ADU rules in Whitefish

Whitefish City Code 11-3-1.B allows an ADU detached from the primary single-family dwelling, attached to it, or attached to a garage on the same lot. ADUs are a listed permitted accessory use in every residential, resort residential, and resort business district and in the WB-1, WB-2, WB-3, WBSD, WT-3, WB-T, and Big Mountain districts (for example 11-2F-2 for WR-1), always accessory to a single-family dwelling. Ord. 23-22 (10-16-2023) brought the section into conformance with MCA 76-2-345 and deleted the former 26-foot height cap for detached ADUs; under 11-3-2.B a detached ADU is exempt from the 24-foot height limit that binds other residential accessory buildings.

Attached and internal ADUs are equally allowed. The 11-9-2 definition recognizes an Attached type covering converted living space in basements and attics, attached garages, and additions, alongside the Detached type (converted detached garages, new cottages, living space over garages), and 11-3-1.B covers units attached to the dwelling or its garage. Only one ADU or guesthouse is permitted per lot, and the primary use must be a single-family dwelling.

11-3-1.B caps the ADU's interior habitable floor area at 1,000 square feet or 75 percent of the primary structure's gross floor area, whichever is less, exactly the MCA 76-2-345(1)(c) ceiling. Ord. 23-22 (10-16-2023) raised the cap from the former 600 square feet (800 with a deed-restricted long-term lease) and deleted the old 26-foot, two-story limit for detached ADUs; a detached ADU is now exempt from the 24-foot accessory-building height cap (11-3-2.B) and follows the district's primary-structure height. Accessory buildings with a footprint over 600 square feet must meet primary-structure setbacks, while 600 square feet or less qualifies for reduced 6-foot side and rear setbacks under the district standards tables.

No owner-occupancy requirement appears anywhere in Title 11: not in 11-3-1, the district use lists, or the short-term rental standards (full-text check of the codified title on 2026-08-04). MCA 76-2-345(2)(c) forbids Montana municipalities from requiring that the single-family dwelling or the ADU be occupied by the owner, and Whitefish's SB 528 conformance ordinance (Ord. 23-22) left no such condition. Either unit may be rented while the owner lives elsewhere.

11-3-1.E states that no off-street parking beyond what the primary dwelling already requires may be demanded for an ADU. The former one-space ADU requirement was deleted by Ord. 23-22 in 2023, matching the MCA 76-2-345(2)(a) parking prohibition. The MLUPA rewrite of Title 11 (Ord. 26-06, adopted 6-1-2026, effective about 7-1-2026, still pending codification) adds an explicit Accessory dwellings row reading no required parking for the accessory dwelling unit to the 11-6-2 parking table and cuts general residential parking to 1 space per dwelling unit, with none required for residential units under 1,200 square feet.

ADUs are listed permitted uses in their districts and are reviewed through a standard building permit; the city's ADU Quick Guide states a building permit must be obtained before starting construction or renovations, and no conditional use permit or public hearing applies. Converting existing space to an ADU without construction that needs a building permit requires an administrative zoning compliance permit from the zoning administrator (11-7-9), decided within 20 business days. MCA 76-2-345(1)(a) independently guarantees by-right review, defined in (9)(b) to exclude hearings, variances, conditional use permits, and other discretionary action.

An ADU may be rented long term (11-3-1's stated purpose includes a supplemental income stream for owners of residential property), but it may never be sold separately from the primary home (11-3-1.C). Short-term rental, defined in 11-9-2 as stays under 30 days, is a separately zoned use: 11-3-35 confines STRs to specific districts (the city lists WB-3, WRR-1, WRR-2, WRB-1, and WRB-2; the Big Mountain Village district's use list also includes short term residential rentals) and requires an STR registration and business license (400 dollars per year per the city), an annual fire inspection, a state public accommodation license, and monthly resort tax remittance. Advertising an unpermitted STR is itself evidence of a violation, with fines of 300 to 500 dollars per day. MCA 76-2-345(3) expressly preserves this local STR regime, the best known in Montana.