Chicago zoning comparison · stepping up to true multifamily
RT-4 vs RM-4.5: which lets you build more?
RM-4.5 carries the larger envelope — FAR 1.7 vs 1.2; on a standard 25 × 125 ft Chicago lot, RM-4.5 permits 4 units by right against 3; the height limits are 47 ft vs 38 ft. They also come from different district families, so the use mix differs: RT-4 allows two-flats, townhouses and multi-unit residential; RM-4.5 allows multi-unit residential and townhouses.
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
| RT-4 Residential Two-Flat, Townhouse 4 | RM-4.5 Residential Multi-Unit 4.5 | |
|---|---|---|
| Max FAR | 1.2 | 1.7 |
| Max height | 38 ft | 47 ft |
| Lot area per unit | 1,000 sf | 700 sf |
| Units on a standard 25×125 ft lot | 3 | 4 |
| Min lot area | 1,650 sf | 1,650 sf |
| Residential parking / unit | 1 | 1 |
| Max lot coverage | 55% | 60% |
| Permitted uses | two-flats, townhouses and multi-unit residential | multi-unit residential and townhouses |
| 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.