Accessory Structures in Idaho (2026)
27 rules on the books across Idaho, 8 cities and counties. Select a rule to read the full details.
Severity: Few Restrictions · Light Restrictions · Some Restrictions · Significant Restrictions · Heavy Restrictions
ADU Rules
Rules for building accessory dwelling units (granny flats, in-law suites) including size limits, parking requirements, and owner-occupancy rules.
Ada County
Some RestrictionsUnincorporated Ada County allows one secondary (accessory) dwelling per lot of at least 6,000 square feet. It must be…
Read full rule →Boise
Some RestrictionsBoise allows up to two accessory dwelling units per single-family lot, capped at 900 square feet or 70% of the primary…
Read full rule →Caldwell
Some RestrictionsCaldwell allows accessory dwelling units as an accessory use under Section 10-12-03-1, requiring compliance with the…
Read full rule →Kootenai County
Some RestrictionsUnincorporated Kootenai County allows one accessory living unit per parcel with an accessory living unit permit from…
Read full rule →Meridian
Some RestrictionsMeridian caps accessory dwelling units at 900 square feet or half the primary home, requires a city permit, and limits…
Read full rule →Nampa
Some RestrictionsNampa allows one detached accessory dwelling per single-family lot, capped at 500 square feet with only one bedroom, no…
Read full rule →ADU Impact Fees
Impact fees, school fees, utility hookup charges, and waivers for ADUs. Many jurisdictions exempt ADUs under 750 sq ft from impact fees per state law.
ADU Owner Occupancy
Whether the property owner must live on-site to operate an ADU, deed-restriction requirements, and recent state-law changes lifting owner-occupancy rules.
Ada County
Significant RestrictionsAda County Code 8-4-23(B)(3) requires that either the principal home or the secondary dwelling stay continuously…
Read full rule →Boise
Significant RestrictionsInside the Harris Ranch Specific Plan area, Boise requires the principal home or its accessory dwelling to stay…
Read full rule →Canyon County
Some RestrictionsCanyon County Code § 07-14-25 requires the owner of the lot to live on site wherever a secondary residence, the…
Read full rule →ADU Rental Restrictions
Whether an ADU can be rented short-term (Airbnb), 30-day minimums, separate rental licenses, and long-term lease requirements.
Shed & Carport Rules
When a storage shed or carport needs a permit, the square-footage exemption thresholds, and the setback and height limits that apply either way.
Ada County
Some RestrictionsIn unincorporated Ada County, a detached accessory structure (shed, garage, workshop) may not exceed 24 feet in height…
Read full rule →Boise
Some RestrictionsDetached carports in Boise can't sit in front of the house or encroach into front and street-side setbacks without a…
Read full rule →Bonneville County
Some RestrictionsIn Bonneville County's unincorporated residential zones, a shed or other accessory building cannot cover more than 30%…
Read full rule →Caldwell
Some RestrictionsCaldwell tiers accessory building setbacks by size: structures under 200 square feet need only a 3-foot setback, while…
Read full rule →Canyon County
Some RestrictionsUnincorporated Canyon County, Idaho treats a shed as an 'accessory structure,' defined in Canyon County Code § 07-02-03…
Read full rule →Kootenai County
Some RestrictionsIn unincorporated Kootenai County, a one-story detached storage shed 200 sq ft or smaller needs no building permit, but…
Read full rule →Meridian
Some RestrictionsMeridian exempts one-story detached tool and storage sheds, playhouses, and similar accessory structures from a…
Read full rule →Nampa
Some RestrictionsIn Nampa's RS residential zone, sheds over 200 square feet need a building permit and full setbacks; smaller sheds skip…
Read full rule →Garage Conversions
Rules for converting a garage into living space, including whether you need to replace the lost parking and what building codes apply.
Ada County
Some RestrictionsUnincorporated Ada County lets you convert an existing garage, basement, or detached accessory structure into a…
Read full rule →Boise
Some RestrictionsBoise allows turning a garage into living space as an accessory dwelling unit, but only if replacement off-street…
Read full rule →Tiny Homes
Zoning rules for tiny houses on wheels and foundations, including minimum square footage requirements and where they can be placed.
Ada County
Some RestrictionsAda County's zoning code treats a tiny home as a manufactured home. A tiny home used as a second unit must meet the…
Read full rule →Boise
Some RestrictionsBoise allows a tiny home on wheels as an accessory unit to a single-family home, capped at 400 square feet and subject…
Read full rule →Bonneville County
Some RestrictionsBonneville County's floodplain code classifies tiny homes as manufactured homes and recreational vehicles. Any tiny…
Read full rule →Canyon County
Some RestrictionsUnincorporated Canyon County builds tiny homes under Appendix R of the 2018 International Residential Code, adopted at…
Read full rule →Kootenai County
Some RestrictionsKootenai County has no dedicated tiny-home ordinance. A tiny home on wheels is a recreational vehicle or park model RV…
Read full rule →Caldwell
Light RestrictionsCaldwell's zoning definitions treat a detached tiny home built to the International Residential Code as a form of…
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