Glossary

43,560 square feet — about the size of an American football field without the end zones.

See alsosq ftsq ftSquare feet. An acre is 43,560 sq ft; a typical suburban lot is 7,000–10,000.

A unit of earth volume used in grading limits — roughly one dump-truck scoop.

See alsoGrading (cut & fill)Grading (cut & fill)Reshaping land by removing earth (cut) or adding it (fill), often capped by volume.

Dwelling units per acre — the number of homes allowed on each acre of land.

A cap of 16 du/acre means an acre may hold at most sixteen dwellings, however they are arranged: sixteen small houses, one sixteen-unit building, or anything between. It is a limit on count, not on building shape — height, setbacks and lot coverage do that separately, and in practice they often bind first. On a two-acre parcel the same cap permits 32 units.

See alsoDwelling unitDwelling unitOne independent home: its own kitchen, bathroom and entrance.Lot area per dwelling unitLot area per dwelling unitLand required for each home — the same limit as du/acre, expressed per unit instead of per acre.Floor area ratio (FAR)Floor area ratio (FAR)Total floor area divided by lot area — an FAR of 2.0 permits 20,000 sq ft of floor on a 10,000 sq ft lot.

Horizontal-to-vertical: a 2:1 slope falls one foot for every two it runs. Lower numbers are steeper.

See alsoGrading (cut & fill)Grading (cut & fill)Reshaping land by removing earth (cut) or adding it (fill), often capped by volume.Steep slopeSteep slopeGround above a stated gradient, where building is restricted or barred.

Square feet. An acre is 43,560 sq ft; a typical suburban lot is 7,000–10,000.

See alsoacreacre43,560 square feet — about the size of an American football field without the end zones.

The length of a lot line that touches a public street.

Distinct from lot width: a flag lot may be wide at the building but have only a narrow strip of frontage reaching the road. Minimum frontage rules are what make flag lots need special permission in many codes.

See alsoLot widthLot widthHow wide a lot must be, usually measured at the front setback line.

The share of a lot covered by anything water cannot soak through — roofs, drives, patios.

A stormwater control rather than a building-bulk one, which is why a lot can satisfy its lot-coverage limit and still fail this.

See alsoLot coverageLot coverageThe share of a lot that buildings may cover, as a percentage.

The share of a lot that buildings may cover, as a percentage.

See alsoImpervious coverageImpervious coverageThe share of a lot covered by anything water cannot soak through — roofs, drives, patios.Floor area ratio (FAR)Floor area ratio (FAR)Total floor area divided by lot area — an FAR of 2.0 permits 20,000 sq ft of floor on a 10,000 sq ft lot.

How wide a lot must be, usually measured at the front setback line.

See alsoFrontageFrontageThe length of a lot line that touches a public street.

The smallest parcel on which the district allows anything to be built.

The single most consequential number in most residential districts. A one-acre minimum caps the district at roughly one house per acre no matter what the density figure says, and makes smaller existing lots nonconforming.

See alsoacreacre43,560 square feet — about the size of an American football field without the end zones.NonconformingNonconformingLawful when built, but not compliant with the rules now in force; usually allowed to continue but not to expand.Lot area per dwelling unitLot area per dwelling unitLand required for each home — the same limit as du/acre, expressed per unit instead of per acre.

Land a development must leave unbuilt, sometimes required to be usable or planted.

The distance a building must be held back from a lot line.

Measured separately from the front, rear and side lines, and often again from a second street on a corner lot ("street side"). Setbacks fix the building envelope: together with height and lot coverage they determine what can physically fit, frequently more than the density cap does.

See alsoBuild-to lineBuild-to lineA line a building must meet rather than stay behind — the inverse of a setback.Lot coverageLot coverageThe share of a lot that buildings may cover, as a percentage.YardYardThe open space left between a building and its lot line — the space a setback creates.

The open space left between a building and its lot line — the space a setback creates.

See alsoSetbackSetbackThe distance a building must be held back from a lot line.

A line a building must meet rather than stay behind — the inverse of a setback.

Used in form-based and main-street districts to hold a continuous street wall, preventing buildings from being pushed back behind parking.

See alsoSetbackSetbackThe distance a building must be held back from a lot line.Form-based codeForm-based codeZoning that regulates a building’s shape and street relationship rather than the activity inside it.

Total floor area divided by lot area — an FAR of 2.0 permits 20,000 sq ft of floor on a 10,000 sq ft lot.

FAR limits bulk without dictating shape: that same 2.0 could be a two-storey building covering the whole lot, or a four-storey one covering half. It is the usual bulk control in downtown districts, where height and setbacks alone leave too much latitude.

See alsoLot coverageLot coverageThe share of a lot that buildings may cover, as a percentage.Maximum heightMaximum heightThe tallest a building may be, given in feet, in storeys, or both — whichever binds first.du/acredu/acreDwelling units per acre — the number of homes allowed on each acre of land.

Zoning that regulates a building’s shape and street relationship rather than the activity inside it.

See alsoBuild-to lineBuild-to lineA line a building must meet rather than stay behind — the inverse of a setback.Ground-floor transparencyGround-floor transparencyThe share of a ground-floor street wall that must be windows rather than blank surface.

The share of a ground-floor street wall that must be windows rather than blank surface.

See alsoForm-based codeForm-based codeZoning that regulates a building’s shape and street relationship rather than the activity inside it.

The reference point height is counted from — natural grade, finished grade, or the street.

Not a technicality on sloping ground: measuring from finished rather than natural grade can add a full storey, which is why hillside codes usually specify natural grade.

See alsoMaximum heightMaximum heightThe tallest a building may be, given in feet, in storeys, or both — whichever binds first.Steep slopeSteep slopeGround above a stated gradient, where building is restricted or barred.

The tallest a building may be, given in feet, in storeys, or both — whichever binds first.

Feet and storeys are not interchangeable. A 35-foot limit permits three storeys of ordinary residential construction but only two with tall ground-floor retail, so codes that state both are stricter than either alone.

See alsoHeight measured fromHeight measured fromThe reference point height is counted from — natural grade, finished grade, or the street.StoreysStoreysHabitable floor levels. Whether a basement or attic counts is defined by the local code.Step-backStep-backA requirement that upper floors be set further back than the floors below.

The smallest dwelling the district permits, in square feet of living space.

A requirement that upper floors be set further back than the floors below.

Keeps tall buildings from walling in a street, and lets daylight reach the pavement. Distinct from a setback, which applies to the whole building.

See alsoSetbackSetbackThe distance a building must be held back from a lot line.Maximum heightMaximum heightThe tallest a building may be, given in feet, in storeys, or both — whichever binds first.

Habitable floor levels. Whether a basement or attic counts is defined by the local code.

See alsoMaximum heightMaximum heightThe tallest a building may be, given in feet, in storeys, or both — whichever binds first.

Extra units allowed above the base cap in exchange for something — usually affordable homes.

See alsoInclusionary requirementInclusionary requirementA share of new homes that must be sold or let below market rate.

One independent home: its own kitchen, bathroom and entrance.

The unit of account for nearly every density rule. Whether a bedroom suite with a kitchenette counts as a second dwelling unit is exactly what accessory-dwelling rules turn on.

See alsodu/acredu/acreDwelling units per acre — the number of homes allowed on each acre of land.Accessory dwelling unit (ADU)Accessory dwelling unit (ADU)A second, smaller home on a lot that already has one — a garage flat, basement flat or backyard cottage.

A share of new homes that must be sold or let below market rate.

See alsoDensity bonusDensity bonusExtra units allowed above the base cap in exchange for something — usually affordable homes.

Land required for each home — the same limit as du/acre, expressed per unit instead of per acre.

2,000 sq ft per dwelling unit is about 21 units per acre. Codes often state both, and the stricter one governs.

See alsodu/acredu/acreDwelling units per acre — the number of homes allowed on each acre of land.Minimum lot areaMinimum lot areaThe smallest parcel on which the district allows anything to be built.

A secondary activity customarily incidental to the main use of the lot — a garage, a home office.

See alsoAccessory dwelling unit (ADU)Accessory dwelling unit (ADU)A second, smaller home on a lot that already has one — a garage flat, basement flat or backyard cottage.Home occupationHome occupationA business run from a dwelling, permitted so long as it stays subordinate to living there.

Permitted outright: if the plans meet the written rules, permission cannot be withheld.

The strongest form of permission. No hearing, no discretionary vote, no neighbour objection — staff check the drawings against the code and issue the permit. The practical distance between by-right and conditional is measured in months and legal fees, which is why the split matters more than most single numbers in a code.

See alsoConditional useConditional useAllowed only after a discretionary approval — usually a public hearing and a board vote.ProhibitedProhibitedNot allowed in the district at all, short of rezoning or a variance.Not statedNot statedzoneoptics found no statement either way — an absence of data, not a prohibition.

Allowed only after a discretionary approval — usually a public hearing and a board vote.

Also called a special use permit or special exception. The use is contemplated by the district but not guaranteed: the board may impose conditions or refuse. Treat it as "possible", not "permitted".

See alsoBy rightBy rightPermitted outright: if the plans meet the written rules, permission cannot be withheld.VarianceVariancePermission to depart from a specific dimensional rule, granted on a showing of hardship.

Lawful when built, but not compliant with the rules now in force; usually allowed to continue but not to expand.

See alsoMinimum lot areaMinimum lot areaThe smallest parcel on which the district allows anything to be built.VarianceVariancePermission to depart from a specific dimensional rule, granted on a showing of hardship.

zoneoptics found no statement either way — an absence of data, not a prohibition.

Used throughout this site wherever an ordinance does not address a question for a district, or the extraction has not yet reached the section that does. Many codes are also structured so that a use not listed as permitted is impliedly excluded — but that is a local legal question, so we record silence as silence rather than deciding it.

See alsoBy rightBy rightPermitted outright: if the plans meet the written rules, permission cannot be withheld.ProhibitedProhibitedNot allowed in the district at all, short of rezoning or a variance.

A second set of rules laid over the base district, adding requirements without replacing it.

Historic, floodplain and hillside districts are usually overlays. Because an overlay modifies a base district rather than standing alone, this site excludes overlays from district-share statistics rather than counting them as separate regimes.

See alsoHistoric districtHistoric districtAn area where exterior changes need design review to protect its character.FloodplainFloodplainLand expected to flood at a stated frequency, where building carries extra conditions.

Not allowed in the district at all, short of rezoning or a variance.

See alsoVarianceVariancePermission to depart from a specific dimensional rule, granted on a showing of hardship.RezoningRezoningChanging which district applies to a parcel — a legislative act, not an administrative one.

Changing which district applies to a parcel — a legislative act, not an administrative one.

See alsoProhibitedProhibitedNot allowed in the district at all, short of rezoning or a variance.Planned unit development (PUD)Planned unit development (PUD)A negotiated district where a whole site is approved to its own bespoke plan.

Permission to depart from a specific dimensional rule, granted on a showing of hardship.

See alsoConditional useConditional useAllowed only after a discretionary approval — usually a public hearing and a board vote.NonconformingNonconformingLawful when built, but not compliant with the rules now in force; usually allowed to continue but not to expand.

A second, smaller home on a lot that already has one — a garage flat, basement flat or backyard cottage.

Codes commonly attach conditions no other dwelling faces: an owner-occupancy requirement, a floor-area cap tied to the main house, a separate parking space, or a limit of one per lot.

See alsoDwelling unitDwelling unitOne independent home: its own kitchen, bathroom and entrance.Accessory useAccessory useA secondary activity customarily incidental to the main use of the lot — a garage, a home office.

A dwelling built in a factory to a federal standard and transported to the site.

A building of four or more dwelling units. Where zoning is most restrictive.

See alsodu/acredu/acreDwelling units per acre — the number of homes allowed on each acre of land.

One dwelling unit on its own lot, usually detached from its neighbours.

See alsoDwelling unitDwelling unitOne independent home: its own kitchen, bathroom and entrance.TownhouseTownhouseA single-family home sharing side walls with its neighbours, each on its own lot.

Three dwelling units in one building — a triplex.

A single-family home sharing side walls with its neighbours, each on its own lot.

See alsoSingle-family dwellingSingle-family dwellingOne dwelling unit on its own lot, usually detached from its neighbours.

Two dwelling units in one building — a duplex.

Raising crops or livestock, generally including the structures that serve them.

See alsoSilviculture / plant nurserySilviculture / plant nurseryGrowing trees or plants as a crop — forestry and commercial plant production.

An owner-occupied dwelling letting a limited number of guest rooms.

See alsoShort-term rentalShort-term rentalA dwelling let to guests for brief stays — the zoning category behind Airbnb rules.

Supervised care for children or adults during part of the day.

Almost always tiered by the number of people served and whether it operates from a home or a purpose-built facility — hence labels like "day care 2, family". A family day care in a dwelling is often by right where a day care centre is conditional. The thresholds are local.

See alsoHome occupationHome occupationA business run from a dwelling, permitted so long as it stays subordinate to living there.Group homeGroup homeA dwelling shared by unrelated residents receiving supervision or care.

A dwelling shared by unrelated residents receiving supervision or care.

Ordinances routinely split this into numbered tiers — "group home 1", "group home 2" — by resident count, staffing or the population served, and each tier can carry a different permission. Federal fair-housing law also constrains how far a locality may restrict homes for people with disabilities. Read the local definitions section for the operative meaning.

See alsoJuvenile residenceJuvenile residenceA residential facility housing minors under supervision, outside a family household.ShelterShelterTemporary accommodation for people without housing, usually with support services.Nursing homeNursing homeA residential facility providing continuous medical and personal care.

A business run from a dwelling, permitted so long as it stays subordinate to living there.

Typically limited by floor area, employees, signage, customer visits and outward appearance.

See alsoAccessory useAccessory useA secondary activity customarily incidental to the main use of the lot — a garage, a home office.

A residential facility housing minors under supervision, outside a family household.

See alsoGroup homeGroup homeA dwelling shared by unrelated residents receiving supervision or care.ShelterShelterTemporary accommodation for people without housing, usually with support services.

Boarding or breeding animals above the number kept as household pets.

A residential facility providing continuous medical and personal care.

See alsoGroup homeGroup homeA dwelling shared by unrelated residents receiving supervision or care.

A negotiated district where a whole site is approved to its own bespoke plan.

Trades the certainty of by-right rules for flexibility: the developer proposes a mix and layout, the locality approves it as a package, and the approved plan becomes the rule for that land.

See alsoRezoningRezoningChanging which district applies to a parcel — a legislative act, not an administrative one.By rightBy rightPermitted outright: if the plans meet the written rules, permission cannot be withheld.

Infrastructure serving the wider area — substations, pump stations, towers.

A building used for organised worship, often with halls and schools attached.

In the United States the Religious Land Use and Institutionalized Persons Act limits how far zoning may burden religious assembly, so these uses are treated more permissively than their traffic and scale alone would suggest.

Temporary accommodation for people without housing, usually with support services.

Distinguished in most codes from a group home by length of stay and from a hotel by the absence of payment. Frequently conditional rather than by right.

See alsoGroup homeGroup homeA dwelling shared by unrelated residents receiving supervision or care.

A dwelling let to guests for brief stays — the zoning category behind Airbnb rules.

The defining threshold is length of stay, commonly under 30 days. Codes differ sharply on whether the host must live there, and on whether a whole-house let is the same use as renting a spare room.

See alsoBed and breakfastBed and breakfastAn owner-occupied dwelling letting a limited number of guest rooms.

Growing trees or plants as a crop — forestry and commercial plant production.

Grouped with agriculture in most codes, and often protected from local regulation by state right-to-farm law. A retail garden centre is usually a separate, commercial use.

See alsoAgricultureAgricultureRaising crops or livestock, generally including the structures that serve them.

A private ramp on a residential lot, regulated as an accessory structure.

Appears as a named use because of noise and height: codes that list it usually cap its size and set it back from lot lines. A public skate park is a separate recreational use.

See alsoAccessory useAccessory useA secondary activity customarily incidental to the main use of the lot — a garage, a home office.

The number of off-street spaces a development must provide before it may open.

Usually set per dwelling unit or per 1,000 sq ft of floor area. Because parking consumes land, a minimum can bind harder than the density cap: a requirement of two spaces per unit can make the permitted number of units physically impossible to fit. Most codes set these in a citywide chapter rather than per district.

See alsodu/acredu/acreDwelling units per acre — the number of homes allowed on each acre of land.Lot coverageLot coverageThe share of a lot that buildings may cover, as a percentage.

Land expected to flood at a stated frequency, where building carries extra conditions.

See alsoOverlay districtOverlay districtA second set of rules laid over the base district, adding requirements without replacing it.

Reshaping land by removing earth (cut) or adding it (fill), often capped by volume.

See alsocubic yard (cy)cubic yard (cy)A unit of earth volume used in grading limits — roughly one dump-truck scoop.H:V ratioH:V ratioHorizontal-to-vertical: a 2:1 slope falls one foot for every two it runs. Lower numbers are steeper.

An area where exterior changes need design review to protect its character.

See alsoOverlay districtOverlay districtA second set of rules laid over the base district, adding requirements without replacing it.

A strip along a stream or wetland that must be left undisturbed.

A formula that reduces permitted density as the ground gets steeper.

Common in hillside codes: the steeper the average natural slope, the fewer units the same acreage will carry — so the nominal du/acre figure overstates what a sloping site can actually hold.

See alsodu/acredu/acreDwelling units per acre — the number of homes allowed on each acre of land.Steep slopeSteep slopeGround above a stated gradient, where building is restricted or barred.

Ground above a stated gradient, where building is restricted or barred.

See alsoSlope densitySlope densityA formula that reduces permitted density as the ground gets steeper.Grading (cut & fill)Grading (cut & fill)Reshaping land by removing earth (cut) or adding it (fill), often capped by volume.H:V ratioH:V ratioHorizontal-to-vertical: a 2:1 slope falls one foot for every two it runs. Lower numbers are steeper.

The long-range policy document zoning is meant to implement; it is not itself binding law.

The doctrine that a local government has only the powers the state expressly grants it.

See alsoHome ruleHome ruleA grant of broad self-government, letting localities act without specific state authorisation.Enabling statuteEnabling statuteThe state law granting local governments the power to zone at all.

The state law granting local governments the power to zone at all.

No locality zones on its own authority. The terms of the delegation set the outer bounds of any local ordinance, and determine whether counties may zone unincorporated land.

See alsoDillon's RuleDillon's RuleThe doctrine that a local government has only the powers the state expressly grants it.Home ruleHome ruleA grant of broad self-government, letting localities act without specific state authorisation.

A rule binding every district rather than one — sign, parking and floodplain chapters.

Most of an ordinance’s volume by page count. Because these carry no zone code, they are listed separately from districts throughout this site.

See alsoZoning districtZoning districtA mapped area with one set of rules, identified by a code like R-1 or B-2.

A grant of broad self-government, letting localities act without specific state authorisation.

See alsoDillon's RuleDillon's RuleThe doctrine that a local government has only the powers the state expressly grants it.Enabling statuteEnabling statuteThe state law granting local governments the power to zone at all.

A mapped area with one set of rules, identified by a code like R-1 or B-2.

The basic unit of zoning. Every parcel sits in exactly one base district, which fixes what may be built and how large — possibly modified by overlays.

See alsoOverlay districtOverlay districtA second set of rules laid over the base district, adding requirements without replacing it.General provisionGeneral provisionA rule binding every district rather than one — sign, parking and floodplain chapters.