RT-4 Residential Two-Flat, Townhouse and Multi-Unit District A Chicago zoning district · Title 17
Two-flats, townhouses and low-density apartment buildings. RT districts accommodate a mix of housing types at moderate density. The "A" suffix on RT-4A marks accessible-unit standards, not bonus floor area: RT-4A is built to RT-4's own floor area ratio, and the accessible-unit incentive is an exemption — ground floor Type A units are left out of the floor area counted and out of the lot-area-per-unit calculation, so what it is worth depends on the building.
Example on a 25 × 125 ft lot. The dashed box is the maximum zoning envelope, the buildable footprint after setbacks, raised to the 38 ft height limit. The solid building is an illustrative example at FAR 1.2: covering the full footprint reaches only ~3 stories before the floor-area cap binds, so a taller building needs a smaller floor plate. Residential floors sit over a partially above-grade basement, which counts toward height but not floor area. Front yard is context-dependent (average of adjacent lots); actual varies.
Specifications
- Zoning Ordinance reference
- §17-2-0100
View in the Chicago Zoning Ordinance - Floor area ratio (FAR)
- 1.2Ground floor Type A (accessible) units, except in a detached house, are not counted as floor area. That is an exemption, not a higher ratio: it is worth whatever those units occupy, on top of this FAR — §17-2-0304-D
- Maximum building height
- 38 ft, measured to the top floor's ceiling (flat roof) or mean roof height (pitched roof). §17-17-0311.
- Lot area per unit (density)
- 1,000 sq ft of lot area per dwelling unit. 1,000 sq ft per efficiency unit; 500 sq ft per SRO unit.Ground floor Type A (accessible) units, except in a detached house, are left out of this calculation, so each one is a unit above what the lot area alone allows — §17-2-0303-B(2)
- Minimum lot area
- 1,650 sq ft
- Rear yard open space
- The greater of 65 sq ft per unit or 6.5% of lot area, containing a circle at least 12 ft in diameter. Must sit in the rear yard, at or within 4 ft of grade. §17-2-0307.
- On-site open space
- —
- Parking requirements
- 1 space per dwelling unit. §17-10-0207.
Setbacks
- Front yard
- The lesser of 15 ft or 12% of lot depth, or the average of the adjacent lots. §17-2-0305.
- Side yard
- Combined at least 20% of lot width; each side at least 2 ft or 8% of width (no side required to exceed 5 ft). §17-2-0309.
- Rear yard
- The lesser of 50 ft or 30% of lot depth; 28% for a detached house; 24% for a building of no more than 19 units in which at least 33% of the units are accessible. §17-2-0306.
Allowed Uses
Curated from the §17-2-0207 use table. P = permitted by-right; S = special-use approval required. Always confirm against the full ordinance text.
- Detached house
- Two-flat
- Townhouse
- Multi-unit (3+) residential
- Elderly housing
- Single-room occupancy (RT4)
- Conversion unit & coach house
- Day care; schools; religious assembly
- Parks & recreation; community gardens
- Cultural exhibits & libraries; hospital (RT4)
- Bed & breakfast (RT4); vacation rental
- Community home (group)
- Domestic violence residence / shelter (RT4)
- Nursing home / group living (RT4)
- Temporary overnight shelter; transitional shelters
- Lodge or private club (RT4)
- Community / recreation centers; police station
- Major utilities; non-accessory parking
- Freestanding wireless towers
In Chicago, RT-4 allows a floor area ratio of 1.2 and a minimum lot area of 1,650 sq ft, with a height limit of 38 ft. The figures above are the RT-4 standards as the Chicago Zoning Ordinance states them, each citation linking to the section it comes from in our hosted copy of Title 17. What a specific lot allows also depends on its frontage, depth, corner or through geometry, and any overlay it sits in — run the RT-4 numbers for your lot to see those applied.
Reference figures are modeled from the Chicago Zoning Ordinance (Title 17) for general guidance and do not constitute zoning or legal advice. Lot-specific limits depend on frontage, depth, adjacencies and overlays — analyze a specific address for exact figures. Always confirm against the official ordinance.