States are making ADUs easier to build. Now it’s up to municipalities to follow suit.

States across the nation are enacting legislation to streamline accessory dwelling unit construction as a solution to housing shortages, with California leading the charge by passing five new ADU-related laws in 2024.

Colorado, Arizona, Massachusetts, and Hawaii also enacted significant ADU legislation this year, following standard approaches that make ADUs legal by right, eliminate parking requirements, prevent municipalities from imposing stricter design standards than primary dwellings, and ease owner-occupancy requirements.

Massachusetts officials project their new law allowing ADUs under 900 square feet by right will generate 8,000 to 10,000 units over five years.

For California property owners and developers, these developments signal continued momentum behind ADU liberalization, building on the state's ADU framework that dates back to 1982.

However, the effectiveness of state-level reforms ultimately depends on local implementation, as municipalities remain the primary gatekeepers for ADU approval processes.

Impact fees charged by local utilities and governments are emerging as a critical barrier, with costs potentially high enough to discourage ADU development despite simplified regulations.

As thirteen states have now passed ADU reform legislation, California homeowners may find expanded opportunities to add rental units or housing for family members, though success will vary significantly based on how individual cities and counties choose to implement these state mandates.