Web Map: Affordable Housing Not Allowed Here

The New York Times just published a great new article with interactive maps that's fast making the rounds among planners and smart growth advocates:

Cities Start to Question an American Ideal: A House With a Yard on Every Lot

Rising concerns about housing affordability, racial inequality and climate change are causing cities nationwide to re-examine their attachment to the detached house.

→ Read full article here

The article describes how many U.S. cities have created zoning codes that exclude more affordable types of housing (townhomes, duplexes, etc.) from significant swaths of city land.

How does Bozeman stack up? Better than many communities, though still with a significant portion of the city's residential land dedicated to detached single-family houses. Based on the figures in Bozeman's 2018 Land Use Inventory Report some 41% of residential land in Bozeman has a zoning designation for single family residences (R-S and R-1).

Curious about how Bozeman compares, I put together a map combining city parcels and zoning. The map of Bozeman below shows areas that are zoned exclusively for single-family residences in pink. Areas that allow other types of housing are shaded in blue:

The map above shows multi-family zoning only where zoned for multiple units and where the lot size is large enough to meet the zoning requirement for multiple households.

Determining how much is actually zoned for single-family residences is actually a bit more nuanced than just the high-level zoning designation. For example, R-2 zoning allows two units per parcel (e.g. duplexes), but if you're on a 5,900 square foot R-2 lot, you're still actually zoned for a single-family residence because your lot isn't big enough (per our "intensity standards") for a two-dwelling household. Bozeman's zoning-based lot size minimums, lot width minimums, coverage area maximums, and off-street parking requirements all have tangible ramifications that significantly limit feasible density below "zoned" density.

Accounting for zoning designations and zoning lot size requirements, 51% of Bozeman's residential land is designated for single-family residences only.

Why does this matter? Areas zoned for single-family residences exclude the possibility of building more affordable types of housing (and keeps out lower income individuals who cannot afford a freestanding house). Since existing single-family areas are already developed to their maximum allowed density, 100% of Bozeman's population growth must be absorbed by the remaining 49% of residential areas (or agricultural land not yet part of the city).