Thinking about adding a small home above your garage in Longfellow? You are not alone. With many alley lots and classic bungalows, this neighborhood is well suited for garage-top accessory dwelling units that add flexible space or rental income. In this guide, you will learn the main design paths, the rules that shape your layout, cost drivers, and how to move from idea to permit using Minneapolis’ official resources. Let’s dive in.
What makes ADUs legal here
Minneapolis allows accessory dwelling units as a permitted accessory use, including detached units and units above detached garages. The City publishes an ADU application, checklists, and a detailed handout to guide your design and permitting steps. You can review the program on the City’s Accessory Dwelling Unit page and download the application and forms directly from the City’s site. See the ADU application and guidance.
Owner-occupancy requirements have been removed for attached and detached ADUs citywide, which gives you more flexibility in how you use the property. Internal ADUs may still involve a recorded covenant in some cases. You can read the City’s record of this change in the public file. Review the owner-occupancy amendment.
ADUs do not trigger new off-street parking minimums under the zoning code. This is helpful in Longfellow where many garages sit on the alley and space is tight. Check the ADU parking exemption in the code.
Your exact allowances still depend on your property’s zoning district, built-form overlay, and any special overlays. Always look up your lot on the City’s interactive zoning map to confirm setbacks, height limits, and coverage before you draw plans. Open the interactive zoning map.
A building permit is required in addition to the ADU application. If you plan to lease the unit, you will also need a Minneapolis rental license and should budget for licensing fees. The City’s ADU page outlines the general permit path, and the rental license page covers fees. See the ADU program overview and rental license fees.
Key code rules that shape design
Minneapolis provides a concise handout that translates building code into garage-top ADU specifics. Design choices and costs often come down to these items. Download the City’s key code requirements PDF.
Foundations and frost protection
- Habitable units must sit on frost-protected footings. Many older detached garages in Longfellow were not built with frost footings.
- Converting an existing garage often requires new or engineered footings, which can be a major cost driver.
Fire separation near lot lines
- Walls and eaves within 5 feet of a side lot line generally need a one-hour fire-rated assembly.
- Openings like windows and vents are typically not allowed within 3 feet of a side property line. Eaves cannot extend closer than 2 feet. The alley side can be treated differently in some cases.
Separating garage and living space
- If you keep parking below, the floor/ceiling between the garage and dwelling must be a one-hour fire-rated assembly.
- Provide a fire-rated door where required, R-30 insulation between spaces, and a dedicated exit for the living unit that does not route through the garage unless fully rated.
Ceiling height, stairs, and egress
- Minimum ceiling heights for habitable rooms are 7 feet.
- Stair width, headroom, risers, and treads must meet code, and sleeping rooms need compliant egress windows.
- These rules determine how much usable area you get under a gable or shed roof and where stairs can go.
Mechanical and plumbing
- The ADU must have independent ventilation and HVAC from the garage.
- A plumber or engineer should confirm water and sewer service sizing. Undersized lines may need to be upsized.
- Gravity connections are preferred for sewer. Pumped systems are limited and need freeze protection.
Height and built form
- The City amended accessory structure height rules to allow taller accessory buildings in some cases, but your built-form overlay and zoning plate still control height and coverage. Learn about accessory structure height standards.
Four design paths for above-garage ADUs
Convert an existing second story
Pros:
- Often the lowest-cost path if the structure is sound.
- Preserves your footprint and can move faster through permits.
Watch-outs:
- Many older garages lack frost footings and need foundation work.
- You must provide a one-hour separation and a separate exterior exit.
- Low roof pitch or headroom can limit usable square footage.
Build a new carriage house
Pros:
- Full control over roof pitch, insulation, layout, and ceiling heights.
- Combines secure parking below with a well-designed living space above.
Watch-outs:
- Higher construction costs and valuation-based permit fees.
- You still must meet setbacks and fire rating rules near lot lines.
Attach an ADU above an attached garage
Pros:
- Utility connections can be simpler depending on layout.
- May leverage the main home’s foundation and structure.
Watch-outs:
- Code treatment differs for internal, attached, and detached units. Internal ADUs may involve an owner-occupancy covenant.
- Confirm details early with the City’s ADU guidance and your design team.
Hybrid tweaks and add-ons
Pros:
- You can extend an existing second floor or create a compact studio above part of the garage.
Watch-outs:
- The same checkpoints apply: frost footings, egress, mechanical separation, and minimum ceiling heights.
Longfellow-specific design tips
Longfellow’s blocks feature early 20th-century bungalows, foursquares, and compact lots with rear alleys. That context affects both design and neighbor expectations.
- Place your main ADU entry off the alley or rear yard where practical. Many lots already function this way in Longfellow.
- Reduce visual bulk from the street by matching roof forms and siding to the main house and by limiting eave projections near property lines.
- Set windows to respect privacy where buildings sit close together, and use opaque glass where code allows.
- If you want neighborhood input or to understand local priorities, connect with the Longfellow Community Council. Visit the Longfellow Community Council.
Costs, timelines, and permits
Budget ranges vary by scope, finishes, and whether you need foundation work or utility upgrades. For a garage-top ADU or new carriage house, a broad range runs from tens of thousands for very modest work to roughly $150,000 to $350,000+ for a well-finished, code-compliant unit with full trade upgrades. See a national overview of ADU costs.
Common cost drivers:
- New frost footings or engineered foundation solutions.
- Electrical service upgrades to support an additional dwelling unit.
- Water and sewer line upsizing and rerouting.
- Required one-hour fire separations and exterior stair or entry work.
Timeline expectations:
- Plan for design, plan review, permits, trade inspections, and final occupancy. Duration depends on complexity and City workloads.
- If you intend to lease the unit, factor in the time and fees for a rental license. Review rental license fees.
As of October 2025, the City’s ADU application and handouts are your best starting point for current rules, submittal checklists, and process steps. Start with the City’s ADU page.
Step-by-step next steps
- Check feasibility
- Look up your address on the City’s interactive zoning map to confirm zoning and overlays. Open the interactive zoning map.
- Learn the code basics
- Download the City’s detached ADU key requirements to understand frost footings, fire separation, egress, and mechanical rules. Get the code requirements PDF.
- Talk with the City
- Use the ADU application page to review checklists and contact CPED or 311 with address-specific questions. Visit the ADU program page.
- Scope your design and budget
- Have a design professional assess foundation conditions, electrical capacity, and water-sewer sizing so your plans and estimate match code realities.
- Engage the neighborhood
- If desired, connect with the Longfellow Community Council for context and to learn about block-level preferences. Explore the Longfellow Community Council.
Ready to plan your next move
Whether you are evaluating a property with ADU potential or thinking about resale after a project, a clear plan helps you protect value. If you want to discuss how an above-garage ADU could play into your buying or selling strategy in the Twin Cities, reach out to Julie Doolittle for local, step-by-step guidance.
FAQs
Can you build an ADU above a detached garage in Longfellow?
- Yes, if your lot allows an ADU under zoning and you meet building code requirements. Start by checking your address on the City’s interactive zoning map and reviewing the City’s ADU handouts.
Do you need to live on-site to add a detached ADU in Minneapolis?
- No. Minneapolis removed owner-occupancy for attached and detached ADUs. Internal ADUs may still involve a recorded covenant, so confirm details in the City’s guidance.
Will an ADU require you to add more off-street parking?
- No. The zoning code exempts ADUs from additional minimum off-street parking. Site realities and neighbor considerations may still guide your design.
What are the biggest hidden costs for a garage-top ADU?
- Foundation work for frost protection, electrical service upgrades, water and sewer upsizing, one-hour fire separations, and exterior stairs or entries commonly add cost.
How tall can a new carriage house be in Minneapolis?
- Accessory structure height allowances have been relaxed in some cases, but your built-form overlay and zoning plate control the exact limit on your lot. Verify on the City’s zoning map and height standards pages.
How long does permitting take for an ADU?
- Several months is common from feasibility to occupancy, depending on design complexity and City review timelines. Plan for multiple trade permits and on-site inspections before final sign-off.
