Illinois permit requirements

We have read and dated 23 permit rules across 2 jurisdictions in Illinois. They do not all say the same thing: pool thresholds alone run from 24 to 48 inches across 2 of them.

Jurisdictions: 2
Verified rules: 23
Permit always required: 14
Depends on the project: 9

Do you need a building permit in Illinois?

Usually yes, but not from Illinois itself: permits are issued by the city or county, not the state, so the rule that governs your project is the one your own jurisdiction publishes. 14 of those local rules require a permit outright, 9 depend on a size or scope condition the office publishes, and 0 need none. Illinois sets the building code those local rules derive from; your city or county sets the threshold and the fee.

Do Illinois jurisdictions agree?

Every row below is a measurement at least two Illinois jurisdictions publish, compared against each other. This is the question a statewide answer cannot settle, because the number that governs your project is the one your own city or county publishes.

Project	Published threshold	Jurisdictions	Agreement
Pool	24 to 48 inches	2	2 different numbers
Shed	81 to 150 sq ft	2	2 different numbers

0 of 2 comparable measurements are uniform across Illinois; 2 are not. Latest verification 2026-08-15.

Where Illinois jurisdictions split

The verdict for each project across the 2 Illinois jurisdictions we cover. On 2 of 13 projects they do not give the same answer, which is why a statewide answer is not one.

Project	Permit required	Depends	Across the state
Fence	1	1	Answer varies
Patio	1	1	Answer varies
Deck	2		Same answer everywhere
Electrical	2		Same answer everywhere
HVAC	2		Same answer everywhere
Plumbing	2		Same answer everywhere
Pool		2	Same answer everywhere
Roof Replacement	2		Same answer everywhere
Shed		2	Same answer everywhere
Solar	2		Same answer everywhere
Bathroom Remodel		1	Same answer everywhere
EV Charger		1	Same answer everywhere
Water Heater		1	Same answer everywhere

Building without a permit in Illinois

Illinois has no state building-permit penalty statute for private residential work; building permits and penalties are municipal. The Illinois Municipal Code authorizes corporate authorities to pass ordinances 'with such fines or penalties as may be deemed proper,' and provides that 'No fine or penalty, however, except civil penalties provided for failure to make returns or to pay any taxes levied by the municipality shall exceed $750,' with imprisonment under 65 ILCS 5/1-2-9 (only for failure to pay a fine) capped at 6 months per offense.

Penalties, the as-built path, and what the statute actually says

What you can build without a permit in Illinois

0 of the 23 answered rules across Illinois need no permit at all and 9 turn on a size or scope condition the jurisdiction publishes, by project and jurisdiction, in each office's own words.

The exemptions and conditions, jurisdiction by jurisdiction

Building code in Illinois

Illinois Residential Building Code (statewide minimum). Based on a recent edition of the International Residential Code (IRC).

Administered by Illinois Capital Development Board (CDB). Official source

Home rule municipalities, including Chicago, adopt their own building codes. Confirm with the local jurisdiction.

Most local permit thresholds derive from this code. See our sources and standards.

What each Illinois jurisdiction publishes

One line per jurisdiction, written from its own rules rather than from a state summary. This is the section that used to be a list of links, and the states with the fewest jurisdictions to compare are the ones it says the most about.

Chicago 13 rules
6 of 13 projects always need a permit and 7 turn on the size or scope of the work. Published thresholds include fence at 5 feet and patio at 30 inches.
Cook County 10 rules
8 of 10 projects always need a permit and 2 turn on the size or scope of the work. The ones that depend on the project are pool and shed. Published thresholds include pool at 24 inches and shed at 81 sq ft.