At-a-Glance Law Summary

Allowance

ADUs must be allowed by administrative approval in subject jurisdictions:

• Municipalities within MPOs with a population 1,000 and over
• Census Designated Places within MPOs over 40,000 population

Approval or denial must be based on compliance with Objective Standards included in the land use code or other ADU regulations. Applies to all lots that allow the construction of Single-Unit Detached Dwelling, regardless of zone (including Planned Unit Developments) or HOA rules.

Optional: Other jurisdictions can opt-in to access grants and financing.  Subject jurisdictions may exempt some parcels, such as those in floodplains and that lack access to a domestic water and sewer system.

ADU Definition

Cannot define ADUs in such a way that excludes internal, attached, or detached ADUs.

The law defines an Accessory Dwelling Unit as “an internal, attached, or detached dwelling unit that: (a) provides complete independent living facilities for one or more individuals; (b) is located on the same lot as a proposed or existing primary residence; and (c) includes facilities for living, sleeping, eating, cooking, and sanitation.”

Optional: Can define ADUs to include or exclude types of housing, like motor homes, recreational vehicles, or multi-purpose trailers.

Square Footage

Must allow ADUs 500 to 750 square feet regardless of the primary structure’s size.

Optional: The size range can be expanded to include units smaller than 500 square feet and larger than 750 square feet. It can also permit ADUs to exceed the size of the primary residence or, alternatively, cap their size so they do not surpass that of the main home.

Why? Size restrictions based on the primary dwelling or minimum lot sizes can prevent lower income homeowners with smaller homes from building an ADU. Studies have also shown that 800 square feet ADUs can help fill the 2-bedroom unit gap that many jurisdictions are currently experiencing.

Setbacks

Cannot apply larger side or rear setbacks than what is in the law:

• Side Setbacks: Cannot be larger than setbacks for a single-unit detached unit in the same zone.
• Rear Setbacks: Cannot be larger than what applies to accessory building types (like sheds) or five feet, whichever is greater.

Optional: Allow ADUs in front setbacks or apply smaller side or rear setbacks.

Why? Setbacks should not prevent an ADU from getting built on most lots, particularly in walkable, transit-served, desirable neighborhoods where more housing units, particularly more affordable options, are needed.

Minimum Lot Size

Cannot be more restrictive than a single-unit detached unit in the same zone.

Design

Cannot require architectural style, building materials, and/or landscaping that is more restrictive than the primary home.

Factory-Built ADUs

Cannot apply more restrictive design or dimensional standards.

Parking Requirements

Cannot automatically require new off-street parking for ADUs.

Can require one off-street parking space, if:

• an existing driveway, garage, tandem parking space, or other off-street parking space is already existing and available, or
• a driveway, garage, tandem parking space, or other off-street parking space does not exist; property is located in a zoning district that as of January 1, 2024 requires one or more parking spaces for the primary home; and property is located on a block where on-street parking is prohibited.

Why? Cost can be prohibitive ($4,000-$10,000). Parking impacts are likely to be minimal given the rate of ADU construction, and lack of space for parking can prevent some ADUs, particularly for lower income homeowners who often have smaller lots.

Historic Districts

Can still apply to ADUs.

Owner Occupancy

Cannot require the owner to live in the primary dwelling long term.

Optional: Can require the owner to live in primary dwelling at the time of permitting an ADU (except for if the primary unit is being built at the same time), or if applying for an STR license or permit.

Why? Owner occupancy restrictions limit flexibility, can be difficult to enforce, and can deter homeowners from building. Also, requiring owner occupancy can limit financing options; if the owner has to foreclose they will be in violation of the covenant, which unfairly impacts those who can’t pay for an ADU outright.

HOAs

HOAs cannot restrict ADUs based on design and dimensional standards. “Reasonable restrictions” are still allowed, that do not unreasonably increase the cost or prohibit the construction of an ADU.

Multiple ADUs

Optional: Can allow more than one ADU per lot. The law does not define multifamily housing, so local jurisdictions may use their own definitions.

Short-Term Rentals

Optional: Can regulate.

Impact Fees

Optional: Can apply impact or other similar fees.