Chicago Permit Guide · 2026

ADU / Garage Conversion Permits
in Chicago, IL

Permit fees for a ADU or garage conversion in Chicago typically run $825–$3,325. Here's exactly which permits you need, what they cost, and how long IL review takes.

Do you need a permit for a ADU or garage conversion in Chicago?

Always — converting space into a dwelling unit triggers full plan review, zoning approval, and utility sign-offs in Chicago. Permit fees for a typical $166,793 ADU or garage conversion run about $825–$3,325 (valuation-based fee plus plan review), and IL plan review typically takes 4–8 weeks (Chicago), 2–4 weeks (suburbs).

Permits you'll likely need

Building

full plan review for the dwelling conversion

Zoning / occupancy

ADU ordinance compliance and occupancy approval

Utilities

sewer, water, and electrical service connections

Fire / egress

separate egress and smoke/CO requirements

Usually exempt

Nothing meaningful — every part of a ADU or garage conversion runs through permitting. Budget for it up front.

IL permit note

Chicago Permit Requirements: Chicago has extensive permit requirements and inspections for most renovation work Chicago requires permits for almost everything—even decks and fences. The process can be slow, and inspectors are known for strict enforcement. Reddit users recommend using contractors experienced with Chicago DOB processes.

How to get ADU or garage conversion permits in Chicago

1
Confirm what triggers a permit
Building, Zoning / occupancy, Utilities, Fire / egress permits apply when the scope includes full plan review for the dwelling conversion. Cosmetic-only scopes may be exempt.
2
Budget the fee
Plan for $825–$3,325 in Chicago — a valuation-based fee on a typical $166,793 project plus plan review.
3
Apply with complete documents
Submit scope, drawings, and contractor license info to the Chicago building department. IL plan review typically takes 4–8 weeks (Chicago), 2–4 weeks (suburbs).
4
Verify it in the bid
A complete Chicago bid lists permit fees as a line item. If a bid omits permits — or suggests skipping them — analyze it before signing.

ADU / Garage Conversion permits in Chicago: FAQ

Do I need a permit for a ADU or garage conversion in Chicago?

Always — converting space into a dwelling unit triggers full plan review, zoning approval, and utility sign-offs in Chicago, IL. When in doubt, call the Chicago building department before work starts — unpermitted work can block a future sale.

How much do ADU or garage conversion permits cost in Chicago?

Expect roughly $825–$3,325 in Chicago for a typical $166,793 ADU or garage conversion. Most jurisdictions charge a valuation-based fee of about 0.5–2% of project value, plus plan review and per-trade permit minimums.

How long does a ADU or garage conversion permit take in Chicago?

Simple trade permits are often issued over the counter in Chicago. Where plan review applies, IL turnaround typically runs 4–8 weeks (Chicago), 2–4 weeks (suburbs). Submit complete drawings the first time — resubmittals are the most common cause of delay.

Who pulls the permit — me or my contractor?

Usually your contractor pulls permits for a ADU or garage conversion, and their license is attached to the work. A contractor who asks you to pull an owner's permit for contractor-performed work is shifting liability onto you — treat that as a red flag when reviewing bids.

More Chicago permit guides

Is your ADU or garage conversion bid fair?

A typical Chicago ADU or garage conversion runs $166,793. Check your contractor's bid — permits included — against live 2026 local data, free.

Chicago ADU or garage conversion costs AUDIT MY BID

Data sources: Zonda Cost vs Value 2025; Houzz 2024 Cost Guides; BLS OEWS 2023; FRED regional price indices; Reddit homeowner & contractor reports.

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ADU / Garage Conversion Permits in Chicago, IL