Zoning fundamentalsExplainer
Building height, explained
A height limit sounds simple until you ask where to measure from and to. The answer depends on the roof, on the ground around the building, and on a short list of things allowed to rise above the line.
How Chicago measures it
heightgradetop floor’s ceiling
pitched roof: grade → midpoint of eave and ridge
The measurement rules below are Chicago’s, from Title 17, linked to our hosted zoning code. Other cities measure from and to different points; the “Elsewhere” note compares a few. Drawings are at true vertical scale.
Definition
What “building height” means
Building height is a vertical distance from a fixed starting point, grade, to a fixed point on the building. Zoning codes differ mostly on the second point: the top of the roof, the top of the parapet, the ceiling of the top floor, or somewhere on a sloped roof.
Where the measurement starts: grade
Chicago defines grade as the curb level next to the front property line or the mean finished grade along the building’s exterior walls, whichever is higher §17-17-0265. On a lot that sits below the street, height is still measured from the curb.
Stories and floors
A story is the space between one floor and the next §17-17-02169. A basement counts as a story only when more than half of its floor-to-ceiling height is above grade. For the height rule, a “floor” is any enclosed area with at least 6 ft 9 in of headroom §17-17-0311-A.
Measurement
Flat roofs, pitched roofs, and what sticks up
Chicago measures to the underside of the top floor’s ceiling joists on a flat roof, and to the mean height between eaves and ridge on a gable, hip, mansard or gambrel roof §17-17-0311-A. That is a Chicago choice, not a national standard.
Flat roof
To the top ceiling
Three floors of 12 ft put the top ceiling at 35 ft. The roof deck and parapet above it (gray) are not part of the measured height.
Pitched roof
To the midpoint
Eaves at 26 ft and a ridge at 38 ft measure 32 ft, so a ridge can rise well above a 30 ft limit.
Rooftop
Allowed above the limit
A stair enclosure to a roof deck may exceed the limit if it is set back 20 ft from the front wall and stays within size limits.
What may rise above the height limit
- Stair and elevator enclosures serving an occupiable roof, and elevator penthouses §17-17-0311-C. In R districts: set back 20 ft from the front building line, and a stair-only enclosure up to 200 sq ft and 13 ft tall; with an elevator, up to 500 sq ft and 19 ft 6 in. These enclosures also don’t count as floor area for FAR.
- Solar panels on a flat roof, up to 9 ft tall or 5 ft above the parapet, whichever is lower §17-17-0311-B.
- Pergolas and trellises on a roof deck, set back 20 ft from the front on buildings under 80 ft, up to 11 ft above the deck or 8 ft above the parapet, whichever is greater.
- Rooftop wind turbines, set back 20 ft and up to 15 ft above the roof or parapet.
On a corner lot, a rooftop enclosure must also be set back from the street-facing side wall by half the distance between the side building lines §17-17-0311-C.
Chicago
Height limits in Chicago
Residential districts set a single limit for residential buildings, with a few adjustments for lot width and accessible units §17-2-0311. Principal nonresidential buildings in R districts have no listed height limit.
| District | Height limit | Notes |
|---|---|---|
| RS-1 | 30 ft | |
| RS-2 | 30 ft | |
| RS-3 | 30 ft | |
| RT-3.5 | 35 ft | |
| RT-4 | 38 ft | 42 ft if at least 25% of units are Type A (buildings of 19 units or fewer) |
| RM-4.5 | 45-47 ft | 45 ft with lot frontage under 32 ft, 47 ft at 32 ft or more |
| RM-5 | 45-47 ft | 45 ft with lot frontage under 32 ft, 47 ft at 32 ft or more |
| RM-5.5 | 47-60 ft | 47 ft with lot frontage of 75 ft or less, 60 ft above that |
| RM-6 | No limit (PD review) | No fixed limit; tall buildings need a planned development |
| RM-6.5 | No limit (PD review) | No fixed limit; tall buildings need a planned development |
Residential buildings in R districts. Limits come from the same rule table the LotGrade analyzer uses; each district links to its Field Guide page.
Business and commercial districts
In B and C districts the limit depends on the dash number, the lot frontage, and whether the building has ground-floor commercial space that meets §17-3-0305 §17-3-0408-A. A lot with more than one frontage uses the shortest.
| District | ≤ 25 ft | 25–50 ft | 50–99.9 ft | 100 ft + |
|---|---|---|---|---|
| Dash 1, 1.5 | 38 | 38 | 38 | 38 |
| Dash 2 | 47 / 45 | 50 / 45 | 50 / 45 | 50 / 45 |
| Dash 3 | 50 / 50 | 55 / 50 | 65 / 60 | 65 / 60 |
| Dash 5 | 50 / 50 | 55 / 50 | 70 / 65 | 80 / 75 |
Maximum height in feet, with / without qualifying ground-floor commercial space, by lot frontage. Dash 1 and 1.5 are 38 ft with commercial space; the table lists no figure without it. From §17-3-0408-A.
Going higher
- Administrative adjustment: up to 10% more height §17-13-1003-L; in RS districts, up to 10% in exchange for a deeper rear setback, one foot per two extra feet of setback §17-13-1003-N.
- Transit-served locations: B-3 and C-3 projects near CTA or Metra rail, or on listed bus corridors, can gain height through a Type 1 rezoning or a planned development §17-3-0408-B.
- Planned developments: required above set thresholds — 110 ft in RM-6, 140 ft in RM-6.5, and 75 or 80 ft in dash-5 districts §17-8-0512. See zoning relief in Chicago.
Questions
Common questions
How is building height measured?
It varies by city. In Chicago, from grade to the underside of the top floor’s ceiling joists on a flat-roofed building, or to the midpoint between the eaves and the ridge on a gable, hip, mansard or gambrel roof (§17-17-0311-A). Seattle and Denver measure to the highest point of the structure, Los Angeles to the top of the roof or parapet, and New York City from a “base plane” tied to the curb and grade — so always check the local definition.
What is “grade” when measuring height?
The starting point differs by city. Chicago uses the curb level next to the front property line or the mean finished grade along the building’s exterior walls, whichever is higher (§17-17-0265). Raising the yard therefore raises the starting point; lowering it does not lower it below the curb.
Does a basement count as a story?
Codes differ. In Chicago it does when more than half of its floor-to-ceiling height is above grade (§17-17-02169). A garden unit sunk halfway into the ground usually is not a story; one that is mostly above ground is.
Can a rooftop deck stair or elevator go above the height limit?
Yes, within limits. In residential districts a stair-only enclosure set back at least 20 feet from the front building line may cover up to 200 sq ft and rise 13 feet above the top floor’s ceiling (§17-17-0311-C). Solar panels, pergolas and some wind equipment have their own allowances (§17-17-0311-B).
What is the height limit in Chicago?
30 feet in the RS districts, 35 in RT-3.5 and 38 in RT-4, 45 to 60 in the RM-4.5 through RM-5.5 districts, and no fixed limit in RM-6 and RM-6.5, where tall buildings go through a planned development. In business and commercial districts the limit depends on the dash number, the lot frontage and whether the ground floor has qualifying commercial space (§17-3-0408-A).
Can I get a height increase?
The Zoning Administrator can approve up to 10% more height in some cases (§17-13-1003-L), and in RS districts up to 10% in exchange for a deeper rear setback — one foot of height for every two feet of extra setback (§17-13-1003-N). Transit-served dash-3 sites can go higher through a rezoning or planned development (§17-3-0408-B).
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
Density: how many units fit
Minimum lot area per unit, why the answer rounds down, and the exemptions that add a unit.
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Zoning Resources
Corner, through & reversed corner lots
Which line is the front, where the rear yard goes, and the extra setback a reversed corner lot owes.
For a real address
Check the real numbers for a real parcel
The height limit that applies to a lot can depend on its frontage and the building you plan. LotGrade reads the district and frontage for any Chicago address, applies the right limit, and shows how many floors fit alongside setbacks and FAR.
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