Missoula’s rules allow a primary residence and one accessory structure (ADU, garage, workshop, etc.) to share a water service line, but only if there is adequate capacity as determined by the Uniform Plumbing Code (UPC). UPC requires a fixture count to be completed for all fixtures that will receive water from the shared service line (i.e. including the existing primary structure and the accessory structure). Most existing water service lines in Missoula are ¾” galvanized pipes and very rarely (if ever) will a ¾” line meet the total fixture count demand of a house plus an accessory structure. In addition, many existing galvanized service lines are already beyond their expected useful life and should be evaluated for replacement. Anyone planning to build an accessory structure on a property with only a single ¾” service line should plan to replace the service with a modern 1-inch polyethylene (PE) service.
Note that two primary residences on a single parcel will always be required to have separate services. Any future subdivision or townhome creation will also require separate services for each lot or townhome.
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No, ADUs do not require additional parking.
Yes, currently there is. They can be found here, in Title 20, 20.45.060 – Accessory Dwelling Units.
No, that law is no longer in effect.
No, if the structure meets all zoning ADU standards and the permit is approved, the applicant can proceed with construction. There is also a requirement that applicants submit a notarized statement that the ADU does not violate any neighborhood covenants. The city does not keep, nor enforce neighborhood covenants.
After you have confirmed your parcel to have met the criteria, you may want to contact a design and/or land use professional.
You can also reach out to firstname.lastname@example.org and schedule a Project Review Team (PRT) meeting, which is a one-hour virtual meeting with the planning, engineering and building departments to determine a project’s feasibility. Please submit a permit intake form, which can be found here, along with a site plan, design details and list of questions.
Yes. An ADU can share utility infrastructure with a primary residence. The infrastructure must have the capacity to handle an additional dwelling unit. The property owner should contact utility agencies (natural gas, electricity, water, sewer) for information about utility requirements.
Development Services can determine the status of a dwelling unit and whether the general standards of the zoning district or the nonconforming uses standards apply. If the second dwelling unit is illegal, building permits must be obtained retroactively to make the unit legal.
In Missoula, the homeowner owns and is responsible to maintain the water and sewer services lines from the point of connection at the main (typically in the street or alley) all the way into the house or structure.
Accessory structures are not allowed on properties that have flat rate accounts. If you want to add an accessory structure, you will need to install a meter on the service line for the primary residence. You will need to read the other FAQ’s on this page which deal with sharing service lines and meters.
Missoula’s rules allow a primary residence and one accessory structure (ADU, garage, workshop, etc.) to share a sewer service line, but only if there is adequate capacity as determined by the Uniform Plumbing Code (UPC). UPC requires a drainage fixture count to be completed for all fixtures that will contribute drainage to the shared sewer service line (i.e. including the existing primary 2 structure and the accessory structure. The sewer service line would need to be a minimum of 4” in diameter.
The City of Missoula has electronic ditch cards for both water and sewer services available for most addresses. These are being made available on the City of Missoula Public Utility Map located on www.MissoulaMaps.com. If you can’t find your water ditch card at that website, you can contact Missoula Water dispatch at: email@example.com. If you can't find your sewer ditch card at that website, you can contact the Public Works & Mobility Engineering department at: firstname.lastname@example.org.
The City of Missoula has required a tool to assist with calculating water supply fixture counts for residential properties. Guidance for completing water supply fixture counts for commercial applications and drainage fixture counts for all applications is provided in the UPC. Any questions about fixture counts can be directed to Tony Sauro, the City’s plumbing inspector, at (406)239-1385.
No, Missoula Water does not require a separate meter for an accessory structure , as long as the accessory structure’s water service is connected downstream of the meter for the primary residence. Missoula Water recommends that a separate curb box be installed on the line serving the accessory structure so that it can be shut off in the event of a leak.
: Yes, the customer can choose to install a separate water meter in a pit for a new accessory structure. If the customer chooses to install a separate meter, curb boxes must be installed that will allow each meter to be shut off independently, or a separate line to the main can be installed for the accessory structure. The meter pit and curb box should be placed as shown in the Typical Residential Water Service Detail (WSD-2).
The customer should be aware of the costs associated with metering the accessory structure separately, including the cost of installing the pit and curb boxes that will allow each account to be shutoff separately, the additional monthly fixed charge for the water meter, and the additional sewer development fee that is charged for each meter. In the future Missoula Water is also planning to institute a water development fee that will be charged for each meter.