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Can You Build an ADU in Chicago?

ADU rules in Chicago are set by local zoning in Illinois. Many Illinois cities allow ADUs — here's what to check, plus typical costs ($183,000–$299,500 for a 700 sq ft detached unit).

Construction in Chicago runs about 8% above the Illinois average, so budget toward the higher end of these ranges.

Detached ADU (700 sq ft)

$183,000–$299,500

Garage conversion (400 sq ft)

$57,000–$104,500

Statewide protection

Local rules

What applies in Chicago

We do not yet publish a verified Chicago ordinance summary. Use this page for a planning-level cost estimate, then check Chicago's planning or building department for rules that apply to your parcel.

Estimate your Chicago ADU cost

Your property

ADU type

Estimated cost in Illinois

$183,000 – $299,500

≈ $261–$428/sq ft turnkey · midpoint $241,500

$164,200
Construction
$43,500
Design & permits
$33,800
Site work
ADU rules in Illinois are set by your city — here's what to check.
  • iSize set locally. This state leaves ADU size limits to your city — typical caps run 600–1,200 sq ft. Check your local code.
  • iParking. Set by local ordinance — commonly 1 space per ADU unless near transit.
  • iOwner-occupancy varies. Owner-occupancy rules are set locally in this state.
  • ✓Lot has room. A 700 sq ft ADU uses about 12% of your 6,000 sq ft lot — comfortably within typical coverage limits.

Rule basis: Local zoning governs — rules vary by city/county

If you rent it out

$1,175–$1,925

est. rent/mo

7.7%

gross yield

14 yrs

payback

~$17,298/yr after a 7% vacancy allowance, before financing & maintenance.

Financed over 20 yrs at 7.5%, the build is about $1,946/mo — vs ~$1,550/mo in estimated rent.

Get your detailed feasibility report →

Estimates are for planning only and are based on regional construction-cost indices and published statewide ADU statutes. Local ordinances, lot conditions and contractor pricing vary — always confirm with your city planning department and a licensed contractor.

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Other Illinois cities

AuroraNapervilleEvanstonSpringfield

Estimates are for planning only and are based on regional construction-cost indices and published statewide ADU statutes. Local ordinances, lot conditions and contractor pricing vary — always confirm with your city planning department and a licensed contractor.