Idaho Tiny Home Zoning Laws
Idaho was one of the first states in the country to adopt IRC Appendix Q for tiny homes, and that early move has translated into genuinely active local policy since — including a real, current example driven by one of the most expensive housing markets in the United States.
- One of the first states nationally to adopt IRC Appendix Q for tiny homes.
- HB 166 (2023) only restricts HOA covenants on internal ADUs — it does NOT stop cities/counties from banning detached ADUs (a common misconception).
- The real "cities can't ban ADUs" law is SB 1354 (2026), a much newer, stronger statute.
- Blaine County (Sun Valley area), facing a severe housing shortage, actively updated rules to allow tiny homes as ADUs.
- Confirm which law you're reading about — many sources conflate HB166 and SB1354 incorrectly.
A real, current story worth knowing: Blaine County, home to the Sun Valley resort area, is consistently ranked among the most expensive housing markets in the country, creating a severe shortage of workforce housing.7 In response, Blaine County and the cities of Hailey, Bellevue, and Sun Valley have updated their regulations specifically to allow tiny homes as ADUs on qualifying properties.7 As of March 2026, Snake River Tiny Homes was hosting a public "Tiny Homes 101" workshop in Hailey specifically covering how to legally place tiny homes as ADUs for family, workforce, or rental use — a live example of this policy shift translating into real community engagement.7
1. Two Different State Laws, Often Confused
House Bill 166 (2023) is frequently described online as barring cities and counties from banning ADUs outright — but that's not what it actually does. The original bill would have done that, but the provision was stripped out in the Senate before passage. As enacted, HB 166 only prevents HOAs from enforcing covenants that ban "internal ADUs" (units inside the primary home or its attached or detached garage) on owner-occupied properties; it left cities and counties fully free to ban detached ADUs through zoning, and required owner-occupancy for the internal ADUs it does protect.4,9
The law that actually restricts city and county ADU bans is much newer: Senate Bill 1354, signed by Governor Brad Little on March 31, 2026 and effective July 1, 2026, codified at Idaho Code § 67-6541. It bars cities from banning ADUs and eliminates city-level owner-occupancy requirements, closing the gap HB 166 left open.9 If you're researching Idaho ADU rights, make sure whatever you're reading distinguishes between these two laws, since a lot of existing content online (including a prior version of this page) attributes SB 1354's stronger protections to HB 166.
2. County Examples
| County / City | Notable Rule |
|---|---|
| Jefferson County | Requires a minimum of one acre for private tiny home placement; R1 zones allow one home per acre, R5 zones only one home per five acres6 |
| Gem County | One of Idaho's most tiny-home-friendly counties, allowing THOWs with standard zoning compliance3,5 |
| Ada County (Boise) | Actively working to integrate tiny homes into urban areas; permits modular homes on permanent foundations under the One-and-Two-Family Dwelling Code5 |
| Blaine County | Allows both ADUs and THOWs classified as ADUs, driven by acute workforce housing needs4,7 |
| Moscow | Allows THOWs specifically in mobile home parks with full-time utility hookups5 |
| Idaho Falls | Prohibits RVs from being used as ADUs, unlike Blaine County4 |
3. ADU Size Ranges
ADU size limits in Idaho typically range from 500 to 1,200 square feet, though this varies significantly by county and city.4 Park model tiny homes built to ANSI 119.5 and RVIA-certified are classified as recreational vehicles, and RVIA certification specifically broadens where they can be used, since it affirms fire, power, and plumbing safety standards that some jurisdictions require before allowing RV-classified structures as ADUs at all.3,4
4. Homes on Wheels Outside of ADU Arrangements
Generally, THOWs cannot be set up as a standalone residence in a standard residential zone and are typically restricted to RV parks, though individual counties and cities vary in how strictly this is enforced.6 Private landowners generally need at least one acre for zoning compliance regardless of structure type.8
Research record: The HB 166 correction above is the most significant fix in this update. We verified it by reading BoiseDev's contemporaneous 2023 reporting on the Senate's amendment process, Idaho Freedom Foundation's clause-by-clause bill analysis, and the actual enrolled bill text on the Idaho Legislature's site, then cross-checked SB 1354's 2026 signing against Steel Structures America's before-and-after comparison. Many existing sources online, including ones we'd previously relied on, repeat the "HB 166 bans city ADU bans" claim without checking the Senate amendments; we did not want to repeat that error here. Information last checked August 2026.
How to Verify Your Specific Situation
- Confirm your target county's minimum lot size requirement for tiny home placement, since this varies from roughly one acre in Jefferson County to more flexible rural minimums elsewhere.
- If pursuing the ADU route, confirm whether your jurisdiction allows RV-classified structures as ADUs (like Blaine County) or prohibits them (like Idaho Falls).
- If in a high-cost resort area like Blaine County, check for active workforce-housing-driven policy changes, since these areas are moving faster than many rural counties.
- Confirm RVIA certification status for any park model home before assuming ADU eligibility.
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- The Land Geek, "Off Grid Laws In Idaho: Buyer's Guide (2026)."
- World Population Review, "Tiny House Laws by State 2026."
- Great Lakes Tiny Home, "What Counties in Idaho Allow Tiny Houses."
- Zook Cabins, "ADU Regulations In Idaho (2026 Guide)."
- Elite Nest, "What Counties in Idaho Allow Tiny Houses."
- TinyHouse.com, "Idaho's Tiny Home Rules and Regulations."
- Snake River Tiny Homes, "Tiny Homes 101 Workshop in Hailey, Idaho," March 2026.
- Tinyhousel, "Tiny House Zoning Laws by State: Complete Guide."
- BoiseDev, "Senate cuts out major provisions of bill overriding ADU bans statewide," March 2023; Idaho Freedom Foundation, HB 166 bill analysis; Steel Structures America, "Idaho ADU Law Changes," June 2026; primary source: Senate Bill 1354 (2026), official bill page via the Idaho State Legislature.
