Ordinance explainer · Affordable Requirements Ordinance
The ARO inside Chicago's zoning code: where affordability changes what you can build
Chicago's Affordable Requirements Ordinance lives in Municipal Code Chapter 2-44 — outside the zoning title — and that's where its coverage thresholds, set-aside percentages and in-lieu fees are set. But the zoning ordinance is where the ARO changes a project's physical envelope: on-site ARO share is the currency of the Connected Communities bonuses (FAR 3.0 → 4.0, lot area per unit 400 → 300 sq ft, height to 80 ft in transit-served -3 districts), community preservation areas flip what housing types are even allowed near transit, and a parking-for-affordability swap converts deleted parking into affordable floor area 1:1. This page maps those zoning-side hooks, with citations.
Ordinance text quoted from Municipal Code edition 2026-S-73 (current through 2026-02-18). ARO percentages and fees (Title 2) are deliberately not restated here. Data snapshot generated 2026-08-24. How this data is produced and checked →
1 · On-site ARO share buys bulk: the Connected Communities tiers
In the six transit-served -3 business and commercial districts (B1-3 through C3-3), the share of a project's ARO obligation delivered on-site steps up its envelope — minimum one affordable unit, and always through an approval vehicle (Type 1 map amendment, planned development, or ARO-covered entitlement):
| ARO on-site (per §2-44-085) | Max FAR | Lot area / unit | Height effect |
|---|---|---|---|
| 50% | 3.5 | 350 sf | Transit table by frontage, to 75 ft; ≥50% of required affordable units on-site adds +5 ft per band, to 80 ft (§17-3-0408-B) |
| 75% | 3.75 | 325 sf | |
| 100% | 4.0 | 300 sf |
§17-3-0402-B (lot area), §17-3-0403-B (FAR). Downtown D-3 districts carry the same FAR and lot-area tables (§17-4-0404-C, §17-4-0405-C), but floor area gained there can't stack with the §17-4-1000 downtown bonus system. Full mechanics: the Connected Communities guide.
2 · Community preservation areas: the typology guardrails
Where a lot sits inside a community preservation area (defined in §2-44-085(B)) and is transit-served (½ mile rail / ¼ mile designated bus corridor), Title 17 blocks down-building:
- New detached houses are prohibited in RT and RM districts (§17-2-0303-B.3).
- New two-flats are prohibited in RM districts (§17-2-0303-B.4).
- New detached houses and two-flats are prohibited in B and C districts (§17-3-0307.2).
Each rule carries cascading escapes — where the denser typology can't lawfully be established on the lot, the next one down becomes permissible. The intent is one-directional: near transit, in areas the ARO protects, land shouldn't be consumed by the least dense building the district allows.
3 · The parking-for-affordability swap
§17-10-0102-B.4 lets a qualifying transit-served residential project that has (a) hit a mandatory planned-development threshold, (b) maximized its density and FAR standards, and (c) cut its parking beyond 50%, replace the freed parking square footage 1:1 with on-site affordable floor area as defined by §2-44-085 — new units, same building, and at or above the §2-44-085 minimum unit count. Units created this way remain subject to the full terms of the ARO for as long as the building stays residential.
4 · What this page deliberately doesn't tell you
The ARO's coverage test, set-aside percentages, income tiers and in-lieu fee schedule are Title 2 provisions that the City amends on its own cycle. We publish only what we verify against the Municipal Code text we hold, so for those numbers go to the Department of Housing's current ARO rules — and treat any zoning analysis that quotes an ARO percentage without a date with suspicion.
ARO × zoning — common questions
- What triggers the ARO on a project?
- Coverage is defined in Municipal Code Chapter 2-44 (esp. §2-44-085) — outside the zoning title. Title 17 hooks into that definition: a project “subject to the requirements of the Affordable Requirements Ordinance due to an entitlement as defined in §2-44-085” is one of the approval routes into the Connected Communities bulk bonuses. For current coverage thresholds, set-aside percentages and in-lieu fees, use the Department of Housing’s ARO materials — those numbers change and we only publish what we can verify against the Code.
- Can providing ARO units on-site get me more density?
- Yes — that is the core of the Connected Communities bulk bonuses. In transit-served B-3/C-3 districts (and D-3 downtown), putting 50 / 75 / 100% of the ARO requirement on-site steps max FAR from 3.0 to 3.5 / 3.75 / 4.0 and cuts lot area per unit from 400 to 350 / 325 / 300 sq ft (§17-3-0402-B, §17-3-0403-B; §17-4-0404-C, §17-4-0405-C). Putting at least 50% of required affordable units on-site also adds 5 ft to every band of the transit height table (§17-3-0408-B).
- What is a community preservation area?
- A geography defined in §2-44-085(B) where the ARO applies with special force. Inside one, Title 17 adds typology guardrails on transit-served lots: new detached houses are prohibited in RT and RM districts (§17-2-0303-B.3), new two-flats are prohibited in RM districts (§17-2-0303-B.4), and both are prohibited in B and C districts (§17-3-0307.2) — each with escape clauses where the denser building type can’t lawfully fit. Pilsen is the canonical example.
- Can I trade parking for affordable floor area?
- In qualifying transit-served residential projects, yes: square footage freed by cutting parking beyond 50% can be replaced 1:1 with on-site affordable floor area as defined by §2-44-085, subject to the project maximizing its density and FAR standards first (§17-10-0102-B.4). Units established this way stay subject to the full terms of the ARO.