master Plan about 30 days more. Permit fees: Flat building permit fee of $4,852 per detached or attached ADU and $2,329 per JADU, covering plan review and inspections (Res. 11481, effective July 1, 2026), plus an $81 processing fee and state surcharges; design review for a non-66323 unit adds $400 (Director level).
| Approval Process | Ministerial building permit filed in the Folsom ePermit Center under permit type 'ADU – Accessory Dwelling Unit' with the Residential Projects Checklist (Form B210) and the optional zoning checklist for your ADU type (Forms CD-P213/214/215). Units that are not 66323 units get a concurrent ministerial design review by the Community Development Director inside the building permit (FMC 17.105.110, 17.06.045); no Planning or Historic District Commission hearing. Planning assigns the ADU's address after issuance. |
| Review Timeline | Completeness notice within 15 business days; decision within 60 days of a complete application, deemed approved if the city misses it (FMC 17.105.050; Gov. Code 66317). The city says merged design review saves an estimated 3-4 weeks and a pre-reviewed Master Plan about 30 days more. |
| Permit Fees | Flat building permit fee of $4,852 per detached or attached ADU and $2,329 per JADU, covering plan review and inspections (Res. 11481, effective July 1, 2026), plus an $81 processing fee and state surcharges; design review for a non-66323 unit adds $400 (Director level). |
| Impact Fees | No city impact fees for an ADU of 750 sq ft or less or a JADU of 500 sq ft or less (FMC 17.105.060(C)); above 750 sq ft each city fee is prorated by ADU floor area divided by primary-dwelling floor area. Water and sewer connection or capacity charges are not charged unless the ADU is built with a new house (17.105.060(B)). The July 1, 2026 North of 50 schedule totals about $26,200 in city impact fees for a new single-family home (roads $9,903, park equipment $8,532, general $1,936, fire $1,316, drainage $1,257, water $1,194, light rail $878, police $728, smaller items), so a 1,000 sq ft ADU behind a 2,000 sq ft house would owe roughly half; the Folsom Plan Area south of Hwy 50 has its own higher schedule. School district fees are collected separately. |
| Plan Check | Plan check is bundled into the flat ADU permit fee and covers up to three review cycles; a fourth cycle, revisions and deferred submittals bill at $194 per hour and expedited review costs 1.5x (Res. 11481, Building Fees Sec. D). Side or rear setbacks under 5 ft trigger extra Fire Code construction requirements; retaining walls over 4 ft or grading over 50 cubic yards need separate permits; work on a protected tree needs a Tree Permit. |
| Pre-Approved Plans | Not available yet — Folsom launched an ADU Master Plan program under Gov. Code 65852.27 (designers submit detached ADU plans for pre-review; a homeowner using one, with no deviations, cuts permit time by an estimated 30 days), but the city's approved-plan gallery listed no plans as of Sept 20, 2026. |
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Construction Costs [11][12][13][14]
Building an ADU in Folsom typically costs $170,000-$400,000 ($250-$500 per sq ft); a garage conversion runs $90,000-$200,000.
See what this means for your lot — ask Folsom ADU builders for a quote →
| Average Build Cost | $170,000-$400,000 |
| Cost per Sq Ft | $250-$500 |
| Garage Conversion | $90,000-$200,000 |
| Prefab ADU (Installed) | $170,000-$340,000 |
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Rental Income Potential [15][16]
A 2-bedroom ADU in Folsom rents for around $2,200-$2,950/mo, an estimated 7-14% gross rental yield on a $250,000-$400,000 detached build renting at $2,200-$2,950/mo; a $90,000-$200,000 garage conversion at $1,650-$2,400/mo can gross 10-25% (estimates before taxes, vacancy and financing).
| Avg Rent (1 Bedroom) | $1,650-$2,400/mo |
| Avg Rent (2 Bedroom) | $2,200-$2,950/mo |
| Short-Term Rental | No — an ADU or JADU may be rented only for 30 days or longer (FMC 17.105.070(A)), and the city's ADU page states ADUs cannot be used as vacation rentals. |
| Est. Annual ROI | 7-14% gross rental yield on a $250,000-$400,000 detached build renting at $2,200-$2,950/mo; a $90,000-$200,000 garage conversion at $1,650-$2,400/mo can gross 10-25% (estimates before taxes, vacancy and financing) |
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Recent Law Changes
What's Changed Recently
- Sept 20, 2026 re-verification: every standard re-read against FMC 17.105 as codified (current through Ord. 1369, April 28, 2026), Ord. 1361, the July 1, 2026 fee schedule (Res. 11481) and the city's May 14, 2026 checklists; flat $4,852 permit fee, $400 design-review fee, the empty Master Plan program, the 800 sq ft multi-unit cap and the 5-ft Fire Code recommendation added
- Ord. 1361 (introduced March 24, adopted April 14 by a 5-0 vote, effective May 14, 2026) repealed and re-enacted FMC Chapter 17.105 to conform with Gov. Code 66310-66342; design review merged into the building permit and Commission hearings for ADUs ended
- July 1, 2026: Resolution 11481 set flat ADU permit fees ($4,852 ADU, $2,329 JADU) and a $400 Director-level design-review fee for non-exempt ADUs; North of 50 and Plan Area impact fee schedules (dated July 21, 2026) restate $0 for ADUs of 750 sq ft or less
- ADU Master Plan program under Gov. Code 65852.27 launched with a 30-day estimated time saving; the approved-plan gallery was still empty in September 2026
- AB 1154 codified: JADU owner-occupancy applies only where the JADU shares a bathroom with the primary dwelling (FMC 17.105.160(B)(4)); a new 'Carriage House' above-garage style was added for the Historic District
Tips for Building an ADU in Folsom
- Keep a new detached ADU at 800 sq ft or less with 4-ft setbacks and a 16-ft peak (18-20 ft near a major transit stop or with a matching roof pitch) to qualify as a 66323 unit: no design review, no $400 review fee, no Historic District style rules, and the lot-coverage and open-space limits do not apply
- Stay at 750 sq ft or less to owe $0 city impact fees; every square foot above that prorates the full single-family fee package (about $26,200 north of Hwy 50 on the 2026 schedule) by ADU-to-house floor area, so a 1,000 sq ft ADU behind a 2,000 sq ft house owes roughly $13,000
- Budget about $5,200 in city fees for a design-review-exempt ADU: the $4,852 flat permit, the $81 processing fee, the 5% General Plan surcharge on the permit fee and a few dollars of state SMI and SB 1473 fees; the city's Impact Fee Estimate Data Sheet gives a written estimate if you go over 750 sq ft
- Draw side and rear setbacks at 5 ft rather than the 4-ft minimum: the city's Master Plan page says 4 ft triggers extra Fire Code construction requirements, and a detached unit must also sit 6 ft from the house and any other structure
- In the Historic District a non-exempt ADU must follow one of the prescribed styles for its subarea (Queen Anne, Delta, Italianate, Spanish Eclectic, Craftsman, Carriage House; 1950s Ranch in Persifer-Dean); the Carriage House style is for above-garage units and caps the garage at 800 sq ft
- Cost basis: Sacramento-region 2026 contractor guides (Good Life Construction, Apr 28, 2026; Upside ADU, Jun 12, 2026; ADU Wizard 2026; Result Construction 2026) put detached builds at $250-$500 per sq ft and garage conversions at $90,000-$200,000; rents run from Zumper's Folsom listing medians (Sept 20, 2026: 1BR $1,645, 2BR $2,195) to HUD's FY2026-FY2027 Small Area FMRs for ZIP 95630 (1BR $2,380-$2,450, 2BR $2,920-$3,010, gross rent including utilities)
- Separate sale: FMC 17.105.070(B) lets an ADU be sold to a qualified buyer separately from the house under Gov. Code 66341; a JADU cannot be sold separately (17.105.160(B)(3))
- Cost basis (2026-09-20 re-verification): short term allowed: No — an ADU or JADU may be rented only for 30 days or longer (FMC 17.105.070(A)), and the city's ADU page states ADUs cannot be used as vacation rentals. An ADU (not a JADU) may be sold separately to a qualified buyer under Gov. Code 66341 (17.105.070(B)).
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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.
- FMC Chapter 17.105 Accessory Dwelling Units (Ord. 1361 § 2, 2026; code current through Ord. 1369, April 28, 2026) Municipal Code — Accessed 2026-09-20
- Ordinance No. 1361 — Repeal and Re-enactment of Chapter 17.105 (adopted April 14, 2026) ordinance — Accessed 2026-09-20
- Accessory Dwelling Units | City of Folsom Planning Department — Accessed 2026-09-20
- Detached ADU Requirements Checklist, Form CD-P214 (rev. 5-14-26) Planning Department — Accessed 2026-09-20
- Gov. Code 66321 (as amended by SB 543, effective January 1, 2026) state_statute — Accessed 2026-09-20
- Community Development Department User Fees effective July 1, 2026 (Resolution No. 11481) fee_schedule — Accessed 2026-09-20
- North of 50 Development Impact Fees and Permit Fees, effective July 1, 2026 (dated 7/21/2026) fee_schedule — Accessed 2026-09-20
- Folsom Plan Area Development Impact Fees and Permit Fees, effective July 1, 2026 (dated 7/21/2026) fee_schedule — Accessed 2026-09-20
- City Updates and Streamlines Requirements for ADUs | City of Folsom News (May 22, 2026) Planning Department — Accessed 2026-09-20
- ADU Master Plan Program – Approved Master Plan Options | City of Folsom Planning Department — Accessed 2026-09-20
- How Much Does It Cost to Build an ADU in Sacramento (updated April 28, 2026) | Good Life Construction industry — Accessed 2026-09-19
- How Much Does an ADU Cost in Sacramento? (updated June 12, 2026) | Upside ADU industry — Accessed 2026-09-19
- How Much Does an ADU Cost in Sacramento in 2026? | ADU Wizard industry — Accessed 2026-09-19
- Garage Conversion ADU in Sacramento: Complete 2026 Guide | Result Construction industry — Accessed 2026-09-19
- HUD Small Area Fair Market Rents FY2026 and FY2027, ZIP 95630 (Sacramento--Roseville--Arden-Arcade HUD Metro FMR Area) Government Data — Accessed 2026-09-20
- Average Rent in Folsom, CA (updated September 20, 2026) | Zumper Market Data — Accessed 2026-09-20
Frequently Asked Questions
Can I build an ADU in Folsom?
Yes. ADUs are allowed in Any parcel zoned for single-unit, two-unit or multi-unit residential use with an existing or proposed primary dwelling (FMC 17.105.010(D)); JADUs only on single-unit parcels. Historic District parcels add objective architectural-style rules (17.105.200) unless the unit is a 66323 unit. in Folsom. The maximum size for a detached ADU is 1,000 sq ft with 2 or more bedrooms, 850 sq ft with 1 bedroom or fewer, measured as interior living space, minimum 150 sq ft (FMC 17.105.150(B)(2)). A new detached unit of 800 sq ft or less with 4-ft setbacks is a '66323 unit' exempt from design review, and no standard may preclude an 800 sq ft ADU (17.105.150(C)(2)). Detached ADUs on two-unit and multi-unit lots are capped at 800 sq ft (17.105.170(B)(2)).. Owner-occupancy is not required, so you can rent out the ADU.
How much does an ADU cost in Folsom?
ADU construction in Folsom typically costs $170,000-$400,000. Garage conversions run $90,000-$200,000, and prefab ADUs cost $170,000-$340,000.
How much can I rent an ADU for in Folsom?
Average ADU rents in Folsom are $1,650-$2,400/mo for a 1-bedroom and $2,200-$2,950/mo for a 2-bedroom unit.
Do I need parking for an ADU in Folsom?
1 space per ADU or per bedroom, whichever is less; a driveway or tandem space counts (FMC 17.105.180(A)). Not required within 1/2 mile walking distance of public transit, in the Historic District, for a unit inside the house or an existing accessory building, near a car-share vehicle, or when permitted with a new home; no replacement parking when a garage is converted (17.105.180(B)-(C)). The city publishes an ADU Parking Requirement Map.. Check with Folsom 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 Folsom?
The permit review timeline in Folsom is Completeness notice within 15 business days; decision within 60 days of a complete application, deemed approved if the city misses it (FMC 17.105.050; Gov. Code 66317). The city says merged design review saves an estimated 3-4 weeks and a pre-reviewed Master Plan about 30 days more.. Permit fees: Flat building permit fee of $4,852 per detached or attached ADU and $2,329 per JADU, covering plan review and inspections (Res. 11481, effective July 1, 2026), plus an $81 processing fee and state surcharges; design review for a non-66323 unit adds $400 (Director level).
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