Accessory Dwellings

Overview

ADU Central

What is an Accessory Dwelling Unit?

An Accessory Dwelling Unit (ADU), commonly known as a "granny flat" or "mother-in-law" unit, is a smaller home on your property. ADUs can be detached (stand-alone building) or attached (connected to your home), can be a small area in your home, or can be accomplished through a garage conversion. Regardless of the type, an ADU will always contain everything someone needs to live, including a kitchen, bathroom, and place to sleep.

ADUs are permitted in all residential zones and with additional requirements, office/commercial zones.

Please review the ADU FAQ page, or contact the Planning Department for more information.

What is an Accessory Dwelling Unit?

An Accessory Dwelling Unit (ADU), commonly known as a “granny flat” or “mother-in-law” unit, is a smaller home on your property. ADUs can be detached (stand-alone building) or attached (connected to your home), can be a small area in your home, or can be accomplished through a garage conversion. Regardless of the type, an ADU will always contain everything someone needs to live, including a kitchen, bathroom, and place to sleep.

ADUs are permitted in all residential zones and with additional requirements, office/commercial zones.

Please review the ADU FAQ page, or contact the Planning Department for more information.

Overview

ADU Development Standards

Zoning Regulations

Maximum Size (Floor Area) of an ADU

  • Detached: Detached ADUs cannot exceed a total of 1,200 square feet. If the unit is greater than 800 square feet, lot coverage must be
  • Attached: Attached ADUs may be up to 60% of the size of the primary dwelling, with a maximum size of 1,200 square feet. Regardless of the size of the primary home, an attached ADU with no more than 1 bedroom may be up to 850 square feet. An attached ADU with 2 or more bedrooms may be up to 1,000 square feet.

Lot Coverage

Lot coverage is the amount of your property that may be covered with structures. ADUs 800 square feet or less are exempt from lot coverage requirements and ADUs larger than 800 square feet must meet the lot coverage requirements. Allowed lot coverage ranges from 30% coverage to 50%, depending on the property’s zoning. To find out the zoning of your property, submit a zoning request online.

Setbacks (Distance From Property Line)

Structures are required to be located a certain distance from the property line. The required setback for an ADU is as follows:

  • Conversion of existing space: No additional setback is required if you are converting a legally built structure into an ADU.
  • Newly constructed detached unit: A minimum of 4-foot side yard and rear yard setback. Note: In some cases a setback may need to be larger than the minimum required due to easements for utilities, drainage, access, etc.
  • Attached ADU: A minimum of 5-foot side yard setback and a 20-foot rear yard setback. In some cases, the rear yard setback for attached units may be reduced to 10 feet. If your project requires a reduced rear yard setback, contact the Planning Division at (916) 625-5100 to see if your property qualifies.
  • If the ADU is proposed in the front of primary residence or along a street side of a property, the setbacks shall meet the requirements of the property’s zoning.

Maximum Height

The maximum height is 16 feet for a detached unit and 30 feet for an attached unit.

Parking

No additional parking is required for an ADU.

Density

ADUs are exempt from density calculations.

Overview

ADU FAQs

Accessory Dwelling Units (ADUs) and Junior Accessory Dwelling Units (JADUs) are independent and semi-independent dwelling units with complete or partial provisions for sleeping, cooking, and sanitation. ADUs and JADUs are allowed on properties with existing or proposed single-family dwellings. ADUs are also permitted on lots that are developed with an existing duplex or multi-family units, however JADUs are only allowed as part of a single-family dwelling. The City of Rocklin’s ADU Ordinance (Rocklin Municipal Code Chapter 17.67) was amended in accordance with the State of California law and became effective March 20, 2020. This resource provides guidance on frequently asked questions about Rocklin’s local ADU Ordinance. The California Department of Housing and Community Development’s ADU Handbook can be found here. 

ADU 101

What is an ADU? 

An ADU is a secondary unit with complete independent living facilities. An ADU may be created through the following methods: 

  • Building a new detached accessory building
  • Converting an existing legal accessory building or structure
  • Converting an existing legal accessory building or structure and adding an addition
  • Building an addition attached to a single-family dwelling unit. An ADU cannot be created by addition to a duplex or multifamily dwelling structure
  • Converting space in a single-family dwelling
  • Converting non-habitable portions in a multifamily dwelling structure
  • Junior ADU: Similar to a conversion ADU in that it is created from existing space within a single-family dwelling, but meets specific requirements and specifications for a Junior ADU prescribed by State law.

Where are ADUs allowed? 

ADUs are permitted on lots that are zoned to allow residential uses and where there is an existing or proposed residential use. 

Can I build an ADU on a lot with a duplex or an apartment building? 

Yes, the City’s ADU Ordinance allows ADUs on lots with duplexes and apartment buildings. In this FAQ and the ADU ordinance, we refer to these housing types as “multifamily buildings”.

Development Standards

How many ADUs are allowed on a lot? 

  • Lots with a Single-Family Dwelling: One (1) ADU and one (1) Junior ADU are allowed.
  • Lots with Multiple Detached Units: One (1) ADU or one (1) JADU.
  • Lots with Multifamily Development: On a lot with an existing duplex or multifamily building (3 units or more), one of the following is allowed:
    • A maximum of eight (8) detached ADUs are allowed on a lot with an existing multifamily building, not to exceed the number of existing units on the lot. 
    • Up to two detached ADUs are allowed on a lot that has a proposed multifamily dwelling.

Are ADUs subject to lot size requirements, coverage, and or density limitations?

No, any lot that is zoned residential and has an existing or proposed dwelling unit is eligible for an ADU. (See California Government Code Section 65852.2 and 65852.22) 

What is the maximum size of an ADU?

  • Detached/ attached new construction
    • 850 square feet (studio or one-bedroom)
    • 1,200 square feet (one-bedroom +)
  • Conversion ADU – May exceed size limitations. Note: An ADU created entirely through conversion with no modifications to the existing building envelope that exceeds the development standards for maximum size is allowed a physical addition of no more than 150 square feet for ingress and egress.
  • JADU – 500 square feet 

Where can a JADU be established?

A JADU may only be established within existing or proposed single family dwellings, which includes attached garages. If a JADU is established in an attached garage, parking replacement is not required.

What are the required setbacks for a new construction ADU or an addition to an existing accessory building or structure that will be converted into an ADU?

A newly constructed ADU or an addition to an accessory building or structure that will be converted into an ADU must maintain 4-foot side and rear setbacks, and must adhere to applicable zoning district requirements for the front setback. 

Can architectural features (e.g. Bay windows, eaves, electrical equipment, etc.) project into the required setbacks?

Eaves and heating and cooling equipment may project 3 feet into the required setback. (See RMC 17.08)

What is the maximum height allowed for new construction ADUs or a new addition that is part of an ADU?

The maximum height of an ADU varies slightly. For detached ADUs:

  • On a lot with an existing or proposed single- or multifamily unit, the maximum height is 16 feet.
  • On a lot with an existing or proposed single- or multifamily unit that is within a half mile of a major transit stop or high-quality transit corridor (as defined in Section 21155 of the Public Resources Code) an additional two feet in height shall be allowed, for a maximum height of 18 feet.
  • On a lot with an existing or proposed multifamily, multistory dwelling, the maximum height is 18 feet.

For Attached ADUs:

  • 25 feet or the height limitation that applies to the primary dwelling described in the Rocklin Zoning Ordinance, whichever is lower.

How is the maximum height of an ADU measured?

The maximum height of an ADU is measured from finished grade to the highest point of the structure.

How much floor area can be added to an existing accessory building or structure that will be converted into an ADU?

Additional floor area may be added to an existing accessory building or structure as long as the size of the overall ADU does not exceed the maximum size of limits outlined in question 7. An ADU created entirely through conversion with no modifications to the existing building envelope that exceeds the development standards for maximum size limits outlined in question 7 is allowed a physical addition of no more than 150 square feet to allow for ingress and egress. The addition must comply with maximum height and setback requirements. (See BMC 23.306.040) 

Can an ADU have a porch? Does the porch count in the allowed square footage for the unit?

Yes, ADUs may have a porch.

Maximum floor area allowed depends on the underlying zone. Contact the Planning Department for more information.

Can an internal connection be maintained between the primary dwelling unit and the ADU/ JADU?

Yes, an internal connection can exist between the respective units, provided the connection is fire rated and is secured. If a separate bathroom is not included in a JADU, an internal connection must be provided.

How do I legalize an existing unpermitted ADU?

Unpermitted ADUs will be reviewed and considered as a new construction ADU for zoning purposes and are subject to the existing development standards in the zoning ordinance.

Can a commercial space within a mixed- use structure be converted into an ADU?

No, an existing commercial space cannot be converted into an ADU. (See California Government Code Section 65852.2 and 65852.22.) 

Parking

Is replacement parking required for ADUs? 

Replacement parking for existing dwelling unit(s) is not required, but is allowed when a garage, carport, covered parking structure or designated uncovered parking area is physically replaced by an ADU.

Is parking required for new ADUs and JADUs?

No.

Rental and Ownership

Can I rent the primary dwelling unit(s) and ADU to different parties?

Yes, the primary dwelling unit and the ADU may be rented to different parties. (See California Government Code Section 65852.2 and 65852.22)

Does the property owner have to live onsite?

On a property with an ADU, there is no owner occupancy requirement. On a property with a JADU, the owner must live in the primary residence or the JADU. (See California Government Code Section 65852.2 and 65852.22) 

Can an ADU be used as a short-term rental?

No.

Is an ADU required to have its own address?

Yes. An address will be assigned to the ADU as part of the building permit process. However, JADUs are not required to have a separate address. (See California Government Code Section 65852.2 and 65852.22.) 

Can an ADU be sold separately from the primary dwelling unit?

Except as provided in Section 65852.26, the ADU may not be sold or otherwise conveyed separate from the primary residence. (See California Government Code Section 65852.2, 65852.22, and 65852.26)

Can non-habitable amenities of a multifamily dwelling structure (i.e. garage, laundry room, storage space) be converted into an ADU?

Yes, provided that the conversion of these spaces does not conflict with existing lease agreements and that the amenity space is associated with the residential units. (See California Government Code Section 65852.2 and 65852.22

Overview

Permit-Ready ADU Program

Logo header for Rocklin's Permit Ready Accessory Dwelling Unit. A graphic stylized house with the words PRADU under it.

In response to the current housing crisis in California and the AB 1332 Accessory Dwelling Unit (ADU) program requirement, the City of Rocklin has created the Permit-Ready ADU Program to increase affordable housing opportunities, and reduce permitting time and costs.   

The Permit-Ready ADU Program will make plans for different ADU types, styles, and sizes available to the public. Under this program, plans are designed by ADU builders, private licensed architects/engineers, and private designers to accommodate various site conditions. Plans are then reviewed by the Rocklin Building Department and are ready for permits. *

When an applicant selects one of the permit-ready construction plans provided (available plans will be posted once the plan check process is complete) and submits a project-specific site plan, City staff will review site-specific factors of the property, including compliance with the City Zoning Ordinance and California Energy Code requirements. Compliance with the current building code has been assured with the permit-ready plans, which result in a lower cost option for applicants and will reduce overall permitting time. However, homeowners who chose to use a permit-ready ADU plan are responsible for all other fees associated with the building permit. Please contact the City of Rocklin Building Department at building@rocklin.ca.us for a fee estimate.

Home owners are required to provide the following site-specific information when utilizing permit-ready ADU plans:

  • City of Rocklin building permit application
  • A complete and fully-dimensioned site plan. The ADU shall meet all zoning requirements – contact planner@rocklin.ca.us with questions.
  • Complete site-specific solar PV drawings

Permit-ready ADUs in the State Responsibility Area (SRA) shall meet all fire-resistance requirements of section 337 of the 2022 California Residential Code. Compliance may not necessarily be shown on the permit-ready plans.

Permit-ready ADUs in a FEMA Special Flood Hazard Area shall be elevated in accordance with section 322 of the 2022 California Residential Code. Compliance may not necessarily be shown on the permit-ready plans.

  • Apply online HERE. Once we receive a complete application utilizing permit-ready ADU plans we will approve or deny the application within 30 days.

*If the permit-ready plans have been modified using the available CAD files, the plans will need to be stamped and signed by a licensed design professional, as applicable. Additionally, the modified plans will not qualify for the Permit-ready ADU Program expedited review process. Plan review fees for modified ADU plans, or plans not included in the permit-ready ADU program, will be charged fees based on the project valuation.

Expedited permitting is not available to properties located in the Wildland Urban Interface, special flood hazard, or geologic hazard zones. Use the COMMUNITY MAP to find out if your property is in one of these areas.