You are traveling through another dimension, a dimension not only of sight and sound but of mind. A journey into a wondrous land of imagination. Next stop, the Thought Experiment Zone!

A few months back I made the case that Minneapolis’ zoning code keeps us from building the type small-scale infill most people say they want (I’m skeptical), or at the very least a scale and intensity that society really likes.

In many cases, the zoning code of today is actually below the existing level of development. This is not by accident. I made the suggestion that if we really want to allow the construction of new (and/or future) affordable housing (lest we become this), everything should be on the table, including relaxing parking minimums and up-zoning. Without major modification to the zoning code, the setback, height and floor area ratio maximums, and other odd requirements make R5 the minimum zoning district to build a modest, historic 5+ unit building by right:

Up-zoning is scary; the thought of massive, neighborhood-wide construction is a doomsday scenario for most (though most seem blissfully comfortable with the scale of redevelopment that allow us all to hop on freeways today). We can’t even replace single family homes with slightly larger single family homes without slamming the brakes.

But I’m a curious man. I’d like to know what it would even look like if we did something totally crazy and up-zoned the whole city to R5 tomorrow. Would the world end? Grab a huge block of salt, suspend your disbelief, and join me on this thought experiment with rough math.

What’s Even Possible?

There’s an idea that was floated around back in 2013: Minneapolis should grow to 500,000 residents by 2025. I tend to agree with the skeptics and question if this goal is even possible – 108,000 new residents in 11 years is indeed a breakneck pace only matched by the decades between 1880-90 and 1900-10. More millennials than you can shake a stick at would make it a struggle to reach that number, and the suburbs will inevitably come calling (but not until you’ve enjoyed your year, of course).

Though not official city policy, it’s probably not a bad idea to spread the city’s mostly fixed infrastructure costs over a larger population (one the city once held). Yet here we are in 2015 with last year’s population estimates topping 411,000, a pace that would put Minneapolis at 489,000 by 2025. So as far as stretch goals go, 500k by 2025 seems good enough for a maximum development potential scenario.

We also know that downtown has a pretty loose regulatory regime permitting dense development without parking in most cases. The Downtown Council conveniently had a goal of doubling the downtown population to 70k by 2025. So we know outside free-for-all downtown, the maximum we could reasonably see Minneapolis growing between 2010 and 2025 is 83,000. Fast-forward to 2025 and the non-downtown gap to 500k is around 70,000 new residents.

How Many New Housing Units?

Ok, so we know we’d need to find room for 70,000 new people in 11 years. One way to bump up population within the city borders is to get average household size on par with the suburbs. According to Met Council data, Minneapolis had 2.35 folks per household vs. 2.55 in “suburban” communities. If some of us have a couple of kids and stick around in the 87,000 mostly under-utilized single family homes currently occupied by aging boomers, that’s capacity for 17,000 new people at suburban family sizes right there.

That leaves 53,000 new people to fill non-existing housing units. They’ll probably mostly go in small-ish apartments and condos. Let’s say the average household size of all new units is 2.13 – the average size of a rented household in 2013 (per American Community Survey data). That’s about 25,000 new housing units by 2025.

Believe it or not, the average units per building (in structures with more than two units) is right around 29, quite a bit higher than I would have expected, though not crazy considering the 2320 Colfax development is 45 units on just over 2 standard lots.

Let’s assume a city-wide R5 re-zone is paired with some stronger rules on lot assembly – no more than 3 standard lots total (120′ of street frontage) and stricter adherence to height (4 stories max) – something nearly every neighborhood organization claims to like. This would limit the scale and bring down the average units per new building; let’s guess 20.

That’s just 1,250 new (net) structures across the whole city (again, excluding downtown) in 10 years’ time. Some developments would replace single family homes, some would be built on empty lots, and some would replace smaller existing apartment, commercial, or (less likely) mixed-use buildings.

Put another way, at an average of 3 lots per redevelopment, probably single family homes, that’s a loss of about 400 structures every year, city-wide. That’s an annual loss just shy of 0.5% of our housing stock. It would take 200 years at this breakneck pace to completely build out the entire city with low-to-mid-rise apartments and condos (ignoring historically protected homes). If you ask me, that’s a pretty slow churn. Some neighborhoods would be hit quicker than others (thinking Lowry Hill, Lowry Hill East, Whittier, and Linden Hills). Even then, tearing down 1-2% a year would be about as aggressive as one could imagine.

Back to Reality

Back in the real world, up-zoning everything, everywhere to R5 probably won’t happen. We’ve got a plan to focus mid-rise construction along (or near) transit lines while soft density via ADUs can enter residential neighborhoods. There are a lot of brownfield sites to go around, too.

However, I do think we should reevaluate some of our zoning choices. Residential districts are far too restrictive (10-12,000 square foot lots for a duplex!?) while not respecting historic form, and we’d be well served to allow commercial uses that serve the “daily use” of residents (similar to German zoning). 500,000 is an arbitrary goal, but it will be difficult to continue growing at a scale many of us will find palatable (especially as commercial/transit corridors become more difficult to redevelop) if we don’t tackle the zoning problem soon.