In a letter to the editor of the Seattle Times from November 2015 David Sucher proposed taking literally Seattle City Councilmember Juarez’s straw-man argument that we not allow “triplexes on every block” to alleviate the housing crisis. Calculating the number of blocks in single-family zones and the 31,480 unit increase in the housing supply that would be added by literally adding one triplex on every such block in Seattle, Sucher concludes that this would be an excellent strategy to address the mayor’s Housing and Affordability and Livability Agenda housing creation goal of adding 50,000 units city wide, while having the minimum possible impact on the character and built fabric of the city’s neighborhoods.
The council member and Mr. Sucher’s reasonable suggestion is unlikely to be put in place because it defies the logic of existing zoning laws, which are little changed from the first zoning laws developed by the City of New York and approved by the Supreme Court in the 1920’s. These laws created a defined three-dimensional space in which buildings could be constructed as they also meet the restrictions on land use and occupancy specified in the zoning. These zones usually encompass at least one city block in area though they have been retroactively applied to built environments that predate zoning in order to match the finer grain of those neighborhoods.
This type of regulation has little impact when the maximum allowed envelope is substantially larger than the existing buildings within the zone. However, many zoning codes have been crafted to hold a neighborhood’s form strictly in place, even to the point of creating “nonconforming uses”: existing buildings that would be illegal to build under the new code. Compounding matters, zoning codes are rarely updated to reflect growth in regional population. The result is that in cases of high demand blocks with extra zoning capacity are quickly built to capacity, resulting in the wholesale elimination of the built legacy of the building and what is often a monotonous block of similar buildings designed to maximize zoning limitations and construction efficiencies.
Alternative approaches to zoning have been proposed, the most prominent being “form-based codes” which regulate the types of buildings that can be built rather than merely their maximum physical dimensions.
Mr. Sucher’s approach to regulate building by type based on the existing population of buildings on the block would be a novel approach. Such a quota could distribute new buildings according to the needs of the city across the city, preventing any particular neighborhood from bearing the burden of too quick growth, and ensuring a diverse, gradually evolving built environment.
Alternately the city could regulate building based on the number of units for the block (or acre). If 20 units currently exist on the block, and 30 are allowed, either ten single-family homes could add backyard cottages, be subdivided into or replaced by duplexes, or one house could be replaced by an 11 unit apartment building. An advantage of this approach would be to allow capacity to be increased incrementally and systematically with the rise in population of the city or region. If the city population increased 1%, every neighborhood in the city could be required to increase capacity by 1%. Some neighborhoods would see no change for several years as additional capacity accumulated, others would see piecemeal replacement of aging building stock with slightly more unit-dense buildings. By making zoning capacity increases essentially automatic this approach could temper the fierce resistance that “upzoning” often faces when proposed by planners and elected officials. Residents would generally not see large-scale replacement of the building stock of their neighborhood in a short period of time.
Such a unit quota system of zoning would be a drastic change from our existing system. Still, it is worth reconsidering if our nearly 100 year old system hasn’t gone stale.