How Much Does it Cost to Build an ADU?

There’s something very appealing to having a fully-functional, separate living space on your property. Whether you call it a granny flat, mother-in-law suite, or an above garage apartment—ADUs (Accessory Dwelling Units) are taking the Twin Cities by storm.

The most popular type of ADU is an apartment over a garage. But to be honest, people are usually shocked by the cost, wondering why we can’t simply stick a second level on top of an existing garage. Since these are such popular projects for people to ask about we thought we’d break those costs down with two actual projects to help people understand. The first, a fully-functional, finished studio apartment above a new garage in South Minneapolis. The second, an unfinished ADU (structure only) in St Paul, that the homeowner will finish on their own.

To put this into perspective, both of these ADUs are pretty modern and awesome, but they are both on the lower-end when it comes to budgets that we put together for these types of projects.

ADU #1: Fully Finished Studio Apartment Over a Garage

Total cost including design & construction: $325,000 and completed in 14 weeks!

  • 22’x22’ Garage
  • 22’x24’ Studio Apartment Above
  • ¾ Bath With Laundry
  • Granite Countertops
  • Kitchenette (Includes Cooktop, But No Oven) + Dishwasher
  • Exterior Staircase



Here’s the breakdown:

1. Design, planning, permits, set up, and project management fees (including demolition, dumpster, satellite toilet, and clean up) $50,000

The best part about working with a design-build company is they take care of everything. Our team worked with this client on the design, weighing the benefits of open floor plans vs. adding walls, and how that would impact the space. We recommended fixtures and finishes that matched their style (and budget) while incorporating any unique elements that came up. We also jumped through all the hoops with the city to make sure all permits were taken care of (which can be extra tricky with ADUs), ensuring that building this ADU went off without a hitch!

On time and on budget, and keeping you in the loop every step of the way, this is the project manager’s job, and it’s essential in every White Crane project. Project managers coordinate with all of the trade partners, from demo to all the finish work. For this ADU, the homeowner was pleasantly surprised by the near-daily communication throughout the process.

2. Structural engineering fees $2,650

Every project is engineered to be rock solid. A lot of people interested in ADUs are surprised that they typically can’t use their existing garage, but unfortunately, traditional garages aren’t built with the proper foundation that would prevent settling with a significant structure built on top of it. The final plans will be engineered to make sure your renovation is structurally sound.

3. Construction Costs $272,350

An ADU is like building a small house. Construction costs include demolition of the old garage, excavation, framing, electrical, plumbing, heating/cooling, insulation, windows, doors, siding, drywall, carpentry, custom cabinets – this is where a majority of costs come in. Every ADU requires several trade partners (subcontractors) to pull this off. At White Crane, we’ve been in business long enough to know that it pays to work with the best partners. And those partners appreciate us too. We firmly believe finding the best people and keeping them busy will produce better results, faster. You’ll love our trade partners because they love what they do, they’re trustworthy, and they’re masters of their craft.

Here is a breakdown of total construction costs:

  • $172,000 Foundation, Framing, Rough Carpentry, Mechanicals (plumbing, heating, ventilation, cooling, electrical) – Electric, water, sewer… every ADU is a little different. In Minneapolis, ADUs are required to tie into the primary home’s water/sewer. For this project, we had to trench into the homeowner’s finished basement, which added costs outside of the typical range. Every remodel has hidden surprises like this, but fortunately, we do our work upfront and everyone was aware of this part of the project before we started.
  • $51,450 Exterior Doors, Windows, Insulation, Exterior Finishing (siding, roofing, trim, gutters)
  • $10,400 Cabinetry, Countertops
  • $6,600 Flooring (Hardwood, Carpet, Vinyl, etc.)
  • $28,000 Finishes (drywall, finish carpentry, tile, paint, closet systems)
  • $3,900 Plumbing Fixtures, Light Fixtures, Cabinet Hardware, Accessories, Mirror, Shower Glass


ADU #2: New Garage with Unfinished Second Level

Total cost including design & construction: $205,400 and completed in 6 weeks!

  • 22’x22’ Garage
  • 22’x24’ Living Space Above (unfinished interior)
  • Exterior Staircase



Here’s the breakdown:

1. Design, planning, permits, set up, and project management fees (including demolition, dumpster, satellite toilet, and clean up) $48,100

2. Structural engineering fees $2,600

Similar to most ADUs, we had to start from scratch by tearing out the old one-car garage to ensure the proper foundation to avoid settling. The final plans ensured this was structurally sound, and considered how to build a significant structure in such a tight space.

3. Construction Costs $154,700

Even though this is an unfinished ADU, it still requires everything needed to build a small house, but without the finish work upstairs. The construction costs for this ADU included; demolition of the old garage, excavation, framing, electrical finished in the garage and roughed-in upstairs, plumbing rough-in to the garage, insulation, windows, doors, siding, drywalling the garage but not the upstairs, and exterior steps. We worked with our trade partners (subcontractors) to complete much of the work. All of our partners are trustworthy, masters of their craft, and quality pays off in both the short and long-term.

Here is a breakdown of total construction costs:

  • $122,850  Foundation, Framing, Rough Carpentry, Rough-ins & Utility Connection – Since this ADU wasn’t going to be finished by White Crane, some of the utility connections would be completed at a later date. For the electrical, the biggest challenge was the original power line was set up for a single-story garage. To solve this issue, Xcel Energy ran a new line to the garage, and we buried the electrical for the house in the backyard. ADUs also require a separate electric panel so we made sure that was hooked up, and the upstairs electrical was roughed in, but no fixtures were installed. The water/sewer was only run to the lower level of the garage after digging a trench in the backyard in order to tie into the main home’s water/sewer.
  • $27,300  Exterior Doors, Windows, Insulation, Exterior Finishing (siding, roofing, trim, gutters)
  • $1,300 Materials to restore the basement bathroom in the main house after connecting plumbing from home to ADU
  • $2,730  Finishes (drywall, paint)
  • $520  Exterior Light Fixtures & Hardware

While these two specific projects are more on the entry-level side, ADU pricing can jump up quite a bit from there. Options like interior steps, or higher-end finishes (to name a few things) would increase the budget. While those options won’t add exponentially to the cost, it doesn’t take much to get into the $300K range.

If you have other questions on ADUs, feel free to contact us, we’re happy to answer any questions or put you in touch with homeowners who recently built ADUs. Most of them are utilizing their ADUs to generate revenue through short-term rentals, which end up offsetting most, if not all, of the costs.

Want to learn more about the process of building a finished ADU? Look inside building this garage apartment in Minneapolis.

Want to learn more about building an ADU with an unfinished second level (structure only)? Look inside this unfinished ADU structure we built in St. Paul.