Plymouth allows ADUs by right through an administrative permit under City Code §21190.04. Ordinance No. 2024-22 and Ordinance No. 2026-01 significantly expanded eligibility, from newer subdivisions only to essentially all single-family homeowners citywide.
Last verified: August 20266/10 · Moderate
700 sq ft*
Max ADU size
Match house
Max height
Required
Owner-occupancy
By-right
Permit type
This page summarizes Plymouth City Code §21190.04 (Accessory Dwelling Units), as amended by Ordinance No. 2026-01 (adopted February 10, 2026) and Ordinance No. 2024-22 (adopted September 24, 2024), for general reference - it is not legal advice. Regulations change; always confirm current requirements with Plymouth's Inspections Division before designing or applying for permits. See sources below.
Zoning & size requirements
What you're allowed to build
ADU type
Max size
Max height
Notes
Detached
700 sq ft, or 30% of the rear yard area, whichever is less (minimum 200 sq ft)
May not exceed the height of the principal dwelling (City Code §21120)
Set back at least 20 ft from an alley if the accessory building has direct vehicular access onto it; other setbacks follow your specific zoning district's standards. In the FRD district, a detached accessory building may exceed the standard size caps with a conditional use permit.
Attached / internal
1,000 sq ft, or 30% of the primary home's floor area, whichever is less
Same as principal dwelling
-
Allowed zoning districts
FRD and RSF (single-family) districts, and single-family detached dwellings in RMF and PUD districts. Historically ADUs were limited to newer subdivisions in Plymouth; Ordinance 2024-22 (Sept 2024) and Ordinance 2026-01 (Feb 2026) expanded eligibility to essentially all single-family homeowners citywide.
Additional standards
Setbacks, parking & other rules
Setbacks & height
Detached ADUs may not exceed the height of the principal dwelling and must sit at least 20 ft from an alley if accessed from one; other setbacks follow your specific zoning district's standard accessory-building rules (City Code §21120)
Parking
No additional off-street parking is required - an early draft of the ordinance included this requirement, but the Planning Commission removed it before adoption
Owner-occupancy
Required, confirmed by multiple local news sources
Short-term rentals
Banned (Airbnb/VRBO-style). Long-term rental of the ADU is allowed.
Units per lot
Typically one ADU per lot. Not explicitly confirmed in available sources, but consistent with every other Twin Cities city researched.
Permit process
Standard building/inspection permitting through the Inspections Division; no ADU-specific fee schedule was found
Ordinance history
How Plymouth's ADU rules got here
2023Planning Commission recommends citywide expansion. Until this point, Plymouth's ordinance allowed ADUs only above attached or detached garages, and only on the city's newest residential lots - those platted after 2001 in subdivisions of 10 or more lots. That June, the Planning Commission approved a policy recommendation to open eligibility to all single-family property owners.
2024Ordinance 2024-22. Adopted September 24, 2024, this amendment significantly expanded ADU eligibility beyond the newer-subdivision restriction.
2026Ordinance 2026-01. Adopted February 10, 2026, this further amendment extended ADU eligibility to essentially all single-family lots citywide, under the size caps shown above.
Plymouth's planning director told local media in 2023 that the city was "getting more and more calls for this as housing prices, interest rates, construction costs continue to go up" - part of why the city moved to open ADUs to essentially all single-family homeowners after years of limiting them to a narrow slice of newer subdivisions.
Permit process
How Plymouth ADU permitting works
1
Confirm eligibility
Verify your property is in the FRD or RSF district, or is a single-family detached home in the RMF or PUD district.
2
Prepare your plan set
Put together a site plan, floor plans and elevations of the ADU, and - for attached or internal units - floor plans of the existing home so staff can confirm the 30%-of-home size calculation.
3
Submit administrative permit application
ADUs are reviewed administratively under City Code §21190.04, not through a discretionary conditional use permit process.
4
Plan review
Reviewed by the city's Inspections Division for zoning and building code compliance. Submit a PDF application and plan set to inspections@plymouthmn.gov.
5
Building permit & inspections
Complete the standard building, plumbing, electrical, and mechanical inspection process before occupancy.
6
Rental license (if renting long-term)
Short-term rental of the ADU is banned, but long-term rental is allowed - confirm whether Plymouth's rental dwelling license requirements apply to your property before placing tenants.
No ADU-specific permit fee schedule or review timeline was found in available sources at time of writing - confirm current figures with the Inspections Division at 763-509-5430 or inspections@plymouthmn.gov.
Budgeting
What it costs to build an ADU in Plymouth
Garage conversion
Roughly $65,000-$160,000, the least expensive path since the shell already exists
Basement conversion
Roughly $110,000-$220,000, depending on existing ceiling height and utility access
New detached ADU
Roughly $135,000-$300,000+ for a code-compliant, fully insulated freestanding unit, though Plymouth's 700 sq ft detached size cap will tend to keep new detached units toward the smaller, less expensive end of that range
SAC fee
$2,485 per unit in 2026, charged by Metropolitan Council Environmental Services on new units that add sewer demand
City permit & plan review fees
No ADU-specific fee schedule was published; Plymouth's standard building permit fee is valuation-based - get a project-specific quote from the Inspections Division before you budget
These are general ranges from local contractor estimates and regional reporting, not quotes - Plymouth-specific cost data wasn't publicly available, so treat these as starting points, not precise figures. Actual cost depends heavily on lot conditions, finishes, and whether utilities need to be extended. Minnesota's climate adds real cost too: a detached ADU is a fully insulated, freestanding structure, not just a room.
Before you apply
Tips for a smooth approval
Don't assume the old newer-subdivision rule still applies. Plymouth restricted ADUs to lots platted after 2001 for years - if you looked into this before 2024 and were told no, it's worth checking again under the current, much broader rule.
Design to the right size cap for your ADU type. Detached units top out at 700 sq ft (or 30% of the rear yard, if less); attached or internal units can go up to 1,000 sq ft (or 30% of the home). Mixing up the two numbers is an easy early mistake.
Plan to live on site. Plymouth requires owner-occupancy and bans short-term rental of the ADU, so this isn't a fit if your goal is an Airbnb-style investment property.
Confirm you're working from the current ordinance. Plymouth's ADU rules changed twice in under two years (2024 and 2026) - double-check with the Inspections Division that your plans reflect Ordinance 2026-01, not an older version.
Ask about parking directly, rather than assuming. Reporting suggests an earlier proposed additional-parking requirement was dropped, but this wasn't independently confirmed - get a straight answer from the city before you finalize your site plan.
FAQ
Common questions
Do I need to live on the property to build an ADU in Plymouth?
Yes. Owner-occupancy is required, per multiple local news sources covering the ordinance.
Can I list my ADU on Airbnb?
No. Short-term rentals of ADUs are banned in Plymouth. Long-term rental of the ADU is allowed.
What's the size difference between detached and attached ADUs?
Detached ADUs are capped at 700 sq ft (or 30% of the rear yard, whichever is less). Attached or internal ADUs are capped at 1,000 sq ft (or 30% of the primary home's floor area, whichever is less).
Which properties qualify?
Historically, Plymouth limited ADUs to newer subdivisions - lots platted after 2001 in subdivisions of 10 or more lots, and above-garage units only. Ordinance No. 2024-22 (adopted September 2024) and Ordinance No. 2026-01 (adopted February 2026) significantly expanded eligibility, so ADUs are now allowed on essentially all single-family lots in the FRD and RSF districts, plus single-family detached homes in RMF and PUD districts.
When did Plymouth start allowing ADUs citywide?
Not until recently. Before 2023, Plymouth's ordinance allowed ADUs only above garages, and only in newer subdivisions platted after 2001. The Planning Commission recommended opening eligibility to all single-family owners in 2023, and the City Council followed with Ordinance 2024-22 in September 2024 and Ordinance 2026-01 in February 2026.
How much does an ADU cost to build in Plymouth?
It depends on the project type. Based on local contractor estimates and regional reporting (Plymouth-specific cost data wasn't publicly available), garage conversions tend to run roughly $65,000-$160,000, basement conversions $110,000-$220,000, and new detached units $135,000-$300,000 or more - though Plymouth's 700 sq ft detached size cap will tend to keep a new detached unit toward the smaller, less expensive end of that range. None of this counts the $2,485 SAC fee or permit costs.
What documents do I need for the permit?
Expect to submit a site plan, floor plans and elevations of the ADU, and - for attached or internal units - floor plans of the existing home so staff can confirm the 30%-of-home size calculation.
What are the city's ADU permit fees?
No ADU-specific fee schedule was found in available sources. Plymouth's standard building permit fee is valuation-based; get a project-specific quote from the Inspections Division at 763-509-5430 or inspections@plymouthmn.gov.
Do I need extra parking for an ADU?
Uncertain. Earlier drafts of the ordinance required an additional off-street parking space; later reporting suggests the Planning Commission dropped that requirement from subsequent drafts, but the final adopted rule wasn't independently confirmed. Confirm current parking rules with the Inspections Division before you design.
