Sacramento ADU rules and permits, by jurisdiction

Sacramento has four different answers to “can I build an ADU, and how big?” Which one applies depends on which side of a city line your house sits on. That’s worth settling before you spend money on drawings.

First: which jurisdiction are you actually in?

This is not a ZIP-code question. Much of what people call Carmichael or Fair Oaks is unincorporated Sacramento County, which means the County’s building department reviews your plans, not the City of Sacramento’s. Folsom and Rancho Cordova each run their own. Neighbouring houses can occasionally fall under different authorities.

Get this wrong and you submit to the wrong counter, which costs you weeks. The assessor’s parcel record settles it in a few minutes.

What’s the same everywhere in California

Some of the most consequential rules are state law and don’t vary by jurisdiction:

• The 60-day clock. An agency must approve or deny a complete ADU application within 60 days or it is deemed approved. Since January 2026 there’s also a 15-business-day completeness determination.
• Review is ministerial. No public hearing, no CEQA review, no discretionary appeal. Your neighbours do not get a vote.
• Four-foot side and rear setbacks are the most any agency may require for a new detached ADU.
• No owner-occupancy requirement for ADUs. An agency cannot make you live on site.
• Impact fees are waived on an ADU of 750 sq ft or less of interior livable space, and a JADU of 500 sq ft or less.
• Utility connection fees can’t treat an ADU as a brand-new residential use.

If a contractor or a local handout tells you otherwise on one of these, check the date on their source. This area of law changed on January 1 2025 and again on January 1 2026.

The two tracks: the thing most people don’t know they can choose

In the City of Sacramento, and in a similar form elsewhere, there are effectively two ways to get an ADU approved, and they buy different things.

The local track is the city’s own ordinance. In Sacramento that allows a detached ADU up to 1,200 sq ft, considerably larger than the state minimum. It also permits two ADUs on a single-family lot (or one ADU plus one JADU). If you want size, this is the track.

The state track (often called the “66323” track) is the floor every agency must allow regardless of local rules: roughly 800 sq ft, four-foot setbacks, and a height allowance that can’t be zoned away. If your lot is tight or your local standards would otherwise block you, this track exists precisely so it can’t.

The trade-off that usually decides it: under Sacramento’s local track an ADU may be rented for terms under 30 days, subject to the city’s short-term rental rules. Under the state track it may not be. That’s written into state law. If short-term rental is part of your plan, this determines your track, and therefore your design.

Two more City of Sacramento specifics worth knowing: there is no minimum off-street parking requirement anywhere in the city for any land use, following a 2025 ordinance, so the usual ADU parking argument simply doesn’t arise. And ADUs occupying less than 800 sq ft of lot coverage are exempt from maximum lot coverage and minimum open-space rules.

How the four jurisdictions actually differ

Every figure below was checked against the jurisdiction’s own code or official handout in August 2026. Where a rule is state law it’s the same everywhere, so it isn’t in this table. See the section above.

	City of Sacramento	Sacramento County (unincorporated)	Folsom	Rancho Cordova
Detached ADU, max size	1,200 sq ft	1,200 sq ft	850 sq ft (1 bed) / 1,000 sq ft (2+ beds)	850 sq ft (studio or 1 bed) / 1,000 sq ft (more)
Detached ADU, max height	The underlying zone’s limit, 35 ft in R-1	16 ft; 18 ft near a major transit stop or to align the roof pitch	25 ft, or the height of the house, whichever is less	16 ft; 18 ft within a half-mile of a major transit stop
Attached ADU, max size	Greater of 50% of the primary dwelling or 850 sq ft	Greater of 50% of habitable area, or 850 / 1,000 sq ft by bedroom count, but never larger than the primary dwelling	850 / 1,000 sq ft by bedroom count	850 / 1,000 sq ft by bedroom count
JADU, max size	500 sq ft	500 sq ft	500 sq ft	500 sq ft
Parking	None: the city has no minimum off-street parking for any use	One space, but the exemptions are broad enough that most new detached ADUs need none	One per ADU or per bedroom, whichever is less, with six exemptions	One per ADU or per bedroom, whichever is less, with six exemptions
Free pre-approved plans	Yes: three Shelf Ready plans (studio, 1-bed, 2-bed)	Yes: five Shelf Ready plan sets, 460–1,184 sq ft	Program exists, but no plans published yet	None published

A few things this table can’t carry, and they matter:

• The County’s parking row is easy to misread. The rule says one space, then lists exemptions that include any new detached ADU of 800 sq ft or less, and any ADU accessory to a multifamily dwelling. In practice most new detached ADUs land inside an exemption. Don’t budget a parking space until someone has checked which exemption applies to you.
• Folsom’s six-foot separation between a detached ADU and the house applies only to units on its local track. Units built under the state track aren’t subject to it.
• “Free” pre-approved plans means the drawings are free, not the project. Standard building permit fees, a site plan you supply, separate fire-district review and impact fees above the size threshold all still apply. Note too that both Shelf Ready programs were drawn to the 2022 code cycle, and California moved to the 2025 cycle on January 1 2026. It is worth confirming they’ve been updated before relying on the 30-day fast track.

ADU, JADU, or garage conversion?

Three different things, three rule sets, three very different budgets.

A detached ADU is a separate structure: its own walls, roof, foundation, kitchen and bathroom. Most expensive per square foot, because you’re building a small house and running utilities to it.

An attached ADU shares at least one wall with the main house. Usually cheaper: you inherit some structure and the utility runs are shorter.

A JADU is carved out of the existing house, most often a converted bedroom with its own entrance. Capped at 500 sq ft, must be within the walls of the existing dwelling, and needs at minimum an efficiency kitchen. Cheapest path, but it takes a room away from the main house.

A garage conversion is the most common starting point, because the structure, slab and roof already exist. Be aware that jurisdictions treat it as a change of use: the structure has to be brought up to current residential standards, so it’s foundation, framing, egress, insulation and energy compliance, not just drywall and a window.

Utilities are where budgets actually move

The part homeowners rarely price in: a detached ADU often needs its own electrical service, and sometimes its own water and sewer connections. Trenching across a finished yard, an upgraded main panel, or a sewer lateral that has to reach the street can each move the number meaningfully. None of it appears in the renderings.

In older Sacramento-area neighborhoods there’s a second trap: mature trees. Sacramento County’s tree ordinance regulates trenching and grading inside a protected tree’s dripline, not just removal. That dripline is often exactly where the new utility run wants to go.

Ask any contractor how they’ve scoped utilities specifically, and whether it’s inside their price or excluded. It’s the most common exclusion we see in other firms’ proposals.

What to do before you call anyone

1. Confirm your jurisdiction. The assessor’s parcel record settles it.
2. Find your lot lines and setbacks. They determine whether a detached ADU fits at all.
3. Locate your sewer lateral and electrical panel. Their position and capacity shape cost more than finishes will.
4. Decide what the ADU is for. Family, long-term rental and short-term rental are three different briefs. In Sacramento the third one changes which approval track you can use.
5. Check whether a free pre-approved plan fits. If it does, it’s cheaper and faster, and state law shortens the approval window to 30 days.