Accessory Dwelling Units

Accessory Dwelling Units (“ADU”) have been known by many names over the years: granny flats, second units, in-law units, backyard cottages, and more. ADUs are an innovative, affordable, and effective option for adding much-needed housing in California.

Click on the tabs above for more general information about the different types of ADUs. View the Accessory Dwelling Unit Handbook (at right) for more detailed information about ADU size and height limits, setback requirements, parking requirements or exemptions, and other design regulations. 

About an ADU

ADUs provide independent living quarters for one household on the same lot as the primary single-family dwelling. The ADU provides full facilities for sleeping, eating, cooking, and sanitation. The ADU may be detached, attached, or a converted structure located within the living areas of the primary dwelling unit on the lot.

• Detached: the ADU structure is detached from the primary dwelling unit.
• Attached: the ADU structure is attached to the primary dwelling unit.
• Converted: the ADU within the existing primary dwelling unit or the ADU was established through the conversion of an accessory structure, for example, a garage or pool house.
• Junior ADU: the ADU is within the existing walls of the single-family residence, and there is a size limit of 500 square-feet.

Knowing what type of ADU you want to build is important because there are different requirements and development standards for the various types of ADUs. Read more about the requirements on this webpage by clicking on the tabs above. 

Junior ADUs

A Junior ADU may be created on a lot zoned for single-family residences with one primary dwelling. The requirements for Junior ADUs include the following:

• May be created within the walls of the proposed or existing single-family residence, including attached garages (as attached garages are considered within the walls of the existing single-family residence).
• Junior ADU is not allowed in accessory structures (the creation of a Junior ADU must be within the single-family residence).
• Junior ADU shall contain no more than 500 square-feet.
• Junior ADU created in the attached garage are not subject to the same parking protections as ADUs, and could be required by the local agency to provide replacement parking.
• Junior ADUs are limited to one (1) per residential lot with a single-family residence (lots with multiple detached single-family dwellings are not eligible to have Junior ADUs).
• They may share central systems, contain a basic kitchen utilizing small plug-in appliances, may share a bathroom with the primary dwelling.
• Create no additional stress on utility services or infrastructure because they simply re-purpose existing space within the residence and do not expand the dwelling’s occupancy.

Click on the ‘General Requirements’ tab above for a brief overview of development standards and parking requirements for Junior ADUs.

Click on the Accessory Dwelling Unit Handbook (at right) for more detailed information about height limits, setback requirements, parking requirements or exemptions, and other design regulations. 

2024 State Law Update

Senate Bill (SB) 477 went into effect in March 2024, and made State ADU law easier to read and navigate. SB 477 relocated numerous Government Code sections pertaining to ADUs (e.g., 65852.2, 65852.22, 65852.26) into a new chapter, and key regulations are now divided into smaller sections by topic area. The changes to state law are only organizational (not substantive). 

SB 477 added a new Chapter 13 to Division 1 of Title 7 of the Government Code. The new Chapter 13 is divided into four articles, and each article is further divided into various sections as follows:

• Article 1 – General Provisions. Now provided in Gov. Code sections 66310, 66311, 66312, and 66313. 
• Article 2 – ADU Approvals. Now provided in Gov. Code sections 66314 through 66332.
• Article 3 – Junior ADUs. Now provided in Gov. Code sections 66333 through 66339.
• Article 4 – ADU Sales. Now provided in Gov. Code sections 66341 and 66342.

In addition, Senate Bill (SB) 1211 was signed into State law on September 19, 2024. 

What are the benefits of ADUs?

• Affordability: ADUs are an affordable type of home to construct in California because they do not require paying for land, major new infrastructure, structured parking, or elevators.
   
• Efficiency: ADUs can provide as much living space as many newly-built apartments and condominiums, and they’re suited well for couples, small families, friends, young people, and seniors.
   
• Cost-Effective: ADUs are built with cost-effective wood frame construction, which is significantly less costly than homes in new multifamily infill buildings. ADUs also use less energy and resources (electricity, water, etc.) than larger full-size homes. 
   
• Income: ADUs can provide a source of income for homeowners. ADUs can also increase the property value. 
   
• Flexibility: ADUs give homeowners the flexibility to share independent living areas with family members and others, allowing seniors to age in place as they require more care.
   
• Privacy: ADUs allow extended families to be near one another while maintaining privacy.
   
• Housing options: ADUs provide a method to build more housing quickly, within existing neighborhoods while preserving neighborhood character, and without increasing density. Building a new ADU usually takes a few months, as opposed to a new housing subdivision that could take two years or more. 

Different Types of ADUs

A) Detached ADUs

B) Attached ADUs

C) ADUs above a garage

D) Junior ADU

General Requirements

The following list is provided as an overview of the general requirements in State ADU law, but may not list all applicable regulations for your particular project.

Please read and review the Accessory Dwelling Unit Handbook provided by HCD – see link to PDF document at right. 

Number of ADUs per lot:

Single-Family Residential Lots:

• One (1) detached ADU on a lot with an existing or proposed single-family dwelling;
• One (1) Junior ADU, within an existing or proposed single-family dwelling; and,
• One (1) ADU converted from existing space (such as a garage).
• See Gov. Code Section 66323 or the ADU Handbook (by HCD) for more information. 
• The space must have exterior access from the existing or proposed single-family dwelling. 
• The side and rear setbacks must be sufficient for life safety. 

Multi-Family Residential Lots:

• On a lot with a proposed multifamily dwelling: up to two (2) detached ADUs.
• On a lot with an existing multifamily dwelling: up to eight (8) detached ADUs. However, the number of ADUs shall not exceed the number of existing units on the lot.
• At least one (1) ADU within an existing multifamily dwelling, up to 25% of the existing number of multifamily units. All interior ADUs, however, must be converted from non-livable space (such as storage rooms, boiler rooms, passageways, attics, basements, or garages).
• A Junior ADU cannot be constructed on a multifamily site concurrently with an ADU.
• A lot where there are currently multiple detached single-family dwellings is eligible for creation of one ADU per lot by converting space within the proposed or existing space of a single-family dwelling or existing structure, and by building a new detached ADU.

Maximum ADU Size

Detached ADU: 1,200 square-feet maximum.

Attached ADU: up to 50% of the floor area of the existing primary dwelling, and at least 800 square-feet minimum. 

• ADUs are allowed to add up to 150 square feet beyond the physical dimensions of the existing accessory structure to provide for ingress/egress.

Junior ADU: 500 square-feet maximum.

• Junior ADU is required to be created within the existing walls of the single-family residence (or attached garage).
• Junior ADU is not allowed to add up to 150 square-feet beyond the physical dimensions of the existing primary unit or structure.

Setbacks for ADUs:

Front yard: 25 feet minimum in most single-family residential districts (R-1, R-E, R-S, R-A, R-A-A, R-R, R-R-A, A-1 and A-2) and specific plans. To verify the required yards and setbacks for residential Specific Plan areas, please refer to the Specific Plans webpage (click here).  Front setbacks may vary for corner lots, key lots, reverse corner lots, etc. (please refer to the zoning district standards listed in RMC Title 18 – Zoning Regulations).

Side yard: 4 feet minimum & maximum (applicant may choose to provide a larger setback)

Rear yard: 4 feet minimum & maximum (applicant may choose to provide a larger setback)

Converting an existing structure to ADU:

• A local agency may allow the expansion of a detached structure being converted into an ADU when the existing structure does not have four-foot rear and side setbacks.
• A local agency may allow the expansion area of a detached structure being converted into an ADU to have no setbacks, or setbacks of less than four feet, if the existing structure has no setbacks, or has setbacks of less than four feet.
• A local agency shall not require setbacks of more than four feet for the expanded area of a detached structure being converted into an ADU.

Permitted projections into yards (see RMC 18.152.070):

• Open, unenclosed, covered patios may project to within five feet (5′) of the rear property line.
• Open, unenclosed stairways or balconies may extend into a rear yard not more than four feet (4′), and into a front yard not more than thirty inches (30″).
• Open, unenclosed porches, platforms or landing platforms which do not extend above the level of the first floor of the building may extend or project into the front or rear yard a distance of not more than six feet (6′).
• Roof projections may extend into a required side yard, but not closer than two feet (2′) to the side property line, nor creating less than four feet (4′) of space between such projection and the closest point on any adjoining building.
• No permitted projection shall be located closer than ten feet (10′) from any existing or potential structure on abutting residential properties.
• Other exceptions to yards and setbacks: see RMC Section 18.152.070.

Other considerations for setbacks:

• Setbacks may also account for utility easements or recorded setbacks.
• The California Building Code may also have other (more stringent) building separation and/or design requirements. Please consult a licensed architect or other qualified design professional if you have any questions about Building Code regulations. 

Definitions in the Zoning Code:

• “Front Yard” – see RMC 18.08.585
• “Rear Yard” – see RMC 18.08.590
• “Side Yard” – see RMC 18.08.595
• “Frontage” or “Front Lot Line” - see RMC 18.08.260

ADU Height Limit:

Detached ADU:

• No less than 16 feet (minimum) for a detached ADU on a lot with an existing or proposed single-family or multifamily dwelling unit. 
• No less than 18 feet (minimum) for a detached ADU on a lot with an existing or proposed single-family or multifamily dwelling unit that is within one-half mile walking distance of a major transit stop (e.g., train station). An additional two feet (up to 20 feet) shall be allowed to accommodate a roof pitch on the ADU that is aligned with the roof pitch of the primary unit. 
• No less than 18 feet (minimum) for a detached ADU on a lot with an existing or proposed multifamily, multistory dwelling unit.

Attached ADU:

• A height of 25 feet (maximum) or the height limitation in the local zoning ordinance that applies to the primary dwelling, whichever is lower, for an ADU that is attached to a primary dwelling. 

Other zoning regulations:

Maximum of 2-1/2 stories and 35 feet in most single-family residential districts (R-1, R-E, R-S, R-A, R-A-A, R-R, R-R-A, A-1 and A-2) and the R-2 district. Please refer to the height limits for the subject property listed in RMC Title 18 – Zoning Regulations.

Definitions in the Redlands Municipal Code:  “Building Height” – see RMC 18.08.115

Parking for ADUs:

One (1) parking space per unit or bedroom, whichever is less.

• These spaces may be provided as tandem parking on a driveway (tandem parking means two or more automobiles that are parked on a driveway or in any other location on a lot, lined up behind one another).
• When a garage, carport, or covered parking structure is demolished in conjunction with the construction of an ADU, or converted to an ADU, the local agency shall not require that those off-street parking spaces for the primary unit be replaced.
• Off-street parking spaces for the ADU shall be permitted in setback areas in locations determined by the local agency, or through tandem parking, unless specific findings are made (specific findings must be based on specific site or regional topographical or fire and life safety conditions).
• Guest parking spaces shall not be required for ADUs.
   
• The following are exempt from ADU parking requirements (no parking required):

a) ADU is located within one-half mile walking distance of public transit (click on the following links to view Omnitrans bus route maps: Route 8, Route 15, Route 19).
b) ADU is located within an architecturally and historically significant historic district.
c) ADU is part of the proposed or existing primary residence or an accessory structure.
d) When on-street parking permits are required but not offered to the occupant of the ADU.
e) When there is a car share vehicle located within one block of the ADU.

Definitions in the Redlands Municipal Code:

• Covered parking spaces: not less than 10′0″ in width and 20′0″ in length – see RMC 18.164.110(A)
• Uncovered parking spaces: not less than 9′0″ in width and 19′0″ in length – see RMC 18.164.110(B)
• Access to street – see RMC 18.164.120

Garages and ADUs: ADUs may be constructed within an existing garage (i.e., garage conversion). Also, an ADU that is detached from the proposed or existing primary dwelling may include a new detached garage.

Lot Coverage or Open Space: If development standards such as lot coverage, floor area, or open space requirements might limit the development of an ADU, then the intent of State law is to preclude local zoning regulations so that State law promotes the construction of more ADUs. Local governments may continue to enforce building standards (e.g., California Building Code), health and safety standards, and may also consider design, landscape, and other standards to facilitate compatibility.

Bedrooms:  No limit (minimum or maximum) on the number of bedrooms of an ADU. 

Kitchen & Bathroom:

ADUs (attached and detached) must have their own independent living facilities, which is to include a small kitchen or cooking area as well as lavatory facilities. No passageway shall be required in conjunction with the construction of an ADU.

Junior ADUs may have their own kitchen and lavatory, but they are not required to have their own separate kitchen and lavatory facilities inside the Junior ADU. However, if a kitchen and lavatory are not provided within the Junior ADU, then interior access must be provided to the portions of the single-family residence that do provide the kitchen and bathroom facilities.

Architectural Style: 

When selecting an architectural style, please select the option that is the same or a similar design to the principal residence on the property. Common styles in Redlands neighborhoods include Craftsman, Ranch, Spanish, and Mid-Century Modern (although there are also other unique styles). The ADU building materials and colors should be the same or similar to the principal residence (e.g., wood siding, stucco, plaster, etc.).   

Type of Approval:

Ministerial approval of ADUs within a residential or mixed-use zone (i.e., building permit only).
Contact the One Stop Permit Center for application filing requirements and application fee information. 

Owner-Occupancy:

ADUs (attached and detached): The updates to State ADU law removed the owner-occupancy allowance for newly created ADUs effective January 1, 2020. 

Junior ADUs: There are owner-occupancy requirements for Junior ADUs. The owner must reside in either the remaining portion of the primary residence, or in the newly created Junior ADU.

Term of Rental:

ADUs (attached and detached): Must be rented for more than 30 days.

Junior ADUs: No minimum on rental terms (may be rented for less than 30 days).

Home Owner’s Association:

Can a local Homeowners Association (HOA) prohibit the construction of an ADU or Junior ADU?

No. Assembly Bill 670 (2019) and AB 3182 (2020) amended Section 4751, 4740, and 4741 of the Civil Code to preclude common interest developments from prohibiting or unreasonably restricting the construction or use, including the renting or leasing of, an ADU on a lot zoned for single-family residential use. Covenants, conditions, and restrictions (CC&Rs) that either effectively prohibit or unreasonably restrict the construction or use of an ADU or Junior ADU on such lots are void and unenforceable or may be liable for actual damages and payment of a civil penalty. Applicants who encounter issues with creating ADUs or Junior ADUs within CC&Rs are encouraged to reach out to the California Department of Housing & Community Development for additional guidance.

Steps to building an ADU

1. Planning 

• Homework and gather information (available on this webpage)
• Prepare a preliminary Site Plan to verify feasibility (click on Make A Site Plan tab above)
• Early consultation with city staff (Planning, Building, and Engineering staff at the One Stop Permit Center)
• Assemble your project team
• Architect or qualified consultant prepares initial design
• Review initial design with city staff
• Plan refinement

2. Design

• Construction plans prepared by architect or qualified consultant
• Comply with applicable provisions of California Building Code
• Comply with applicable provisions of California ADU law (see Accessory Dwelling Unit Handbook)

3. Permitting

• Application for a building permit
• Plan review by city staff
• Corrections or comments on plans
• Re-submit plans for further review, if required
• Pay any applicable fees
• Permit approval and issuance

4. Construction

• You or your contractor begins work
• Obtain necessary inspections as construction progresses
• Obtain final inspections and sign-off

5. Move-in

Make a Site Plan

You can make a preliminary Site Plan yourself by using the City’s mapping tools available online. A preliminary Site Plan can help you explore the feasibility of building an ADU. A few clicks listed below will help you create and print a Site Plan in just a couple of minutes:

1) Go to the City’s online Zoning Map (click here). 

2) On the top right, click on the “Basemap” button to change the Basemap. You are able to change to Imagery or a darker mode. In case you want to turn off the Zoning layer, click the “Layers” button at the top right section.

3) Find your location on the map, and scroll in for a close-up aerial photo of your property (use the scroll wheel on your mouse, or use the “+” symbol at the upper left side on the map to zoom). For best results, make sure your property occupies most of the map window.

4) On the top toolbar, click on “Print Zoning”. Select the template size (A3 landscape, A3 Portrait, etc.). The Advanced options allow you to select the map print extent (current map extent, current map scale or set map scale).  You can also change the print quality and other map options (legend, north arrow, scalebar units).

5) The Map will show in the Results tab. Click on the map link to open it. You can download it or print it.

6) If you download your map, you can edit it by using any drawing tool (if you have PDF, Photoshop, or similar software) prior to printing. You can also print the page and draw on it. This will become your preliminary Site Plan. Save it to your device or print it.

Measurement Tool: There is a measurement tool available on the Zoning Map that allows you to verify dimensions for the width of walkways, driveways, yards, and setbacks, etc.  At the top right, next to the  Address Locator, click on the “Measure” button and click on the area you want to measure. Then, select the units on the drop-down list.

State law has development standards for yards and setbacks specifically for ADUs (which are not listed in the City’s Zoning Code in RMC Title 18). The standards are different for detached ADUs, attached ADUs, and Junior ADUs. Please refer to the Accessory Dwelling Unit Handbook for further information, and check with a city planner at the One Stop Permit Center should you have any questions. 

How To Measure: Use your mouse and cursor to measure dimensions in feet. The first click of your mouse will start the measurement, and then a double-click will end the measurement. To do another measurement, just just click once again on your mouse and then double-click to end the measurement. You can then draw or write these measurements to provide the required information. 

Property Lines: A quick and easy way to verify your property lines and dimensions is to obtain a free Assessor’s Parcel Map from the County Assessor’s Property Information Management System website (click here). Click on the ‘Parcel Inquiry’ tab and  then enter the property’s Assessor Parcel Number (APN) — you can find the APN on the property tax bill. Then select ‘View ASSR Parcel Map’ tab on the toolbar.

Standard Building Plans

Some cities and counties provide standard building plans (sometimes called “pre-approved” plans) online at no cost. However, applicants may still need to contact the architect or designer of a particular plan set for authorization to use that plan. The links below are provided for informational purposes only.

At this time, the Development Services Department does not offer pre-approved ADU building plans. It is recommended that you hire a California-licensed architect or other qualified design professional to prepare your ADU plans prior to submittal to the City of Redlands Building & Safety Division. All construction plans must be reviewed and approved by staff through the Plan Check process.

A unique Site Plan must still be prepared for the subject property where the ADU is proposed to be located (to include structure setbacks, required yard areas, parking areas and vehicle access, required calculations, etc.). Other site-specific construction plans may also be necessary depending on the project site (e.g., foundation, structural, roof, etc.). The applicant/designer is responsible for ensuring ADU plan submittals meet all applicable design regulations of the California Building Code, California Fire Code, and State ADU law. 

Note: When selecting an architectural style, please select the option that is the same or a similar design to the principal residence on the property (common styles in Redlands include Craftsman, Ranch, Spanish, and Mid-Century Modern, although there are also others). The ADU building materials and colors should be the same or similar to the principal residence.   

Alameda Tiny Homes

City of Concord – ADU plans

San Diego County - ADU Plans

City of Sacramento - ADU Plans

City of Fremont – ADU plans

City of Los Angeles – ADU Plans

Napa Sonoma ADU - ADU Plans

Snap ADU Design Build

City of Del Mar - ADU Plans

City of San Jose - ADU Plans

ADU California.org – Best Practices and links to other useful websites

For more information about how to apply for a building permit, Plan Check submittal requirements, Plan Check application fees, etc., please call the Building & Safety Division public counter at 909-798-7536 in the One Stop Permit Center (click here) between 8:00 AM and 4:30 PM.

How To Apply

Building permits are processed through the Building & Safety Division (referred to as a ‘Plan Check’). Application information is available from Building & Safety staff at the One Stop Permit Center.

Quick links:
Building Permit Application 
Residential Plan Check
CALGreen Residential Checklist

For more information about how to apply for a building permit, Plan Check submittal requirements, Plan Check application fees, etc., please call the Building & Safety Division public counter at 909-798-7536 in the One Stop Permit Center (click here) between 8:00 AM and 4:30 PM.

Impact Fees

New developments often require the payment of Development Impact Fees (DIF) to offset the impacts of such development on public facilities and public services.

However, State law in 2019 updated the requirements for impact fees as they pertain to ADUs (see Assembly Bill 68). Calif. Gov. Code section 65852.2(f) states:
 

• An accessory dwelling unit shall not be considered to be a new residential use for purposes of calculating connection fees or capacity charges for utilities, including water and sewer service, unless the accessory dwelling unit was constructed with a new single-family dwelling.
   
• A local agency shall not impose any impact fee upon the development of an accessory dwelling unit less than 750 square feet.
   
• Any impact fees charged for an accessory dwelling unit of 750 square feet or more shall be charged proportionately in relation to the square footage of the primary dwelling unit.
   
• For an accessory dwelling unit described in subparagraph (A) of paragraph (1) of subdivision (e), a local agency shall not require the applicant to install a new or separate utility connection directly between the accessory dwelling unit and the utility or impose a related connection fee or capacity charge, unless the accessory dwelling unit was constructed with a new single-family dwelling.
   
• For an accessory dwelling unit that is not described in subparagraph (A) of paragraph (1) of subdivision (e), a local agency may require a new or separate utility connection directly between the accessory dwelling unit and the utility. Consistent with Section 66013, the connection may be subject to a connection fee or capacity charge that shall be proportionate to the burden of the proposed accessory dwelling unit, based upon either its square feet or the number of its drainage fixture unit (DFU) values, as defined in the Uniform Plumbing Code adopted and published by the International Association of Plumbing and Mechanical Officials, upon the water or sewer system. 

Click on the following link to view the applicable DIF for Accessory Dwelling Units:
https://www.cityofredlands.org/post/development-impact-fees

Additional Information

The following links and documents are provided for informational purposes only. 

Additional resources and guidance from the California HCD website: 
https://www.hcd.ca.gov/policy-and-research/accessory-dwelling-units

Discover the potential for an ADU on your property: ADU possibilities on your lot (click here)

All About Accessory Dwelling Units by AARP

Office of the State Fire Marshal: ADUs and Automatic Fire Sprinkler Requirements (Information Bulletin 21-005)

Office of the State Fire Marshal – Information Bulletins

Grants & Financing

ADU Grant Program - CalHFA

• The ADU Grant provides up to $40,000 towards pre-development and non-reoccurring closing costs associated with the construction of the ADU.
• Predevelopment costs include site prep, architectural designs, permits, soil tests, impact fees, property survey, and energy reports.
• All funds for the ADU Grant program were fully reserved as of March 1, 2023, for up to $100 million in grants statewide. 
• As of December 28, 2023, all funds have been fully allocated. 
• Click on the following link for further information: https://www.calhfa.ca.gov/adu/
• Brochure: ADU Financing Program
   

Cost of building an ADU

L.A. County ADU Construction Cost Calculator

ADU Investment Return Calculator

ADU Finance Guide for Homeowners