Most localities would allow separate homes on single-family lots

Local zoning rules would allow accessory dwelling units in single-family areas, and localities would have to allow at least one where they allow single-family homes. An ADU is an attached or separate home on the same lot as a proposed or existing main home, with facilities for living, sleeping, eating, cooking, and sanitation. Applicants would need a local permit. The permit fee could be no more than $500, plus other applicable fees. The section would not apply to a locality that adopted an ADU ordinance before January 1, 2026, if that ordinance does not treat an attached or detached ADU as a special use. The proposed rules would take effect July 1, 2027. They would not cover ADU permits approved before that date.

Localities could set certain limits on ADUs, including rental, parking replacement, size, safety, and owner-occupancy rules. These options would apply to localities covered by the proposed section. A locality could require rentals to last at least 30 days, replacement of required parking removed by construction, and compliance with building, utility, emergency access, flood, stormwater, and historic-area rules. A locality could require the owner to live in either the ADU or main home only when the owner applies to build or convert the ADU. It could also bar ADUs on lots with more than one home and prevent separate sales or subdivision.

Localities could not require new parking in most cases, large setbacks, certain stricter zoning limits, street improvements, or family ties between ADU residents and the main home's residents. These limits would apply to local governments covered by the proposed section. A locality could require new parking only where on-street parking is always prohibited. It could require repair or rebuilding of a public street disturbed by ADU construction. The proposal would not override private real estate agreements or community rules.