RM-5.5 Residential Multi-Unit District
Medium- to high-density apartment buildings. RM districts carry the city's highest residential floor-area ratios; RM-6 and RM-6.5 require Planned Development review for tall buildings.
Example on a 100 × 125 ft lot. The dashed box is the maximum zoning envelope, the buildable footprint after setbacks, raised to the 60 ft height limit. The solid building is an illustrative example at FAR 2.5: covering the full footprint reaches only ~4 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)
- 2.5
- Maximum building height
- 47 ft; 60 ft where the zoning lot has at least 100 ft of frontage. §17-2-0305.
- Lot area per unit (density)
- 400 sq ft of lot area per dwelling unit. 400 sq ft per efficiency unit; 200 sq ft per SRO unit.
- Minimum lot area
- 1,650 sq ft
- Rear yard open space
- —
- On-site open space
- 36 sq ft of usable on-site open space per dwelling unit (min. dimension 5 ft if private, 15 ft if common). Outdoor only — not parking, loading, or mechanical areas. §17-2-0308.
- 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 24% of lot depth (under 20 units); 30% of depth for 20 or more units. §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
- Assisted living
- Conversion unit & coach house
- Day care; schools; religious assembly
- Parks & recreation; community gardens
- Colleges & universities; hospital
- Bed & breakfast; vacation rental
- Residential support service (RM6-6.5)
- Domestic violence shelter; nursing home
- Group living not otherwise classified
- Temporary overnight shelter; transitional shelters
- Lodge or private club
- Government health center
- Community / recreation centers; police station
- Major utilities; non-accessory parking
- Freestanding wireless towers
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.