Zoning Glossary
26 terms defined for real-estate readers.
Overview
Terms that turn up across every city, state, and overlay page in the corpus. Written for readers who are competent in real estate but not fluent in planner-speak.
Terms
By-right
A use or project that is permitted under the base zoning without discretionary approval — planning staff verify compliance and the permit issues.
Opposite of 'discretionary'. When a state law makes something 'by-right', the city cannot require a public hearing or design review to approve it.
Ministerial
An approval that a city staffer issues by checking boxes against objective standards. No public hearing, no discretion.
Core concept in CA SB 35, SB 423, AB 2011 and similar streamlining laws. Ministerial is a stricter standard than by-right — the objective standards are the whole interface.
Discretionary
An approval that requires a decision-maker to exercise judgment — typically via planning commission or city council hearing.
Rezonings, special use permits, variances, and most design reviews are discretionary. Preemption laws typically target discretionary approvals for elimination.
Preemption
State or federal law that overrides what a city would otherwise decide on its own.
US zoning is generally a city power. Preemption laws carve out specific topics — ADUs, density near transit, prefab housing — where the state takes back authority.
Overlay (zone)
A layer of additional or alternative rules that applies on top of the base zoning within a defined geographic boundary.
Example: a historic district overlay, a transit-oriented development overlay, a floodplain overlay. In OnlyPlans' schema, overlays are modeled as trigger predicates + preempted-fields tuples.
Base district
The primary zoning classification assigned to a parcel — e.g. R-1, C-2, MU-5. Determines default use, bulk, height, parking, etc.
Every parcel has exactly one base district. Overlays stack on top of it. The evaluator resolves the effective ruleset by applying overlays in priority order onto the base.
See also:The 5-layer data model
FAR (Floor-Area Ratio)
Total built floor area divided by lot area. FAR 2.0 on a 10,000 sf lot allows 20,000 sf of building.
Often the binding constraint on downtown sites. Height and setback also bind, but FAR is the single number most tightly correlated with yield.
Setback
Minimum distance between a structure and a property line.
Front, side, and rear setbacks usually differ. Setbacks plus height envelope plus parking requirements together define the buildable volume.
Lot coverage
Percentage of the lot that can be covered by buildings (footprint).
Distinct from FAR — lot coverage governs the ground footprint; FAR governs total floor area across stories.
Home rule
A governance model where cities adopt their own zoning and building codes independently of the state.
Texas, Colorado, and Illinois are classic home-rule states. The state may set a minimum building-code edition, but cities can and do adopt newer editions.
See also:Texas — canonical home-rule example
Statewide mandatory (minimum)
A governance model where the state adopts a single edition/code that all cities must follow.
California, Florida, and New York are statewide-mandatory for building codes. Cities can adopt more restrictive amendments, but cannot be less restrictive.
ADU
Accessory Dwelling Unit — a second, smaller residence on a lot with a primary dwelling.
Also called a granny flat, casita, or in-law unit. Many states have preempted city ADU bans: CA AB 68, OR HB 2001, AZ HB 2297.
JADU
Junior ADU — an ADU ≤ 500 sf within an existing dwelling, typically a converted garage or bedroom with its own entry.
California-specific. JADUs trigger fewer impact fees than full ADUs.
See also:CA ADU/JADU statute
Builder's remedy
A California mechanism (Gov Code §65589.5) that lets developers bypass a city's zoning if the city lacks a compliant Housing Element.
Rarely invoked historically, but 2022–2024 enforcement has made it a real pressure valve in Southern California.
See also:CA Builder's Remedy detail page
Ministerial ≠ by-right
Subtle but important: by-right means 'no discretion by default'; ministerial means 'no discretion at all, even via design review'.
A city can make something by-right but still require objective design standards. Ministerial strips that second layer too.
Trigger predicate
The boolean expression that determines when an overlay or preemption applies to a given parcel.
In OnlyPlans' overlay-v3 schema: a tree of and/or/not/eq/gte nodes over parcel and city attributes. The evaluator resolves this per parcel.
See also:Evaluator methodology
IBC
International Building Code — the model construction code from the International Code Council. Sets structural, fire, and occupancy rules for commercial and multifamily buildings.
Published on a 3-year cycle: 2015, 2018, 2021, 2024.
See also:IBC adoption by state
IRC
International Residential Code — the ICC's model code for 1–2 family dwellings and townhouses up to 3 stories.
Anything larger falls under the IBC.
See also:IRC adoption by state
IECC
International Energy Conservation Code — the ICC's model code for building envelope and HVAC efficiency.
Has separate Residential and Commercial halves. The 2021 edition was a step-change in envelope stringency; many states still sit on 2015 or 2018.
See also:IECC adoption by state
FAA Part 77
The federal airspace-protection rule that caps structure heights near airports.
Triggers a Form 7460-1 filing for tall structures.
See also:FAA Part 77 detail page
NFIP / SFHA
National Flood Insurance Program / Special Flood Hazard Area. FEMA-designated 100-year floodplain where participation requires minimum elevation and floodproofing rules.
See also:FEMA NFIP detail page
Title 24 (California)
California's omnibus construction code, published by the Building Standards Commission on a 3-year cycle.
Parts: Part 2 = CBC (Building), Part 2.5 = CRC (Residential), Part 6 = CA Energy Code, Part 11 = CALGreen. Note: CA uses UMC/UPC for mechanical/plumbing, not the ICC IMC/IPC.
See also:California code-adoption record
Yield
For a multifamily site: the number of units per acre the zoning permits, before construction constraints.
Yield × avg rent × occupancy = gross potential income. Most upstream number in the pro forma.
Entitlement
The set of regulatory approvals a project needs to proceed to construction — zoning, use, site plan, environmental, building permit.
'Entitlements' is also used as a verb: a project is 'in entitlements' between deal signing and permit issuance.
Missing middle
Housing types between single-family detached and mid-rise apartments — duplexes, triplexes, fourplexes, cottage courts.
Often prohibited by post-war single-family zoning. AZ HB 2720, CA SB 9, and OR HB 2001 all target missing-middle legalization.
Parcel
The legally-defined unit of land — one tax ID, typically one owner.
The atomic unit in OnlyPlans' data model. All preemption predicates and overlay rules resolve at the parcel level.
See also:Parcel in the data model