The package
Governor Brad Little signed a group of housing bills across two dates in the closing days of the 2026 session: Senate Bill 1354 on March 31 and House Bill 706 on April 2. Together they constitute one of the broader state preemptions of local residential zoning enacted this year, and all take effect July 1, 2026.
House Bill 800 requires factory-built manufactured homes to be treated the same as traditional site-built single-family or multifamily housing. Senate Bill 1354, signed as Session Law Chapter 265, removes homeowners-association and local bans on internal accessory dwelling units, allowing at most one internal ADU per homestead by right where health, safety and infrastructure standards are met; it passed the Senate 25-10 and the House 47-23 before enrollment.
Senate Bill 1352 sets a statewide minimum lot size of 1,500 square feet for starter-home subdivisions, reduces setbacks and eliminates certain dimensional requirements. It passed the Senate by the same 25-10 margin as SB 1354, with an overlapping but not identical set of dissenters.
The single-stair bill is the technical one
House Bill 706 amends the Idaho Building Code Act, adding section 39-4109C to permit residential buildings of up to six storeys served by a single interior exit stairway. It cleared the House 63-7 on March 24 and the Senate 18-17 on April 1 before Governor Little signed it the next day, with an emergency clause making it effective July 1, 2026 rather than the standard July 1 following adjournment.
The trade-offs are written into the statute: buildings using the exception are capped at four dwelling units per floor and 6,000 square feet of gross floor area per story, must be of Type I through V construction, and must carry a full NFPA 13 automatic sprinkler system throughout. The single stairway must have self-closing, alarm-interconnected doors, a two-hour fire-resistance rating on the stair and elevator shaft enclosures, minimum stairway widths, fire-rated corridors separating unit doors from the stairway, limited travel distances to exits, and emergency escape and rescue openings in habitable rooms.
Analysis: the second staircase requirement is a major constraint on small-lot apartment design, because two stairs and the corridor connecting them consume a large share of the floor plate on a narrow parcel. Removing it while adding active fire-protection requirements is the trade European and Canadian codes have long made. Idaho joins a short list of US states to codify it.
Paired with the 1,500-square-foot lot minimum, the practical effect is to make small infill sites buildable that were previously uneconomic under local dimensional rules.
Scale of the problem, and limits
Senator Ben Toews, floor sponsor of both SB 1354 and SB 1352, has estimated Idaho's housing shortage at approximately 44,500 homes. That is a legislator's own estimate rather than an audited figure and should be read as such.
The laws set what is permitted; they do not by themselves produce housing, and local jurisdictions retain discretion over health, safety and infrastructure standards, which is where implementation disputes usually arise. Because HB 706 authorizes rather than mandates the single-stair exception, cities that decline to adopt a qualifying local ordinance will see no change to their building code minimums.