Add an ADU to your Folsom home

LotUpside is a one-stop ADU company for homes in the City of Folsom: we check your lot free against the city's rules, then match you with licensed designers and builders and coordinate the project with them.

Check your lot · free

What the Folsom rules allow on your lot: setbacks, the biggest unit that fits, fees.

Design your ADU · free

Shape it in live 3D: size, rooms, roof and finishes, with an estimate priced for Folsom.

Start designing

ADU rules at a glance

Largest detached ADU (City rules)Local rule: 850 sq ft (1,000 sq ft with 2+ bedrooms)Folsom Municipal Code 17.105.150(B)(2)
Detached ADU, state-law pathState law: Up to 800 sq ftGov. Code 66323(a)(2) and 66321(b)(3); Folsom Municipal Code 17.105.150(A)(1)
Height, state-law detached ADUState law: 16 ftGov. Code 66321(b)(4); Folsom Municipal Code 17.105.150(A)(1)(d)
Side and rear setbacksLocal rule: 4 ftFolsom Municipal Code 17.105.150(A)(1)(c) and (B)(3)
Placement, City-rules detached ADULocal rule: Behind the front of the house, 6 ft from other buildingsFolsom Municipal Code 17.105.150(B)(3)
ADUs per single-family lotLocal rule: Up to 3 ADUs (one of each type) + 1 junior ADUFolsom Municipal Code 17.105.120(A)(1)
Impact feesLocal rule: None up to 750 sq ftFolsom Municipal Code 17.105.060(C)(2); Gov. Code 66311.5(c)(1)
School feesState law: None under 500 sq ftGov. Code 66311.5(c)(3); Education Code 17620
Parking for a City-rules ADULocal rule: At most 1 space, with exceptions; no replacement parkingFolsom Municipal Code 17.105.180
Owner living on siteState law: Not for an ADU; yes for a junior ADU that shares a bathroomGov. Code 66315 and 66333(b); Folsom Municipal Code 17.105.160(B)(4)
Permit decisionState law: Within 60 days of a complete applicationGov. Code 66317(a)(3); Folsom Municipal Code 17.105.050(A)(2)
City pre-reviewed plansLocal rule: City ADU Master Plan program (plans to be listed on the City's page)City of Folsom, ADU Master Plan Options page
SewerLocal rule: Public sewer; septic only where the City allows itFolsom Municipal Code 17.105.130(B) and (C)
Planning deskLocal rule: PlanningEPC@folsom.ca.us, 916-461-6202City of Folsom Planning Division, ADU page

Last verified 2026-10-15. Rules change; the City of Folsom planning desk has the final word (916-461-6202).

What's different in Folsom

850 sq ft under City rules, 800 sq ft under state law

Folsom rewrote its ADU chapter with Ordinance 1361, in effect since May 14, 2026. A detached ADU built to City rules can reach 850 sq ft as a studio or one-bedroom, or 1,000 sq ft with two or more bedrooms, up to 25 ft tall or the height of the house, whichever is less; it sits behind the front of the house, 6 ft from other buildings, and goes through the City's design review. A new detached unit of up to 800 sq ft with 4 ft side and rear setbacks follows state law instead and is exempt from the City's design standards. A single-family lot can combine up to 3 ADUs, one of each type, plus a junior ADU. LotUpside's free check fits the 800 sq ft state-law unit.

Folsom Municipal Code 17.105.090, 17.105.120 and 17.105.150 (Ordinance 1361)

Hillside lots: a grading step, not a ban

Parts of Folsom are mapped hillside areas under Code Chapter 14.33, which sets grading and design standards there: an engineered grading plan is needed when cut and fill exceed 500 cubic yards or a protected tree has to come out, while a residential lot under an acre in a built subdivision can be exempt from its grading permit. The chapter's 20% slope limit applies to creating new lots, not to adding an ADU on an existing one. On a steep lot, LotUpside's check lists the slope as a step for grading review, not a stop.

Folsom Municipal Code Chapter 14.33 (14.33.150, 14.33.180)

Planned developments, specific plans and the Historic District

Parts of Folsom sit in a planned development (PD) or a specific plan area, such as the Folsom Plan Area, and those can set their own development standards: a PD permit may modify the zoning standards, and a specific plan prevails over the zoning code where the two conflict. In the Historic District, ADUs built to City rules follow added historic design standards (Code 17.105.200), and the City asks owners there to contact the Planning Division for its supplemental requirements. LotUpside's check can't read those standards, so on these lots the planning desk (PlanningEPC@folsom.ca.us, 916-461-6202) confirms what applies.

City of Folsom ADU page; Folsom Municipal Code 17.37.010, 17.38.030 and 17.105.200

Estimated costs and rents in Folsom

Type	Est. all-in cost	Est. rent
Detached 2 bedroom	$193,000-$289,000	$1,925-$2,375/mo
Detached 3 bedroom	$224,000-$341,000	$2,425-$2,975/mo

Estimates for a first conversation, not bids or appraisals. Source: LotUpside price book sac-2026-10. Provisional estimate: rent, build-cost and value figures are our Sacramento-area estimates, not yet researched for Folsom. They are not Folsom quotes, bids or appraisals. Garage conversions and junior ADUs aren't in this table for Folsom: the check can't verify them there yet, so a report lists them as not verified.

How we work in Folsom

1
Free lot check
A 12-check property screening from public records: what fits on your lot and what it adds.
2
Get matched with a licensed designer
Ask for a free consult and we look for a licensed designer for your plans and permit.
3
Get matched with a licensed builder
The builder holds the construction contract; we coordinate the project with them.

Licensed partners design and build, and the builder holds the construction contract. Partners are signed in some areas so far. All figures are estimates, not bids.

What our check reads in Folsom

Rules from Folsom ADU standards (Code Chapter 17.105); CA Gov. Code 66323; zoning from the City of Folsom zoning map and Code Chapter 17.105. Plus county parcel and assessor maps, CAL FIRE fire zones, FEMA flood maps, the California Geological Survey, the USDA soil survey, USGS elevation and Microsoft building outlines.

In Folsom the check fits the state-law path (800 sq ft) and stops at 'needs a closer look'; planned-development, specific-plan and historic lots are confirmed with the planning desk. Rents and build costs are Sacramento-area estimates, labelled provisional.

Folsom ADU questions answered

Floor plans to start from

Measured ADU layouts you can edit and download as CAD files, then check against the Folsom rules above.

Ready to build in Folsom?

We'll match you with a licensed designer and builder in your area and coordinate the project. Free consult, no obligation.

Want to build it?

We'll match you with a licensed designer and builder in your area and coordinate the project. Free consult, no obligation.

Licensed partner designers and builders do the design and construction, and the builder holds the construction contract. Partners are signed in some areas so far; elsewhere we'll tell you plainly what we can do.

Folsom ADU questions

How big can a detached ADU be in Folsom?

Under Folsom Municipal Code 17.105.150, a detached ADU built to City rules can be up to 850 sq ft as a studio or one-bedroom, or 1,000 sq ft with two or more bedrooms, and up to 25 ft tall or the height of the house, whichever is less. A new detached ADU of up to 800 sq ft with 4 ft side and rear setbacks follows state law instead (Gov. Code 66323), with a 16 ft height limit in most cases and no City design standards.

Can I use a Folsom ADU as a short-term rental?

No. Folsom Municipal Code 17.105.070 allows an ADU or junior ADU to be rented only for terms of 30 days or longer, and the City's ADU page says ADUs can't be used as vacation rentals. State law (Gov. Code 66323 and 66333) asks for terms longer than 30 days for state-law ADUs and junior ADUs.

What school fees does a Folsom ADU pay?

State law (Gov. Code 66311.5) keeps an ADU under 500 sq ft free of school fees; the district's own page lists ADUs of '500 square feet or less' as excluded, so check a unit of exactly 500 sq ft with the district. For a larger unit, Folsom Cordova Unified School District lists a residential rate of $10.26 per sq ft for Folsom, effective April 16, 2026, paid to the district before the City issues the building permit.

Do I have to add parking for an ADU in Folsom?

Often not: Folsom Municipal Code 17.105.180 waives it within half a mile walking distance of public transit, in the Historic District, for an ADU inside the house or an existing accessory building, and with a car share within one block, and parking lost when a garage is converted or removed never has to be replaced. Otherwise a City-rules ADU needs one space per ADU or per bedroom, whichever is less. State law (Gov. Code 66323(b)) limits the standards a city can impose on the 800 sq ft state-law unit, but the City's Detached ADU Checklist still asks for a space unless an exception applies, so confirm with the planning desk.

How close to the property line can a Folsom ADU go?

Four feet from the side and rear lot lines under Folsom Municipal Code 17.105.150, the same as state law. The City's ADU Design Workbook notes that a unit less than 5 ft from a property line triggers extra building code requirements, which can raise construction cost.

What's free, and what's in the $49 full report?

The free check gives the verdict from a 12-check property screening, your best move with the value it adds, the monthly rent and the cash you put in. The full report adds every option ranked, cost vs value ranges, concept floor layouts and site plan drafts, and every check with its sources. It is a one-time payment per property.

Is this a permit, or a plan I can build from?

Neither. It is a screening from public records, not professional advice, and not a survey, soils report, appraisal, loan offer or permit; every number is an estimate. A licensed designer confirms the final plan, and your city or county gives final approval.