Information

This map analyzes how much of residential land is dedicated exclusively to single family homes, by-right. The relationship between exclusionary single-family zoning and the housing affordability crisis is explored further in this article by Sabine Brown of Oklahoma Policy Institute, which this map was produced to supplement.

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Methodology and Definitions

Data from INCOG and Tulsa Planning Office and acquired on 11/8/23 .

Zoning Categories: Zoning categories refer to the types of building uses permitted by the city by-right. “By-right” usage refers to a property owner’s use of property and structures consistent with the zoning district’s permissible uses and is therefore not subject to special review and approval. This does not mean that type of building is currently there now.¹ The focus of this analysis is on mapping the administrative burdens hampering our ability to address the housing crisis with future development, not on mapping current active uses.

• Zoning categories are hierarchical.
  
  
  • If the allowable uses include ANY multi-family buildings by-right, the lot is multi-family.
  • If the allowable uses include ANY mixed-use buildings by-right, the lot is mixed-use. Even if it also allows multi-family buildings.
• We determine the building uses allowed by-right by referencing the allowed use table for each zoning designation (R-1, R-2, etc.) in each city’s zoning code. If a zoning overlay, such as Tulsa’s Neighborhood Infill Overlay, permits multi-family or mixed-use in a zoning district where it was disallowed (e.g., RS-3), that overlay determines the zoning category for the zoning lots covered by it.

Residential Land: In our analysis, residential land is land whose primary use is for people to live in. While almost all cities have some land designated as "agricultural" districts, in practice, many of these lots are still used exclusively for residential purposes. Essentially acting as large single-family lots. Land that is not residential is not included in our analysis. Example of non-residential land is land whose building uses are exclusively commercial or industrial.

Multi-family Building: A building designed for occupancy by more than one family. Examples are duplexes, townhouses, multi-unit houses, apartments, and condos.

Mixed-Use: The incorporation of more than one principal land use type within a single structure, vertical mixed-use. For example, a building with retail uses on the ground floor, and offices or residential on the upper floors. Or, it can be different uses planned together on a single site, horizontal mixed use.

• In all cities here, mixed-use districts permit multi-family homes by-right or implicitly through mixed-use buildings (a 5-floor apartment on top of a commercial shop).

Planned Unit Development (PUD): Most generally, a planned unit development (PUD) is a zoning tool that redefines the land uses allowed within a zoning lot/parcel. For example, some PUDs permit building multi-family homes (with some additional restrictions) in single-family zoning districts, or could be as simple as allowing a single-family home development with a smaller or unusual lot size.

• PUDs are excluded from our calculation of the land devoted to single-family homes by-right because they required a discretionary approval process and also because their allowable uses cannot be determined with our data.²
• The precise definition and process for PUD approval varies by municipality. Typically, a planning commission hosts public hearings and recommends approval/disapproval to the city council who have final say.

Manufactured (Mobile) Home: A manufactured home is a factory-built home that is transportable in one or more sections and built according to the national HUD Code.
Mobile homes are factory-built homes built prior to the establishment of the 1976 HUD code. However, people often use these terms interchangeably.

• Manufactured home zoning districts are categorized as single-family when the homes are given large individual lots (lot size is usually similar to a single-family home), and as their own category when on mobile home parks (which usually have density closer to multi-family districts).
• If the zoning district allows for both individual manufactured home lots and mobile home parks, then the district is not classified as “single-family.”

Footnotes:
1: A lot zoned to permit multi-family homes may have a single-family home developed on it, as both are permitted by-right. It is also possible for it to have a commercial use or public use (such as a hospital), usually after a special exemption from the city. Other possibilities include a building use allowed as a legacy use because it was developed before changes in the zoning code, or a zoning code violation caused by the property owner willfully or unknowingly violating the zoning code. Finally, while all data sources come from city departments or official partners, the map is not a substitute for contacting city planning departments to confirm a lot’s current zoning designation.

2: Technically, once a PUD permits a multi-family home in a former single-family district, a multi-family home is allowed by-right unless it is rezoned again. However, usually the more the PUD diverges from the base zoning district, the more onerous the restrictions on what can be built there. So, future developers may have to resubmit a PUD application as conditions change even if they plan to build the same building type. Also, in our zoning data for Oklahoma City and Norman, PUDs replace the base zoning code (R-1 → PUD), so we are unable to determine its current or prior permitted uses without additional data. Since Tulsa’s PUDs overlay the base zoning district, we categorize lots according to the base zoning district and include those lots in our calculation.