Building an ADU in Rocklin

What you can build here

Rocklin's ADU rules are in Municipal Code Chapter 17.67, last amended by Ordinance 1206 (May 12, 2026). ADUs and junior ADUs (JADUs) are "a permitted use in all zones where residences are a permitted or conditional use." The code says that where it conflicts with state law, "the applicable provision of state law shall control."

An ADU can be attached to the house, inside the house, inside an existing accessory building, or detached. It needs a full kitchen with a stove, range or cooktop; the code says "microwaves and ovens cannot replace the stove." Your zone's other development standards apply unless the ADU chapter says otherwise.

How many. The code says "one accessory dwelling unit may be allowed per residential lot" with a single-family home, plus a JADU. State law requires every city to approve, on a single-family lot, one ADU converted from existing space, one JADU and one new detached ADU of up to 800 sq ft with 4 ft side and rear setbacks. If you want all three, ask the Community Development Department how the city applies state law to your lot.

Apartment lots: you can convert non-living space in an existing multifamily building into at least one ADU and up to 25% of the units, and build up to eight detached ADUs (18 ft tall, 4 ft side and rear setbacks) as long as the existing units stay. State law also caps those detached ADUs at the number of existing units and allows two detached ADUs with a proposed apartment building.

SB 9 lots: a lot created by an SB 9 lot split can have no more than two units in total, counting ADUs and JADUs, and the original parcel no more than four. See our California page and SB 9 lot split guide. [1][2]

Size, height and setbacks

• Size: up to 1,200 sq ft of interior livable space, attached or detached. An attached ADU is also limited to 50% of the existing house, but the city must allow at least 850 sq ft, or 1,000 sq ft with more than one bedroom. The minimum is the size of an efficiency unit.
• Height, detached: 16 ft from natural grade. Within a half-mile of a major transit stop or high-quality transit corridor, 18 ft plus 2 ft to match the house's roof pitch. On a lot with a multistory apartment building, 18 ft.
• Height, attached: 25 ft or the height of the house, whichever is lower.
• Setbacks: 4 ft from side and rear lines; other setbacks follow your zone. None are needed to convert existing space or rebuild a structure in the same place and size.
• Front setback: the code allows an ADU in the front setback only if it is "physically or legally impossible" to build it elsewhere, documented in your application. State law says front setbacks can't block an ADU of at least 800 sq ft with 4 ft side and rear setbacks. Confirm with the Community Development Department if your lot has no other room.
• Lot coverage: ADUs are exempt from lot coverage limits "to the minimum extent necessary" to build one.

Entrance. The ADU needs its own entrance. On a corner lot it can't face the same street as the house's entrance. On a lot with one street frontage, it may face the street only if a side or rear entry is blocked by a lack of a 4 ft clear path, a slope over 15%, or a recorded easement.

Design. The ADU must match the house: roof pitch within 2 degrees, the same roof material type, the same main siding type (or better), consistent window trim, sill height and proportions, and eaves within 12 inches of the house's depth. No balcony, deck or open stair landing may face the nearest side or rear line, except for getting in and out. City pre-approved plans are exempt from design standards that conflict with the approved design. [1][2]

Parking

The code requires "one parking space per accessory dwelling unit," in addition to the house's parking. It can be tandem on a driveway or in setback areas unless the Community Development Director finds that isn't feasible because of topography or safety. No parking may extend into a public sidewalk or right-of-way.

No parking is required when the ADU:

• is inside the existing or proposed house or an existing accessory building,
• is within a half-mile walk of public transit (a bus stop or train station on a fixed route),
• is in an architecturally and historically significant district,
• is where on-street parking permits are required but not offered to its occupants, or
• has a car share parking area within one block.

You don't have to replace a garage, carport or parking space you demolish or convert for the ADU. JADUs need no parking at all.

State law adds more exemptions. State guidance says no parking can be required for an ADU applied for together with a new home on the same lot if the ADU or the lot also meets one of the exemptions above, and none for ADUs built under the state's streamlined rules ("66323 Units"), such as a new detached ADU of up to 800 sq ft with 4 ft side and rear setbacks. Rocklin's code doesn't list these but says state law controls where the two conflict; confirm with the Community Development Department. [1][2]

Fees and utilities

ADU and JADU applications pay an application fee, plus building inspection and permit fees.

Impact fees. The code says "no impact fees may be imposed" on an ADU of 750 sq ft or less of interior livable space, or a JADU of 500 sq ft or less. Larger ADUs pay impact fees "proportionately in relation to the square footage of the primary dwelling unit." State guidance says ADUs under 500 sq ft are not subject to school impact fees.

Utilities. A new ADU may be required to have its own utility connection, including a separate sewer lateral, with a connection fee in proportion to its size or plumbing fixtures, and "separate electric and water meters shall be required." JADUs and ADUs converted from interior space are exempt from separate connections and their fees, unless built within a new house. All utility extensions must be underground, and no ADU is permitted if water or sewer service is inadequate.

Ask the city for a fee estimate for your project. See our ADU cost and ADU financing guides. [1][2]

How long it takes

The code says the city processes a complete ADU or JADU application "within sixty calendar days" and approves it if it meets the chapter. If your application is incomplete, the city returns it within 15 business days with a single written list of what's missing. If you use a city pre-approved ADU plan, the city processes it within 30 calendar days.

If you apply together with a new single-family home, the ADU isn't acted on until the home is approved, then within 60 days after that, and no one may live in the ADU until the city approves occupancy of the home. You can ask the city to delay processing. See our ADU permit process guide. [1]

Garage conversions and junior ADUs

You can convert a garage or other existing accessory building into an ADU with no new setback and no replacement parking. See our garage conversion guide. Fire sprinklers aren't required in an ADU or JADU if the house doesn't need them.

A junior ADU must be inside a single-family home, up to 500 sq ft, with at least an efficiency kitchen (a real cooking appliance, a sink with hot and cold water, a refrigerator, and counter and storage space). It can have its own bathroom or share the house's. You can add up to 150 sq ft only for getting in and out. Its entrance can't face the same street as the house's front door unless the site makes that impossible. A second-story JADU's exterior stair may reduce the house's side or rear setback to 4 ft, and elevated decks or landings within 10 ft of a side or rear line need a 6 ft opaque screen.

Before the building permit, you record a covenant (in a form set by the city attorney) and file a copy with the Community Development Department. It bars selling the JADU separately and renting for fewer than 30 consecutive days.

Owner occupancy. The code says the owner must live in the house or the JADU "except if a junior accessory unit contains independent sanitation facilities." Other parts of the same section, and the covenant, require an owner to live on the lot without that exception. State law requires owner occupancy only when the JADU shares a bathroom with the house; confirm with the Community Development Department. See our junior ADU guide. [1][2]

Renting out your ADU

ADUs and JADUs "may be rented independently of the primary unit," but not "for fewer than thirty consecutive calendar days." The code says "no owner-occupied requirement shall be imposed for any accessory dwelling." An ADU can't be sold separately from the house "except as otherwise allowed by California law."

Older ADUs. Until January 1, 2030, the owner of an ADU built before January 1, 2020 can ask the building official to delay correcting building-standard violations for five years. The city grants it if enforcement isn't needed for health and safety, but not for structural, fire or other life-safety problems. An ADU may raise your property taxes; see our ADU property tax guide. [1]

Permit steps in Rocklin

1. Check your zone and the ADU rules

   Read Chapter 17.67 and confirm your zone's setbacks and which ADU combination fits your lot with the Community Development Department. [1]

2. Choose a design

   Use a city pre-approved ADU plan (faster review) or have plans drawn that meet the size, height, setback, entrance and design standards. [1]

3. Apply and pay the application fee

   Submit the ADU or JADU application with the application fee. Incomplete applications come back within 15 business days with a list of what's missing. [1]

4. Record the JADU covenant (JADUs only)

   Record the city attorney's covenant and file a copy with the Community Development Department before the building permit is issued. [1]

5. Get the decision and building permit

   The city acts within 60 calendar days of a complete application (30 with a pre-approved plan). Pay building inspection and permit fees, and any impact or utility fees that apply. [1]

6. Build and pass inspections

   Build to the approved plans, with utility extensions underground, and pass the city's building inspections. [1]

Who to call

• Community Development Department

  ADU and JADU applications, zoning, covenants and building permits

  [1]

Questions people ask