Sweeping residential zoning reform becomes law in Idaho

Idaho Gov. Brad Little signed into law a sweeping set of housing reforms as lawmakers sought to avoid a piecemeal legislative approach to the state’s housing affordability problem.

The legislation gave local governments more power to implement plans on missing middle housing, but took control away in some zoning.

Like Sun Belt states, Mountain West states such as Idaho saw population booms during the COVID-19 pandemic that overwhelmed housing supply. Remote workers left high-cost states such as California and New York for lower-cost areas, pushing prices higher in the places they landed.

Return‑to‑office policies have pulled workers back to their previous states, driving housing prices lower in cities where new construction surged. Austin, Texas, once a hotspot for price growth, now leads the nation in rent declines and ranks among the top cities for falling home prices as tech talent returns to the coasts.

Hollie Conde, a fellow at think tank Sightline Institute, told The Builder’s Daily that the scenario hasn’t happened in Idaho.

“So far, they have kept their jobs,” Conde said. “It’s come so far that we have people in the legislature that have lived here for five, six years.”

Solving a housing affordability problem

The new population brought big salaries and buying power that drove housing prices beyond what the average Idaho resident could afford.

Mountain West cities led the 2025 Urban Land Institute’s Terwilliger Center Home Attainability Index with percentage increases in home prices, citing data from 2019 to 2023. Boise’s metropolitan area topped the list, Coeur d’Alene, Idaho Falls and Twin Falls in the Top 10.

Last year, state lawmakers created a committee to study state and local land-use regulations and their impact on housing supply. The committee returned with recommendations, many of which are now law.

As is typical in other states, local governments fought the changes and still aren’t happy with the results. Coeur d’Alene city officials called the bills “dumb” and “not very clever” during a public meeting Tuesday, a local newspaper reported.

Manufactured housing — H800

Idaho law now treats manufactured homes, including manufactured duplexes and other multi-dwelling units, similarly to site-built single-family and multifamily housing for siting purposes. It lowers minimum size requirements and clarifies that single-section and smaller units cannot be zoned out.

Cities must allow manufactured single-unit homes wherever they permit single-family housing, while manufactured duplexes are limited to multifamily zones.

Lot splits for ADUs — H707

Subdivision law now includes an administrative path for cities and counties to approve limited lot splits. The property must already have an existing or approved ADU or secondary unit, mainly to enable separate ownership or financing.

The split does not add new dwelling entitlements or density beyond what zoning already allows and is “one and done” for the parent parcel. Each resulting lot must still meet local infrastructure, setback and building requirements.

Single-stair — H706

Changes to the Idaho Building Code Act let local governments approve small apartment buildings with a single interior exit stairway. Those buildings must meet strict life-safety standards and are limited in height, unit count and floor area. They also must have full sprinklers, pressurized two-hour-rated stairs, fire-rated corridors, short exit travel distances and robust smoke and fire detection.

ADUs — S1354

The zoning reform requires cities to allow accessory dwelling (ADUs) units by right as a residential use in many places. It prevents local governments and homeowners’ associations from flatly banning ADUs. The law guarantees at least one ADU per lot in covered jurisdictions.

It also bars local rules that impose hard maximum size caps, but still allows health, safety and infrastructure standards.

Starter homes / small lots — S1352

State law now preempts certain local regulations to protect “starter home subdivisions” on at least four acres. It prevents cities from banning these projects through large minimum lot sizes and other dimensional standards.

The law bars local rules that require lots above a defined minimum size, such as 1,400 square feet, or impose certain setbacks, depths and fees. It also pushes cities to permit smaller lots and higher minimum densities, around 12 units per acre, subject to infrastructure limits, for these starter home projects.