ADU rules in Moscow

A detached backyard ADU is allowed by right in every Moscow zone that permits a single-family dwelling. The Sec. 3-4 Land Use Table marks 'Accessory Dwelling Unit' as PA (permitted accessory use) in the AF, FR, SR, R-1, R-2, R-3 and R-4 zones, exactly the seven zones where the table marks single-family dwellings P. The Sec. 1-6.D.1 definition expressly covers a unit 'added to, created within, or detached from the principal dwelling unit.' There is no minimum lot size: Ordinance 2019-12 (12/2/2019) struck the sentence that had made undersized lots ineligible. Because a detached ADU is also an accessory building, the Sec. 6-1 setback rules apply on top of the ADU standards.

Moscow does not split attached, internal and detached ADUs into different tracks: all three are the same use. The Sec. 1-6.D.1 definition reads 'A secondary dwelling unit that is accessory to a single family dwelling on a single lot, containing complete housekeeping facilities and which is added to, created within, or detached from the principal dwelling unit,' and the single Land Use Table row covers the whole definition as PA in AF, FR, SR, R-1, R-2, R-3 and R-4. A basement conversion, an internal unit or an addition therefore faces the same Sec. 3-5.A standards as a backyard cottage: 600 sq ft or 40 percent, two occupants, the owner-occupancy deed restriction and one parking space.

Sec. 3-5.A.2.b caps ADU floor area at 600 square feet or 40 percent of the gross floor area of the principal dwelling, whichever is less, and Sec. 3-5.A.2.c separately limits the ADU to two residents. Both numbers are below the floors Idaho Code 67-6541(2)(d) sets for covered cities, which bars capping an ADU below 1,000 square feet or 75 percent of the primary dwelling; that subsection binds through mandatory local amendments due by February 1, 2027, so the 600 sq ft cap is the operative local rule today but is scheduled for replacement. A conformance ordinance that would raise the cap to 1,000 square feet or 75 percent and the occupancy cap from two to four cleared its Planning and Zoning Commission public hearing on August 12, 2026 on a unanimous 6 to 0 recommendation of approval, but it is still an unnumbered draft (Ordinance No. 2026-__) and changes nothing until the City Council adopts it. Moscow sets no ADU-specific height limit; the Sec. 6-1 accessory-building rules cap a detached unit's top plate line at 14 feet where it encroaches into the rear yard.

Sec. 3-5.A.2.d requires the owner to record a deed restriction, approved by the City Attorney and binding on heirs, assigns and subsequent purchasers, before a building permit for the ADU will issue, promising that the owner will live on the property in either the principal dwelling or the ADU. Owner occupancy is defined as legal residence at the property, evidenced by voter registration or similar means, for more than six months in any year; a named natural person with an interest in a private trust counts, a corporate trust does not. The Zoning Administrator may waive it for absences over six months for military service, an employment sabbatical or qualified family medical leave, and other temporary waivers go to the City Council. If the owner cannot live on site, only one of the two dwelling units on the property may be occupied. Idaho Code 67-6541(2)(e) forbids an owner-occupancy requirement for either unit and gives covered cities until February 1, 2027 to repeal it; the conformance ordinance that strikes subsection d in full won a unanimous Planning and Zoning Commission recommendation on August 12, 2026 and now awaits City Council adoption, so the recorded deed restriction is still required today.

Two provisions say the same thing. Sec. 3-5.A.2.e requires one off-street parking space for the ADU in addition to that required for the principal dwelling, and the Sec. 6-2.E.7 minimum parking table lists 'Accessory Dwelling Unit / 1 in addition to principal structure requirements' under Accessory Uses. The principal single-family dwelling itself needs 2 spaces plus 1 per bedroom over four, so a typical lot needs three. Idaho Code 67-6541(2)(b) will forbid requiring any ADU off-street or guest parking unless the principal dwelling has no off-street parking, the street is unpaved or not designed for on-street parking, or the principal dwelling is within a quarter mile of transit, an employment area or commercial services; covered cities have until February 1, 2027 to conform. Moscow's conformance ordinance, recommended for approval by the Planning and Zoning Commission on August 12, 2026 and still awaiting City Council adoption, would keep the one-space requirement only where the property currently provides no off-street parking for the principal dwelling.

The Land Use Table marks ADUs 'PA', which Sec. 3-2.B defines as a use 'allowed only as accessory or incidental to a permitted principal use', not 'C', the marker Sec. 3-2.C reserves for uses needing a Conditional Use Permit under Sec. 8-4. Review is administrative: Sec. 11-2 requires a Zoning Certificate from the Zoning Administrator before a structure may be occupied or its use changed, and Sec. 3-5.A.2.d assumes a building permit. There is no public hearing and no Board of Adjustment step for a conforming ADU. Idaho Code 67-6541(3), in force since July 1, 2026, independently requires that conforming ADU projects 'be approved administratively and as a matter of right, without the need for discretionary approval.' Note that a detached accessory building of 1,001 to 1,500 sq ft is a Conditional Use in the residential zones, but the 600 sq ft ADU cap keeps that off the table today.

Moscow's zoning code contains no prohibition on renting an ADU; the practical limits are the owner-occupancy deed restriction of Sec. 3-5.A.2.d, which forces the owner to live in either the house or the ADU, and the two-person occupancy cap of Sec. 3-5.A.2.c. Nothing in the code allows an ADU to be sold separately from the principal dwelling, which the Sec. 1-6.D.1 definition ties to a single lot. Short-term lodging of less than 21 consecutive days per guest is Moscow's 'Bed and Breakfast Inn' use, and Ordinance 2026-04 (adopted 7/6/2026) made Bed and Breakfast Inns a permitted use in every zone that allows single-family dwellings, its recitals citing House Bill 583's amendment of Idaho Code 67-6539 as the reason. Under that rewritten statute, effective July 1, 2026, no city may require a license, fee, permit, certification or registration to operate a short-term rental, or impose owner occupancy, extra parking, day limits, inspections or a conditional use permit in a residential zone. Moscow imposes no separate short-term rental license, but two pieces of residual local text conflict with the statute: the Sec. 1-6.D.16 definition of a Bed and Breakfast Inn still requires that 'the owner resides upon the property', and the Sec. 6-2.E.7 table still assigns 0.5 parking space per bedroom to a Bed and Breakfast.