[Residents] might also ask why the city insists on ever-taller buildings and doubling or tripling density in single-family zones with accessory dwelling units, even though planners say current zoning has plenty of capacity.
So declared the Seattle Times editorial board, parroting one of the most persistent and ubiquitous arguments made during zoning debates far and wide, a rallying cry in neighborhood preservation circles not only in Seattle but in cities across Cascadia and beyond. “We have plenty of zoned capacity” is repeated credulously and earnestly by citizen activists and homeowners at city council meetings and community forums and in online debates (see here, here, here, here, here, here, here, here, here, here).
The zoned capacity argument is also false. It’s a myth. That’s what anyone who carefully looks into the numbers on zoned capacity and the methodology for estimating them can’t help but conclude.
What makes the myth plausible, though, is that zoned capacity—how many new homes could theoretically be built under zoning rules—is a real data point that Seattle and other cities estimate and publish. (You can find it here for Seattle and here for Portland, for example.) And these estimates invariably indicate that there is plenty of zoned capacity to accommodate projected population growth, leading people to wrongly assume that their city is making enough room for newcomers. Reaching that conclusion may be an understandable layperson mistake. For knowledgeable advocates, however, it’s more like malpractice. …
But first, a more important point—in fact, the most important thing to know about zoned capacity: in every city, zoned capacity is a side show to the main event. The main event is housing prices.
Housing prices are the crux of the matter. They reveal if people have enough housing choices. If vacancy rates are low and rents and housing prices are rising, then a city needs more homes. Period. The city needs to remove zoning-code barriers to more housing, so that builders can construct more homes. …
… here’s a summary of the key reasons Seattle’s zoned capacity estimate is misleading and does not justify halting upzones:
- The assessment overestimates zoned capacity. It ignores many real-world obstacles to housing development.
- Most of Seattle’s zoned capacity is in dense commercial areas, which are less family-friendly and more likely to expose residents to air pollution and automobile hazards.
- Seattle’s zoned capacity is shrinking as construction booms. The best building sites are already gone, and others are going fast. The faster a city grows, the sooner it makes sense to upzone and keep plenty of buildable sites available.
- Delaying upzones has the paradoxical effect of reducing future zoned capacity. Every building erected to four stories rather than eight, because zoning is too restrictive, represents four floors of potential homes denied to the city for as much as a century.
- Seattle’s population is growing much faster than projected. …
The numbers are wrong: Why Seattle’s zoned capacity estimate is too high
1. It ignores how buildings actually get built
2. It ignores that Seattle is using up its “lowest hanging fruit” zoned capacity and neglecting future capacity needs.
3. It relies on a too-low population projection.
The values are wrong: Seattle’s zoned capacity does not promote equity
1. The capacity is not zoned as a shared responsibility across neighborhoods.
2. The capacity is not zoned as family-friendly or environmentally just.
… estimating zoned capacity is a theoretical exercise that ignores many of the factors that determine whether or not housing gets built: timeline, fluctuating costs and prices, unwilling sellers and the challenges of parcel assemblage, mismatches between zoning and demand, neighborhood opposition that delays or shrinks or scares away new housing, concentration of zoned capacity in dense districts with worse air and traffic and that are outside of the most desirable neighborhoods.
Zoned capacity also gets consumed by new construction itself, especially when zoning causes smaller buildings with fewer homes to be built, which locks in housing shortages in desired locations for decades. And lastly, in Seattle’s case, the “plenty of zoning capacity” myth implodes not only because the estimate itself is so flawed, but also because the city’s population is growing twice as fast as planners projected.
But as I noted at the outset, zoned capacity is a sideshow, a technical curiosity. Invoking zoned capacity as an argument against more homes for people in Seattle or any other growing city reveals nothing so much as the misunderstanding of those making the argument.