Zoning fundamentalsExplainer
Corner, through & reversed corner lots
Setback rules assume a lot has one front, one rear and two sides. Lots on more than one street break that assumption, and the zoning code patches it with a rule for each shape.
Chicago’s definitions
frontrearmost distant, most parallel line
every other property line is a side
Definitions and rules below are Chicago’s, from Title 17, linked to our hosted zoning code. Other cities draw these lines differently; the “Elsewhere” note compares a few. Drawings show small sample blocks, not to exact scale.
Property lines
Front, rear and side lines
Every setback is measured from a property line, so the first job on any lot is naming its lines.
- Front property line: the line along the street. On a lot with more than one street frontage, Chicago lets the owner choose which street line is the front §17-17-0260.
- Rear property line: the line most distant from, and most parallel to, the front §17-17-02139.
- Side property lines: everything else §17-17-02156.
An interior lot, with one street, is the simple case: front on the street, rear on the alley, sides against neighbors. The other three types are below. See setbacks for how each setback is sized.
Overview
The four lot types at a glance
| Lot type | Street frontage | Front line | Rear setback | Extra rule |
|---|---|---|---|---|
| Interior | One street | The street | Opposite the front | — |
| Corner | Two intersecting streets | Owner’s choice | Opposite the chosen front | Street-side setback rules |
| Reversed corner | Two, lots behind face the side street | Owner’s choice | Opposite the front | Side setback ≥ 50% of rear lot’s front yard |
| Through | Two parallel streets | Both | None | Mid-lot or perimeter open space |
How each lot type assigns its lines, and the extra Chicago rule it carries.
Corner lots
Corner lots
The corner lot fronts on street A, so its rear setback sits at the far end and the long edge on street B is a side. Had the owner chosen street B as the front, the rear setback would run along the lot’s other long edge instead.
- The lot described
- Required setback
- Neighboring building
The 135° test matters: under it, a lot on a gentle curve or a shallow bend is not a corner lot, however much street it touches. On a true corner lot, the choice of front decides where the rear setback lands, and with it where the building sits.
- Street-side setbacks. In RT and RM districts no side setback is required on the side abutting a street or alley; the opposite side must then be at least 10% of lot width §17-2-0309-A.
- Townhouses. The street-side setback may drop to 5 ft, and to 3 ft where that matches the neighbors §17-2-0500-G.
- Business and commercial height. Where the height limit depends on frontage, a lot with several frontages uses the shortest §17-3-0408-A. See building height.
- Rooftop enclosures. On a corner lot a stair or elevator enclosure must also be set back from the street-facing side wall §17-17-0311-C.
Reversed corner lots
Reversed corner lots
Picture the end of a block where the houses turn to face the side street. The corner lot’s street side lines up with their fronts, so a house built to the corner would stick out in front of the whole row. The rule prevents that:
The three lots behind the corner lot face street B with 20 ft front yards (dashed line). The corner lot’s setback along street B must be at least half that: 10 ft (blue line).
- The lot described
- Required setback
- Neighboring building
One more condition: no accessory building on a reversed corner lot may sit within 5 ft of a rear lot line that abuts the side line of an RS-1, RS-2 or RS-3 lot §17-2-0309-B. In B and C districts the rule applies only when the lot to the rear is residentially zoned §17-3-0406-A.
This is one of the easiest rules to miss: nothing about the corner lot itself shows it. You have to look at which way the next lot faces. LotGrade’s analyzer asks you to pick that lot on the map and reads its front yard.
Through lots
Through lots
On a through lot both street lines are front property lines and the front setback applies at each; rear setback standards don’t apply §17-2-0309-C. To keep light and air in the middle of deep lots, every floor with dwelling units on a through lot 125 ft or deeper must provide one of:
- Mid-lot open space across the full width: 10 ft, plus 2 ft for every 5 ft (or fraction) of depth beyond 125, up to 60 ft.
- Perimeter open space along every non-street line: 5 ft, plus 1 ft for every 5 ft beyond 125, up to 30 ft.
A 150 ft through lot has a front setback at each street and no rear setback. Its two buildings are separated by 20 ft of mid-lot open space: 10 ft, plus 2 ft for each of the five 5-ft steps beyond 125 ft.
- The lot described
- Required setback
- Neighboring building
| Lot depth | Mid-lot open space | Or perimeter open space |
|---|---|---|
| 125 ft | 10 ft | 5 ft |
| 150 ft | 20 ft | 10 ft |
| 175 ft | 30 ft | 15 ft |
| 200 ft | 40 ft | 20 ft |
| 250 ft | 60 ft | 30 ft |
Open space required by lot depth, from §17-2-0309-C. In RM-5 through RM-6.5 the mid-lot space may start at the same height as the district’s rear setback.
Questions
Common questions
Which side is the front of a corner lot?
In Chicago, on a lot with more than one street frontage the owner may choose either street line as the front property line (§17-17-0260). The rear property line is then the one most distant from and most parallel to that front (§17-17-02139); every other line is a side line.
What is a reversed corner lot?
In Chicago, a corner lot whose street-side line is, in effect, a continuation of the front line of the lot behind it — because the lots behind it face the side street (§17-17-02148). Its side setback on that street must be at least half the front yard of the lot to its rear (§17-2-0309-B), so the corner building cannot run right up to the side street in front of that row.
Does a through lot have a rear setback?
No. Both street lines are front property lines, front setbacks apply on both, and rear setback standards do not apply. Instead, residential floors on a through lot 125 feet or deeper need open space mid-lot or along the side lines (§17-2-0309-C).
Is every lot at an intersection a corner lot?
Not under Chicago’s definition: only if the angle between the two streets is 135 degrees or less (§17-17-0241). A lot on a shallow bend in the road is not a corner lot. New York City, Seattle and Los Angeles’s Downtown code use the same 135-degree test, but not every code does.
Do corner lots get smaller side setbacks?
In RT and RM districts, no side setback is needed on the side that abuts a street or alley, but the other side must then be at least 10% of lot width (§17-2-0309-A). Townhouse developments on corner lots can reduce the street-side setback to 5 feet, or as little as 3 feet to match neighbors (§17-2-0500-G).
Keep reading
Related guides
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Zoning Resources
Floor area ratio (FAR)
How much building a lot can hold, how to calculate it, and why it is often not the limit that binds.
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Zoning Resources
Setbacks & yards
Front, side and rear setbacks: how they are measured, averaged, and what may stick out into them.
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Zoning Resources
Building height
Where height is measured from and to, why flat and pitched roofs differ, and what may rise above the limit.
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Zoning Resources
Density: how many units fit
Minimum lot area per unit, why the answer rounds down, and the exemptions that add a unit.
For a real address
Check the real numbers for a real parcel
Lot type changes the setbacks, and a reversed corner lot depends on a neighbor’s front yard. In LotGrade, flag a Chicago lot as a through or reversed corner lot and the setbacks and buildable envelope update; for a reversed corner lot you pick the lot behind it on the map and its front yard is read for you.
The analyzer requires an account — you’ll be asked to sign in. The Zoning Field Guide, the zoning code and these guides are free and need no login.