Accessory Dwelling Units

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, attached, or existing space conversion;
• One (1) Junior ADU within an existing or proposed single-family dwelling; and,
• ADU per Gov. Code Section 66323. 
• 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 (Gov. Code Section 66323 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: Maximum 1,200 square-feet of interior living space.

Attached ADU: Maximum of 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: Maximum 500 square-feet of interior living space.

• 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 (note: exceptions may apply to Gov. Code Section 66323 units – refer to HCD Handbook). 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): Only ADUs which are sold separately to a qualified buyer under Government Code section 66341, subdivision (c)(3), can require owner-occupancy. Otherwise, a local agency cannot impose an owner-occupancy requirement on any other ADU (Gov. Code, § 66315).

Junior ADUs: Yes, under certain circumstances. If a JADU has shared sanitation facilities with the primary structure, owner-occupancy will be required. If the JADU does not have shared sanitation facilities, or the owner is another governmental agency, land trust, or housing organization, owner-occupancy will not be required. The owner must reside in either the remaining portion of the primary residence or in the newly created JADU. (Gov. Code, § 66333, subd. (b).) Additionally, JADUs cannot be used as short-term rentals and, if rented, must be rented for longer than 30 days (Gov. Code, § 66333, subd. (g).)

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).

Senate Bill (SB) 9 and ADUs:

SB 9 (Gov. Code, §§ 65852.21 and 66411.7) and ADU Law are complementary. Both laws can be used together to create varying combinations of “SB 9 units” and ADUs. SB 9 allows for a lot to be split, with each of the two resulting lots eligible for up to two primary units. These primary units are distinct from ADUs and JADUs created under ADU Law and must be approved ministerially.

When a lot split occurs, SB 9 requires the local agency to approve up to two units on each parcel but specifically states that only two units are allowed per parcel, despite what ADU Law would otherwise allow. Those two units could be two primary “SB 9 units,” or one primary unit and one ADU, or one primary unit and one JADU. But in no case is a local agency required to permit more than two units on either of the two parcels resulting from an SB 9 lot split.

When an SB 9 lot split has not occurred, the lot is eligible to receive up to two primary units under SB 9, as well as whatever combination of ADUs and JADUs it would otherwise be entitled to under ADU Law if SB 9 was not being used. In some instances, this may result in a total number of units on the parcel that is greater than what either SB 9 or ADU Law would allow on its own. However, if ADU Law is used on its own or in combination with SB 9 to create more than four total units on the lot, a local agency is not required to approve a lot split under SB 9.

See HCD’s SB 9 Factsheet for more information and resources.