The ADUs of St. Paul … and why aren’t there more of them?

With St. Paul having recently announced plans to once again tinker with its Accessory Dwelling Unit (ADU) ordinance, it seemed like an apt time to try to figure out just how many people have taken advantage of the citywide ADU ordinance passed in late 2018, and to see just what they’ve been building. So, on a recent beautiful Saturday, I set off on my bike in search of the 12 ADUs that have been permitted and built in St. Paul under the rules set in 2018.

According to data obtained from the City 10 of the 12 completed ADUs are detached units, and on my ride I discovered that all but one of them is of the over-the-garage variety. The styles and sizes vary somewhat, but the format is pretty much the same: an alley-loaded garage with an internal staircase up to the second-floor ADU. Alley-side photos sometimes miss interesting features, but here are the public facing sides of St. Paul’s garage ADUs:

A large ADU sits over a detached garage facing with an entrance facing the alley.
At 28×28, a particularly large model.
ADUs may have typical home features, like a deck.
With a ductless mini-split heat pump!
This ADU was able to be built while preserving an existing tree.
Bonus points for preserving the tree.
A modern looking ADU caps a three-car garage.

Three-car garage.
ADUs have the features of their full size counterparts, such as elaborate gables.

Interesting gable details.
Creative garage arrangements can make for large ADUs.

40’x20’ (!), with a side-loading 3-car garage
The footprint for something like a 3 car garage may also require split level floors.

Split level garage floor due to slope
A mostly finished ADU awaits its garage door.

Garage door still to come.
An ADU built into a slope is not as tall from the perspective of the main dwelling.

Built into the slope, so not as tall in the backyard.

The owner of one of these units saw me taking pictures in the alley and graciously offered a tour of her home. She had recently retired from a career teaching in another state, and her ADU was in the backyard of her daughter’s house. She told me it was the perfect solution as it provided the advantages of multigenerational living without everyone having to live under one roof. At 784 square feet, her apartment is a very spacious home for one person and includes a living room, dining room, large kitchen, full bath, washer/dryer nook, pantry, storage closet and a 12’x12’ bedroom. Here are some views of the interior and from the main house:

An ADU with large windows shares a green back yard
A furnished dining area is spacious and indistinguishable from a main dwelling.
ADUs have the same facilities as a main dwelling, such as a complete kitchen with hooded range.
The living room has a balcony and overlooks the shared backyard.

The one detached ADU that was not built over a garage was also designed for multigenerational living. This property, too, had seen the removal of an old garage, but no new garage was built in its place. Instead, the property owner built a backyard bungalow for her parents, who also moved to St. Paul from out of state to be closer to family. The entry to this ADU faces the backyard rather than the alley, and the large building behind the ADU is actually across the alley.

An ADU has replaced a garage, with an entrance facing the backyard.
An ADU with a landscaped garden.

The remaining two ADUs on my tour were attached units, meaning they are attached to the main dwelling. So far, St. Paul does not have any of the third variety of permitted ADUs, which are internal units located entirely within the main dwelling. The first of the attached units was built as an addition onto a bungalow and the other is part of an attached garage:

Other ADUs are attached to the main dwelling.
An ADU with a screen porch is built on top an attached garage.

Data from the City indicates that, in addition to these 13 ADUs, there are five projects that are in some stage of permit review, six properties where the owner either withdrew an application or otherwise suspended or abandoned the project, four that did not progress beyond the inquiry stage, and two properties with pre-2018 structures that were legalized after the fact under the existing rules.
The Planning Commission is currently looking at ADUs as part of its “1-4 Unit Infill Housing Zoning Study,” which is meant to implement housing and land use policies in the City’s 2040 Plan. Goals of the study include “increased housing affordability, diversified housing options, and moderate increases in residential density as ways to address the current shortage of housing and accommodate the next decade of population growth.”

As part of Phase I of the Study, a number of adjustments to the ADU rules have been proposed. These include eliminating the rule permitting ADUs only on lots of at least 5,000 square feet and relaxing the current 800 square feet size limit for ADUs, to allow them to be up to 75 percent of the size of the main dwelling on the property.
These would be positive changes as far as flexibility is concerned, and ADUs are expected to receive further attention during Phase II of the 1-4 Unit Infill Housing Study. But it’s unclear if these changes will result in more ADUs being built. Conversations with architects and ADU owners indicate that the cost of construction is a barrier, if not the primary barrier, to building more ADUs, with the cost of an over-the-garage model (including the garage) typically starting at around $200,000. Detached ADUs are freestanding, fully equipped houses after all, which are made more expensive in Minnesota due to the cost of insulating them.

One architect who has planned ADUs in St. Paul and elsewhere told me that the pace of construction here matches experiences elsewhere, where it has taken time for people to learn about what is now legal and possible. Another design professional told me that people interested in ADUs love to see examples and suggested that an increase in local examples would lead to more ADUs being built. If that’s the case, perhaps an organized ADU bike tour might help spread the word.

About Mark Thieroff

Mark is a land use attorney in Minneapolis. He and his spouse and two sons live, shop, bike and walk their beagle in St. Paul. Twitter: @markthieroff

8 thoughts on “The ADUs of St. Paul … and why aren’t there more of them?

  1. Monte Castleman

    I don’t have any problem with ADUs being allowed to be built, but the low numbers kind of seem to imply that in most cases they aren’t the best solution to any of our problems.

    It’s already legal for your adult kid or mother in law to live in a spare room in your house. No need to spend $200,000 in order to do that. Even if you have to finish off a new room in the basement and add an egress window, you’re probably talking only in the tens of thousands. If you need a bigger house to do it, it’s still probably cheaper and a lot easier to sell your house and buy a bigger one. Or buy a duplex and have your kid or mother in law in the other side.
    It’s also legal to rent out a spare bedroom in your house. Google tells me St. Paul has for a while allowed four unrelated adults to live in a house, now six. By contrast I don’t see how the numbers would possibly work out for short term cash flow in a rental or AirBNB ADU, and if you’re interested in long term appreciation you’re better off just buying another house as a rental.
    What’s left is if you just have to have a relative living on your property, it has to be the property you now own, but you don’t want with them living in your unit or even sharing a wall, you’re willing to invest $200,000, and have a lot of time and wherewithal. It appears these cases are 12 out of 120,000 housing units in the city.

    To hear how some people talked, if only we legalized ADUs, there’s be multiple units on every block and these were going to go a long way to solve our housing shortage. Maybe if builders get used to them and come up with a stock plan that could be dropped on just about any lot the cost could drop some, but probably not significantly.

    1. worknworld

      I think the prefabricated approach would be more cost effective. Especially if most ADUs will be built above a garage. It’s easier to design and manufacture variations built above 2, 3, and 4-car garage models. However, the current number of permits won’t justify much of a manufacturing or design effort.

      1. AndrewS

        I agree pre-fabricated would help speed up the design process, add transparency to costs, and possibly help a wider audience envision an ADU/Garage on their property without having to engage an architect. I’m skeptical however that prefab vs custom built would generate significant cost savings. You’ll still have site-prep, materials/transportation, and the big one for me is digging a trench for water/sewer all the way to the street. I’ve heard it’s possible to get a variance to that requirement and instead tie into the basement services of the main house like how they do in Minneapolis, but they haven’t built all that many over there either so it isn’t like fixing that requirement would spur an influx of new builds.

  2. Jamie Stolpestad

    The biggest barriers are: 1) requirement to bring water and sewer from street vs. house (as allowed in Mpls), 2) requirement to obtain neighbor consent for carriage house type ADU, 3) owner-occupancy requirement and perpetual deed restriction, 4) general cost pressures, especially for small structure in tight quarters. But pre-fab can help. St. Paul’s 1-4 Unit Infill Housing Zoning Study also helpful, please reach out to your City Councilmember to urge passage and bigger steps in next phase. JamieS

  3. Brett Ripley

    As someone who’s waffled on it for years – the headaches / cost of plumbing, specifically drain plumbing have stopped me from doing it. I have the skills to do everything else and would enjoy building an ADU , but digging up my patio and running a drain line across my long backyard, boring through the foundation walls, tyingetc. has kept me from doing it 🙁

  4. Mark Thieroff Post author

    I was definitely one of those who hoped that legalizing ADUs would result in at least a modest increase in housing units and housing density in St. Paul’s residential neighborhoods, and it does seem like things have progressed pretty slowly, although the impact of the pandemic is hard to quantify.

    Regarding the owner-occupancy requirement, just in the past few days planning staff have endorsed eliminating the requirement across the board, and that proposal will be considered tomorrow by the Planning Commission’s Comprehensive and Neighborhood Planning Committee. If that recommendation is well-received, there could be a council vote on it by the end of the year.

    The waste line issue is a head-scratcher. My understanding is that it comes down to how St. Paul’s building official is interpreting the state building code, which happens to be the opposite of how Minneapolis is interpreting it. I would be very interested in hearing from those with relevant experience as to whether/how elected officials can set policy in this area. It seems bizarre that two neighboring cities can arrive at such different intepretations of one rule.

    1. Jamie Stolpestad

      Regarding water / sewer connections, I was told that Minneapolis determined its sewer lines were in poor condition so allows ADUs to connect to the existing main house as the default, while St. Paul has not made such an adverse determination about the condition of its utilities and defaults to requiring new water & sewer service to be accessed from the street. This also creates a potential additional cost of SAC/WAC charges for the new ADU in St. Paul. The logical work-around is for St. Paul to determine its municipal lines are not in perfect shape (and wouldn’t be with tons of new connections) and default to allow an ADU to draw water & sewer service from existing lines to the main house. Maybe after the election noise, PED and DSI could meet and try to forge a practical path forward that reduces costs to homeowners and eases the process of adding an ADU.


    I am one of the people that has been wanting/thinking/wishing I could do this for 20+ years. Was in the planning stages when Covid hit, and am excited about some of the proposed changes to the code to make it a little more accessible and potentially affordable. Also found this company doing some amazing work in partnership with MACV to help house veterans:

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