All Roll Calls
Yes: 322 • No: 72
MontanaSB 53269th Legislature, Regular Session (2025)SenateWALLET
Revise county zoning to allow accessory dwelling units
Sponsored By: Forrest Mandeville (Republican)
Signed by Governor
PlanningCountiesEnvironmental ProtectionHousingLocal GovernmentRevenue, LocalRevenue, State
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Bill Overview
Analyzed Economic Effects
6 provisions identified: 4 benefits, 1 costs, 1 mixed.
Homeowners can add one ADU by right
If your lot has a single-family house in a zoned county, you can build one accessory dwelling unit (ADU) by right. Approval does not need a public hearing or variance, only a site plan check for zoning. The ADU can be attached, detached, or inside the main home. Until counties update local rules, they must use these state standards. An ADU is a self-contained unit on the same parcel with its own kitchen, sleeping, and bathroom, and it must meet safety rules or be exempt.
Lower upfront ADU fees
Counties cannot charge impact fees for an ADU. They can charge at most $250 one-time per ADU application, plus normal building fees.
No owner or tenant rules for ADUs
Counties cannot require the owner to live in the main house or the ADU. They also cannot require ADU tenants to be family, married to, or employed by the main house occupants. Owners can rent either unit to anyone.
Simpler ADU design and zoning standards
Counties cannot force an ADU to match the house’s exterior, roof angle, or materials. ADUs cannot face stricter height, setback, lot size, coverage, or frontage rules than the main house. Counties cannot add tougher ADU rules beyond this law or require a restrictive covenant to get a permit. Counties also cannot require street upgrades for a permit, but they can require repairs if your ADU work damages a public street.
15-day sanitation review for ADUs
If your lot has public water and sewer with capacity, the Department of Environmental Quality gives a 15-day expedited sanitation review for your ADU. Some changes to connect to city or county water or sewer can proceed with streamlined review. These faster options end on September 30, 2029.
Safety codes and rental limits apply
Building, fire, and public health rules still apply to ADUs. Counties can still make rules for short-term rentals. Short stays in an ADU may be limited by local rules.
Sponsors & Cosponsors
Sponsor
Forrest Mandeville
Republican • Senate
Cosponsors
There are no cosponsors for this bill.
Roll Call Votes
Senate vote • 4/28/2025
Do Pass
Yes: 47 • No: 2
Senate vote • 4/25/2025
Do Pass
Yes: 45 • No: 4
House vote • 4/23/2025
Do Concur
Yes: 75 • No: 24
House vote • 4/22/2025
Do Concur
Yes: 76 • No: 24
Senate vote • 4/5/2025
Do Pass
Yes: 41 • No: 7
Senate vote • 4/4/2025
Do Pass
Yes: 38 • No: 11
Actions Timeline
Chapter Number Assigned
5/16/2025SenateSigned by Governor
5/13/2025SenateTransmitted to Governor
5/5/2025SenateSigned by Speaker
5/5/2025HouseSigned by President
5/2/2025SenateReturned from Enrolling
4/29/2025SenateSent to Enrolling
4/29/2025Senate3rd Reading House Amendments
4/28/2025Senate2nd Reading House Amendments
4/25/2025SenateReturned to Senate with Amendments
4/23/2025House3rd Reading
4/23/2025House2nd Reading
4/22/2025HouseCommittee Report
4/16/2025HouseCommittee Executive Action
4/15/2025HouseHearing
4/7/2025House1st Reading
4/7/2025HouseReferred to Committee
4/7/2025HouseTransmitted to House
4/5/2025Senate3rd Reading
4/5/2025Senate2nd Reading
4/4/2025SenateCommittee Report
4/3/2025SenateCommittee Executive Action
4/2/2025SenateHearing
3/27/2025SenateReferred to Committee
3/20/2025Senate1st Reading
3/18/2025Senate
Bill Text
Enrolled
4/29/2025
As Amended (Version 3)
4/16/2025
As Amended (Version 2)
4/3/2025
Introduced
3/18/2025