Compare ADU rules across Wyoming

Casper allows accessory dwelling units in exactly one zoning district, R-2 (One Unit Residential), and only with a conditional use permit: CMC 17.32.030 lists "Accessory dwelling unit" at subsection J among the R-2 conditional uses. No ADU appears anywhere in the permitted or conditional use lists for R-1 Residential Estate (17.28.020 and 17.28.030), AG Urban Agriculture (17.24.020 and 17.24.030), R-3 (17.36.020 and 17.36.030), R-4 (17.40.020 and 17.40.030) or R-5 (17.44.020 and 17.44.030). A detached unit in R-2 needs the permit on a second, independent ground as well: CMC 17.12.250(D) bars more than one principal building on a lot in R-1 and R-2 unless a conditional use is approved, while permitting multiple principal buildings outright in every other district. The provisions are old and stable; they predate the code's online disposition tables and no ordinance through Ord. No. 03-26 of April 21, 2026 has touched them.

Ordinance read August 2026

The same single listing covers attached and internal units, because CMC 17.08.010 defines an accessory dwelling unit as a habitable living unit "added to, created within, or detached from a single-family dwelling unit." A basement conversion, an internal unit or a rear addition in R-2 is therefore the identical conditional use as a backyard cottage and needs the same Planning and Zoning Commission hearing; Casper's code offers no lighter administrative track for interior conversions. Outside R-2 there is no ADU pathway at all, but in R-3, R-4 and R-5 a second attached unit is simply a permitted two-family dwelling (17.36.020(B), 17.40.020(C), 17.44.020(B)) needing only a building permit, which in practice makes those zones an easier place to add a unit than R-2.

Ordinance read August 2026

Every accessory dwelling unit in Casper needs a conditional use permit from the seven-member Planning and Zoning Commission after a noticed public hearing. For a site under three acres, written notice goes to every private property owner within a three hundred foot radius thirty days ahead of the hearing, with published notice at least fifteen calendar days out (CMC 17.12.240(D)). Since Ord. No. 18-25 took effect on January 20, 2026, an affirmative decision requires "the concurring vote of a majority of all members" of the commission, four of seven regardless of how many attend (17.12.210(B) and 17.12.190(A)), so absences now function as no votes. The commission must find the use consistent with the title's spirit, purpose and intent and compatible with adjacent land uses (17.12.240(G)), may impose continuing conditions, and the permit is void if the work is not completed within one year of issuance (17.12.240(I)). An aggrieved party may appeal to the city council within ten calendar days (17.12.240(L)). The city's current Conditional Use Permit application carries a $600 non-refundable fee and applications are due about thirty days before the commission's monthly meeting, the second Thursday. Once the conditions have been performed the use "shall be considered to be a permitted use" (17.12.240(J)).

Ordinance read August 2026

Detached ADUs are allowed, but the path depends on the zoning district and the lot. The Residential Land Use Table marks 'Accessory dwelling unit' as an 'A' (permitted accessory use by right) in RR, R-2, R-2MH, R-3, R-4 and the Mobile Home Park district, and as a 'C' (conditional use, decided after a noticed public hearing) in R-1 Single Family Residential. Section 10-8-2(A)(1) allows the unit above or within a residential garage or other accessory building, or within a separate accessory building on the same parcel as a detached single-family dwelling. Two hard gates apply everywhere: the lot must be at least 7,000 square feet, and the ADU must be accessory to a detached single-family dwelling, so a lot already holding two or more dwellings cannot add one.

Ordinance read August 2026

Attached and internal ADUs run on exactly the same permission track as detached ones: one land use row, one set of supplemental standards. Section 10-8-2(A)(1) lists placement 'Within a detached single-family dwelling, either initially at time of construction, or any time thereafter' and 'Within an addition to a detached single-family dwelling', and the zoning definition in 10-2-1 describes an ADU as 'An independent, self-contained dwelling unit within or attached to a detached single-family dwelling or building accessory thereto.' That means by right in RR, R-2, R-2MH, R-3, R-4 and MH Park, conditional use permit in R-1, and the same 7,000 square foot minimum lot. A basement conversion gets one break the detached form does not: where the ADU occupies one level of an existing building and the rest of that level cannot practically stay with the primary dwelling, the reviewing official may let the ADU take the whole level.

Ordinance read August 2026

Owner occupancy is required only in the two lowest-density districts. Section 10-8-2(A)(10) provides that within the RR and R-1 zoning districts the owner must use either the primary dwelling or the ADU as their primary residence, and that the two dwellings may not both be occupied unless that is the case. Cody's own administrative ADU checklist carries a matching box asking RR applicants to state whether the owner will occupy the primary dwelling or the accessory dwelling. In R-2, R-2MH, R-3, R-4 and the Mobile Home Park district there is no owner-occupancy condition on the ADU itself, so both units may be leased long term. Note the separate short-term rental rule: R-2 and R-2MH allow an STR only when the owner is living on the property, which is an STR condition rather than an ADU condition. Wyoming has no statute that requires, caps or preempts local owner-occupancy rules, so this is purely local.

Ordinance read August 2026

The review track turns on the zoning district. In RR, R-2, R-2MH, R-3, R-4 and the Mobile Home Park district the ADU is an 'A' use, permitted as an accessory use by right, and the process is administrative: Community Development verifies the zoning, the owner files the ADU checklist with the building permit application, and the Building Department issues the permit under a new ADU address (the city's ADU flowchart and the checklist's staff sign-off block both describe this). No Planning and Zoning Board meeting is triggered, because the pre-permit board review in 9-2-3 reaches only commercial buildings. In R-1 the ADU is a 'C' use and needs a conditional use permit under 10-14-1: a filed application, mailed notice to owners within 300 feet plus newspaper publication 21 days ahead, a public hearing before the Planning and Zoning Board, and a recorded permit; a written protest by owners of 20 percent or more of the lots inside the notice area moves the decision to the City Council and raises the approval threshold to two-thirds.

Ordinance read August 2026

Detached ADUs became legal in Evanston on 3-3-2026, when Ordinance 26-01 added use row 8.1, 'Accessory Dwelling Units,' to the residential use schedule in § 24-15A and enacted a new standards section, § 24-26.1. The answer is zone-dependent: an ADU is a use by right (P8) only in the three Rural Residential districts (RR-E, RR-1, RR-5), it requires conditional use review (C8) in every Low Density Residential district (LR-D, LR-E, LR-E.5, LR-M, LR-M.5), and it is flatly prohibited (an asterisk in the table) in the Medium and High Density Residential districts (MR-E, MR-D, MR-R, HR-E, HR-D, HR-R). Both P8 and C8 point to § 24-26.1, whose 17 standards apply either way. Only one ADU is allowed per lot, only on a lot that already has a detached single-family dwelling, and the lot must either meet the district's minimum lot area or preserve the district's minimum usable open space per dwelling unit.

Ordinance read August 2026

The same use row 8.1 and the same § 24-26.1 standards govern attached, internal and basement units: Ordinance 26-01 defines an accessory dwelling unit as one that 'may be located within, attached to, or detached from the principal dwelling.' So an attached or basement ADU is by right in the RR districts, conditional use review in the LR districts, and prohibited in the MR and HR districts and in every nonresidential district. Attached ADUs must meet the principal-building setbacks for their district rather than the looser accessory setbacks used for detached units (§ 24-26.1A(7)). A basement ADU is the one form exempted from the square-footage cap and may occupy the entire floor area of the basement (§ 24-26.1A(4)(C)). Conversion of an existing lot with a single-family attached or multifamily dwelling is not an option: § 24-26.1A(1) prohibits ADUs on those lots.

Ordinance read August 2026

The review path is set by zone. In the Rural Residential districts (RR-E, RR-1, RR-5) an ADU is a use by right (P8), so approval is administrative: a building permit under § 24-110 plus compliance with the § 24-26.1 standards. In every Low Density Residential district (LR-D, LR-E, LR-E.5, LR-M, LR-M.5) the table shows C8, conditional use review, which means a complete application to the planning office, staff and referral-agency review, and a public hearing before the Planning and Zoning Commission under §§ 24-10 and 24-39 through 24-42, with a City Council call-up available under § 24-11. In the MR and HR districts no permit path exists at all. Separately, because Evanston zones under W.S. 15-1-601 and applies an adopted International Residential Code, the state Fast Track Permits Act (W.S. 16-13-101 and 16-13-102, effective 7-1-2026) now governs the building-permit clock: a completeness notice within 10 business days, a decision within 30 calendar days of a complete application, written denial reasons within 7 days, and deemed approval if the deadline lapses. That act is a processing law only and does not shorten or replace the conditional use hearing.

Ordinance read August 2026

A detached backyard ADU is allowed by right, but only in 5 of the county's 11 base zoning districts and only past real gates. Section 3-1-107(e) makes an ADU 'a permitted use within the URLD, URMD, URHD, MU, and the LU zoning districts', and the definition in 6-1-101 confirms it 'may be an addition to the existing dwelling, be contained within it, or be a detached structure from the principal dwelling', including above a garage. In the rural LU district, which covers most unincorporated land, 3-1-107(e)(ix) bars an ADU on any parcel smaller than two times the AMEC Memo minimum, meaning 10.5 acres against the 5.25-acre base and more inside AMEC zones that require larger lots. In the urban districts (URLD, URMD, URHD, MU) 3-1-107(e)(vii) requires connection to the South Cheyenne Water and Sewer District, so parcels outside that district cannot qualify. This was new law in the 2025 rewrite: the superseded 2022 edition had no accessory dwelling unit at all, only non-rental 'Accessory Living Quarters' for employees or family.

Ordinance read August 2026

Attached and internal ADUs run through the same section and the same gates as detached ones. Section 3-1-107(e)(iv) and (v) allow an ADU to 'be a new structure, or a portion of it' and to 'be an addition to existing principal dwelling', and 6-1-101 allows one 'contained within' the existing dwelling or inside a renovated garage. The conversion must be a genuinely independent unit: 6-1-101(b) and (c) require a separate means of ingress and egress, a kitchen with a sink with running water and a stove or stove hookup, plus living, sleeping, bathing and bathroom facilities, and warn that 'An independent second kitchen by itself within a principal dwelling does not constitute an accessory dwelling unit.' The same district list, the LU acreage gate, and the urban sewer-district requirement apply, which is why this is conditional rather than a flat yes.

Ordinance read August 2026

There is no ADU category, but an attached or internal second unit is possible in some districts because Riverton permits small two-unit buildings. In R-2, § 17.32.010(A) permits 'Multiple-family dwellings containing not more than two living units,' and § 17.32.020(C) caps living units at 'two on any one lot or parcel'; R-2A picks up the same rules because § 17.36.010(C) says all R-2A uses must comply with Chapter 17.32; R-4 goes further and permits multiple-family dwellings 'with any number of living units per building or parcel' (§ 17.40.010(A)). So converting a basement or building an addition into a second self-contained unit is a permitted use in R-2, R-2A and R-4, and in the less restrictive commercial districts by way of § 17.16.100(A)(a). It is not available in R-1, the city's 'limited one-family' district, where a 'one-family dwelling' is defined as 'a building designed exclusively for, and occupied by, one family' (§ 17.08.010); in R-1 the only routes are a rezone by ordinance under § 17.04.050 or a board of adjustment variance under § 17.04.040(G)(3). Check the parcel's district on the city's zoning map before planning anything.

Ordinance read August 2026

A detached accessory dwelling is a principally permitted use, but only in the R-2 Low Density Residential Zone. The § 157.086(B) table of uses lists 'Accessory dwelling' under Residential Accessory Uses with a single entry, 'P (13)', in the R-2 column; the R-E, R-1, R-3, R-4, R-5, R-6 and B-R columns are blank, and § 157.007 provides that any use not expressly permitted or conditionally permitted in a district is excluded. The R-2 purpose statement backs this up: the zone exists for 'single-family detached dwellings, accessory dwelling units and directly related complementary uses.' So the gate is your zoning designation rather than a hearing: check the city zoning map first, because R-1 and R-E, the other low-density single-family zones, do not allow ADUs at all. An owner outside R-2 has only the § 157.224 route of asking the Planning and Zoning Commission to grant an exemption for a use consistent with the district.

Ordinance read August 2026

The zoning ordinance (Appendix A of the City Code) names 'accessory dwelling units' in exactly two places, both added by Ord. No. 2288 of 11-18-2024: the Section 9E Downtown Business Overlay District and the Section 9F Downtown Development Overlay District, where they are Special Exemption Uses requiring review and approval by the Board of Adjustment. No residence district (R-O, R-1, R-2, R-3, R-4) lists an accessory dwelling unit as a permitted use or a special exemption. In residence districts the only habitable backyard building the code contemplates is limited by Section 10.6: a rear accessory building may be used for residence purposes only by a member of the family residing in the main building or by persons employed on the premises, which makes it family or caretaker quarters rather than an independent unit. In the R-O Rural Residence District even that is closed, because an allowed accessory use must not include residential occupancy.

Ordinance read August 2026

There is no attached or internal ADU category, so the question collapses into whether a district permits a second dwelling unit at all. R-1 permits only a 'one-family dwelling', defined in Section 2 as a detached building occupied by one family (which may include up to four boarders or lodgers), so carving an independent second housekeeping unit out of the house turns it into a two-family dwelling and is not allowed there; R-O is the same. R-2 permits a two-family dwelling outright, and a multiple-family dwelling for up to four families in a single detached building, with no minimum lot area per family, and R-3 permits multiple-family dwellings, so an internal or attached second unit is lawful by right in those districts, regulated as half of a duplex rather than as an ADU. In the two downtown overlays one-family and two-family dwellings are permitted except in the story abutting street grade, and accessory dwelling units are a Special Exemption Use.

Ordinance read August 2026

The only use the ordinance calls an accessory dwelling unit is a Special Exemption Use in the two downtown overlay districts, and special exemptions 'shall require additional review and approval by the Board of Adjustment, as outlined in Municipal Code Appendix A, Section 14.' The board holds a noticed public hearing and must find that the exemption is listed for the district, that the use is consistent with the goals, policies and recommended future land use of the adopted master plan, and that granting it is in harmony with the ordinance and not injurious to the neighborhood. Everywhere else there is no ADU application to file: a rear accessory building used as family or caretaker quarters under Section 10.6 needs only the building inspector's permit under Section 12, and a genuinely independent unit in a residence district would require a variance or a rezoning. Since 1 July 2026 the state Fast Track Permits Act shortens the building-permit clock (not the zoning entitlement), because Sheridan zones under W.S. 15-1-601 and adopted the 2024 International Residential Code by Ord. No. 2290 of 1-20-2025.

Ordinance read August 2026