Chicago zoning comparison · the most common Chicago upzoning request
RS-3 vs RT-4: which lets you build more?
RT-4 carries the larger envelope — FAR 1.2 vs 0.9; on a standard 25 × 125 ft Chicago lot, RT-4 permits 3 units by right against 1; the height limits are 38 ft vs 30 ft. They also come from different district families, so the use mix differs: RS-3 allows detached single-family homes and two-flats; RT-4 allows two-flats, townhouses and multi-unit residential.
Figures originally read from a Title 17 excerpt in a third-party zoning report dated 18 September 2024. On 24 August 2026 the bulk standards — floor area ratio, lot area per unit, building height and minimum lot area — were re-checked against the current adopted edition 2026-S-73 and found unchanged. Setbacks and parking ratios were not part of that pass and still rest on the 2024 reading. Data snapshot generated 2026-08-24. How this data is produced and checked →
Side by side
| RS-3 Residential Single-Unit (Detached) 3 | RT-4 Residential Two-Flat, Townhouse 4 | |
|---|---|---|
| Max FAR | 0.9 | 1.2 |
| Max height | 30 ft | 38 ft |
| Lot area per unit | 2,500 sf | 1,000 sf |
| Units on a standard 25×125 ft lot | 1 | 3 |
| Min lot area | 2,500 sf | 1,650 sf |
| Residential parking / unit | 2 | 1 |
| Max lot coverage | 45% | 55% |
| Permitted uses | detached single-family homes and two-flats | two-flats, townhouses and multi-unit residential |
| Connected Communities bulk bonus tier | No | No |
Green marks the more permissive value. Setbacks are contextual in both districts and omitted here — see the district pages for the working scalars and the governing formulas.