Zoning is the city’s rule for what can be built on a lot: what it can be used for, how many homes it can hold, how big the building can be. Every lot in Chicago has one district code, and some lots sit under one or more overlays that change the answer. This page reads the code the way the report does.
A code like RT-4 or B3-2 has up to three parts.
The letters say what kind of place it is: R residential, B business, C commercial, D downtown, M manufacturing.
Inside a family, a higher number allows more. B1 is small storefronts; B3 is shopping centers. RS is one house; RM is apartments.
How much building the lot can carry: floor area, homes per lot, height. Residential codes fold this into the use number.
Two district codes cover most of the city’s houses and flats. RS-3 is the standard single-family lot. RT-4 is the standard two-flat and three-flat lot: one home per 1,000 square feet of lot, so a 25 by 125 foot lot holds three.
| Code | Family | What it is | Homes |
|---|---|---|---|
| RS | Residential single-unit | Detached houses. One home per lot. | Yes |
| RT | Residential two-flat, townhouse and multi-unit | Two-flats, three-flats, townhouses and small walk-ups. | Yes |
| RM | Residential multi-unit | Apartment buildings. The number after the dash sets how dense. | Yes |
| B | Business | Neighborhood shopping streets. Apartments allowed above stores (B2 also at street level). | Above the ground floor |
| C | Commercial | Busier commercial corridors, taverns and auto uses. Apartments above the ground floor except in C3. | Above the ground floor |
| DC | Downtown core | The Loop. Office towers, hotels and residential at the highest densities. | Yes |
| DX | Downtown mixed-use | High-density mixed use around the Loop: River North, West Loop, South Loop. | Yes |
| DR | Downtown residential | High-rise residential near downtown, limited ground-floor commercial. | Yes |
| DS | Downtown service | Downtown-edge service and light industrial. Dwellings only above the ground floor. | Above the ground floor |
| M | Manufacturing | Industrial, warehousing and distribution. No homes. | No |
| PMD | Planned manufacturing district | Protected industrial corridors. Residential conversion is barred by ordinance. | No |
| PD | Planned development | A site-specific ordinance replaces the standard rules. Read the PD document for what is allowed. | Per the PD |
| POS | Parks and open space | Parks, playlots and natural areas. Buildings need the owning agency’s approval. | No |
| T | Transportation | Rail yards, expressways and transit facilities. | No |
Floor area ratio (FAR) is total building floor area divided by lot area. FAR 1.2 on a 3,125 square foot lot allows 3,750 square feet of building across all floors.
Lot area per unitis how much lot each home needs. Divide the lot by it, round down, and that is the most homes the district allows for new construction. Buildings that predate the 1957 ordinance often hold more and remain legal non-conforming; the city’s zoning certificate, not this arithmetic, settles the legal count on a sale.
Height is the cap in feet for the common case. Business and downtown districts vary it by lot width and ground-floor use, so the report shows the top of the range.
| District | Max FAR | Min lot | Lot per home | Height | In short |
|---|---|---|---|---|---|
| RS-1 | 0.5 | 6,250 | 6,250 | 30 ft | Large-lot detached houses. One home per 6,250 square feet of lot. |
| RS-2 | 0.65 | 5,000 | 5,000 | 30 ft | Detached houses on 5,000 square foot lots. |
| RS-3 | 0.9 | 2,500 | 2,500 | 30 ft | Detached houses on standard 25 by 125 foot city lots. The most common single-family zoning in Chicago. |
| RT-3.5 | 1.05 | 2,500 | 1,250 | 35 ft | Two-flats and townhouses at a scale that fits beside single-family blocks. One unit per 1,250 square feet of lot. |
| RT-4 | 1.2 | 1,650 | 1,000 | 38 ft | Two-flats, three-flats, townhouses and small apartment buildings. One unit per 1,000 square feet of lot, so a standard 3,125 square foot lot supports three units. |
| RT-4A | 1.2 | 1,650 | 1,000 | 38 ft | RT-4 with a bonus for buildings under 20 units where at least a third of the units are accessible: FAR 1.5 and 42 feet instead of 1.2 and 38. |
| RM-4.5 | 1.7 | 1,650 | 700 | 47 ft | Low-rise apartment buildings. One unit per 700 square feet of lot. |
| RM-5 | 2 | 1,650 | 400 | 47 ft | Mid-rise apartment buildings. One unit per 400 square feet of lot. |
| RM-5.5 | 2.5 | 1,650 | 400 | 60 ft | Mid-rise apartment buildings with more floor area than RM-5. |
| RM-6 | 4.4 | 1,650 | 300 | No cap | High-rise residential, mostly along the lakefront. One unit per 300 square feet of lot. |
| RM-6.5 | 6.6 | 1,650 | 300 | No cap | The densest residential district outside downtown. |
B1, B2, B3, C1, C2 and C3 all use the same dash table. The use letters say what kind of business; the dash says how much building.
| Dash | Max FAR | Lot per home | Height | Note |
|---|---|---|---|---|
| -1 | 1.2 | 2,500 | 38 ft | Thirty-eight feet. |
| -2 | 2.2 | 1,000 | 50 ft | Forty-five to 50 feet, by lot frontage and ground-floor use. |
| -3 | 3 | 400 | 65 ft | Fifty to 65 feet, by lot frontage and ground-floor use. |
| -5 | 5 | 200 | 80 ft | Fifty to 80 feet, by lot frontage and ground-floor use. |
| -1.5 | 1.5 | 1,350 | 38 ft | Thirty-eight feet. |
C3 allows no dwellings at any dash. In B1, B3, C1 and C2 homes go above the ground floor; B2 allows them at street level too.
| Dash | Base FAR | Lot per home |
|---|---|---|
| -3 | 3 | 400 |
| -5 | 5 | 200 |
| -7 | 7 | 145 |
| -10 | 10 | 115 |
| -12 | 12 | 115 |
| -16 | 16 | 100 |
Downtown has no fixed height cap. Buildings above the planned-development threshold go through PD review, and extra floor area is bought through the Neighborhood Opportunity Fund bonus system.
| Dash | Max FAR |
|---|---|
| -1 | 1.2 |
| -2 | 2.2 |
| -3 | 3 |
An overlay sits on top of the district. The report lists every one the property is inside.
| Overlay | What it does |
|---|---|
| Planned development | A site-specific ordinance governs this land instead of the base district. |
| PMD subarea | A subarea of a planned manufacturing district with its own use list. |
| Pedestrian street | Designated pedestrian retail street: storefront frontage required, curb cuts and drive-throughs restricted, and the transit-served radius doubles. |
| Transit-served location (rail) | Within 2,640 feet of a CTA station entrance. Parking minimums can drop to zero and density bonuses apply. |
| Transit-served location (Metra) | Within 2,640 feet of a Metra station entrance. Same parking and density relief as CTA rail. |
| Transit-served location (bus corridor) | Within 1,320 feet of a high-frequency bus corridor under the 2022 Connected Communities ordinance. |
| ADU opt-in area | Single-family (RS) zoning here has been opened to additional dwelling units by the alderperson, with the listed limits. |
| ADU downtown exclusion | Additional dwelling units are not permitted in the downtown core. |
| Affordable Requirements Ordinance area | Sets the affordable-unit share for new residential projects of ten or more units. Community Preservation areas also bar converting two- and three-flats to single-family near transit. |
| Lakefront protection district | Development within the Lake Michigan and Chicago Lakefront Protection Ordinance zone needs Plan Commission review. |
| Special purpose district | An overlay with its own use or design rules (17-7). |
| FEMA flood zone | FEMA flood insurance rate map zone letter. Zones starting with A or V are special flood hazard areas. |
| Zoning Board of Appeals decision | A recorded variance or special-use decision on this parcel. |
Since the 2022 Connected Communities ordinance, a lot within 2,640 feet of a CTA or Metra station entrance, or 1,320 feet of a high-frequency bus corridor, is transit-served. Parking minimums fall by half and can go to zero, and B3 and C3 districts at dash 3 can earn more floor area and units by including affordable homes.
Since April 1, 2026 a coach house or a basement or attic unit is allowed by right in RT, RM, B and C1/C2 districts outside the downtown core. In RS districts the alderperson opts blocks in, and the opt-in area can carry limits: a yearly cap, an owner-occupancy rule, or case-by-case administrative review. One to four unit buildings may add one unit. Larger buildings may add more, with an affordability rule once two or more are added.
In the Affordable Requirements Ordinance’s community preservation areas near transit, an existing two-flat or three-flat cannot be converted to a single-family house without a downzoning.
Districts and overlays come from the City of Chicago zoning map service, refreshed monthly. Numbers follow the Chicago Zoning Ordinance bulk and density tables (Title 17, chapters 2 through 6). This page is a reference, not zoning advice; the ordinance and the Zoning Administrator control.