Tiny home on wheelsThis is a significant update from an earlier, more generic draft. Boise updated its zoning code effective July 1, 2025 to allow certified tiny homes on wheels (ANSI A119.5 or NOAH-certified) as ADUs — property owners can now place up to two THOWs on a single-family lot, or one THOW plus one conventional ADU. Blaine County (Sun Valley area) has one of the most explicit THOW-friendly frameworks in the country, tied to lot acreage: THOWs are generally prohibited under 1 acre, allowed with a conditional use permit on 1–2 acres, and allowed by right on lots over 2 acres.
ADU / accessory unitIdaho now has a real, very recent statewide ADU mandate. Senate Bill 1354, signed by Gov. Little on March 31, 2026 and effective July 1, 2026 (codified at Idaho Code §67-6541), prohibits any city over 10,000 population from banning detached ADUs outright and eliminates owner-occupancy requirements statewide. Cities have until February 1, 2027 to raise their minimum ADU size protection to at least 1,000 sq ft or 75% of the primary home. An earlier, more modest law (HB 166, 2023) had only barred HOAs from blocking internal ADUs. Rural counties outside qualifying cities are not covered by SB 1354's mandate.
Minimum square footageSB 1354 requires cities over 10,000 population to protect at least 1,000 sq ft (or 75% of primary home) by Feb. 1, 2027; smaller cities and counties vary
Foundation requirementFoundation-built ADUs have the strongest and most recent statewide backing of any state covered here outside the original ADU-preemption states (CA/OR/WA/CO)