Do You Need a Permit to Build a Deck in Illinois?
What this comes down to
- The model code exempts decks up to 200 square feet, but only detached ones, so almost no deck at a house qualifies.
- Illinois issues no deck permit of its own. The village, city or county where the deck sits issues it.
- Since 2025, Illinois local codes must meet a statewide structural baseline, yet every town still writes its own permit rules.
- A deck application usually needs a plat of survey, a scaled plan and a fee. Carol Stream's deck packet lists $96.
- Expect about four inspections: pier holes, ledger bolting, framing and a final, each booked a day ahead.
- A free utility locate before digging is a separate duty from the permit, and the permit office does not make that call.
A deck permit in Illinois is a local decision, not a state one. The state sets a baseline for the code. The village or county sets the application rules. Two neighbors a mile apart can hear different answers.
This guide covers when a deck needs a permit and what the model code exempts. It then covers the application, the inspections and the utility call that comes before digging.
Does a deck need a permit in Illinois?
Almost always, yes. Illinois has no state deck permit, so the answer comes from the local building department. The Capital Development Board's state building code page sends code questions to the local official.
State law did raise the floor. Public Act 103-0510 sets a baseline. From January 1, 2025, local structural codes must be at least as strict as it. That does not create a state permit or a state exemption.
Does the 200 square foot exemption cover my deck?
Rarely. The International Code Council's model code lists four conditions in the model code exemption. A deck must be 200 square feet or less and no more than 30 inches above grade. It must also be detached from the dwelling.
The fourth condition is that the deck cannot serve the exit door the code requires. A deck off the back door fails the attachment test or the exit door test almost every time. A freestanding platform in the yard is the usual case that passes.
Even a qualifying deck is not free of rules. The same section says an exemption never authorizes work that breaks the code. Many towns also drop the exemption entirely, so the local department decides.
What does a deck permit application ask for?
A completed application, a plat of survey and scaled drawings. The Village of Carol Stream publishes a village deck packet that asks for exactly that. Its deck permit fee is $96, paid when the application goes in.
The plat must show the deck's size and its distance to each lot line. It must also show every existing accessory structure. The packet bars decks from easements. A detached deck sits at least 5 feet from the side and rear lot lines.
Those numbers belong to one village. Another town may set a different setback, fee or coverage limit. The packet shows what to expect, and the local department's own page is the one to follow.
Which inspections will a new deck have to pass?
Usually four. Carol Stream's packet lists pier holes before concrete and ledger bolting with flashing. Then come framing before boards go down, and a final. Each is booked 24 hours ahead.
The order matters because each stage hides the last. Once concrete fills a pier hole, its depth cannot be checked. The same packet sets piers at 42 inches deep. Once boards cover the framing, the hangers and ledger are out of sight.
Ledger work gets particular attention. The packet requires flashing over every ledger and bars attaching one to siding or brick veneer. The guide to deck code requirements covers the numbers behind those ledger rules.
Do I need to call before digging the footings?
Yes, and it is a separate step from the permit. Illinois utilities mark their lines for free through a free utility locate service. It asks for notice at least 3 days before digging, by calling 811 or filing online.
The permit office does not make that call for the owner. Gas, electric, water and cable lines all cross back yards. A post hole is exactly where they get hit, so wait for every mark before digging.
Does repairing a deck need a permit too?
Sometimes. Replacing worn boards over a sound frame is often treated as maintenance. Replacing a ledger, post or beam is structural and usually needs a permit. Each town draws that line differently, so ask before ordering lumber.
The walkthrough of repair versus new shows one city's answer to that question for a Naperville deck. The county side is in the guide to permit application process.
What happens if a deck is built without a permit?
The usual outcome is a stop-work order and a late permit. An inspector may ask for parts to be opened up. Depth, ledger bolts and flashing cannot be seen once the deck is finished. That makes unpermitted decks costly to legalize.
How do the model code and a village packet compare?
The table sets the model code beside the Carol Stream packet. It shows which answers come from the code and which come from the village. The last column says what to confirm locally.
| Question | Model code (2021 IRC) | Carol Stream packet | What to confirm locally |
|---|---|---|---|
| Who issues the permit | The local building official | Community Development Department | The office for your address |
| Size exemption | 200 sq ft or less, detached, 30 inches or lower | No threshold stated | Whether the exemption is adopted |
| Application | Set by the local office | Application, plat of survey, scaled plans | Paper or online, and how many copies |
| Fee | Set by a local schedule | $96 for a deck | The fee schedule in force this year |
| Pier depth | Below the local frost depth | 42 inches | The depth the village inspects to |
| Inspections | As the building official requires | Piers, ledger, framing, final | Notice needed before each visit |
What does a new deck cost once the permit is in?
A new pressure treated deck starts at $24 per square foot. A typical 12 by 16 foot deck starts at $4,495. The permit fee is a separate line because it changes from town to town. The survey is separate too.
| The work | Starting price | Wider market | What moves it |
|---|---|---|---|
| New pressure treated deck | From $24 per sq ft | $26 to $50 per sq ft | Height, footings, stairs and railing |
| Typical 12 by 16 foot deck | From $4,495 | $4,700 to $9,300 | Attachment to the house and access |
| Railing replacement | From $35 per linear ft | $40 to $100 per linear ft | Material, posts and stair runs |
What cannot be determined from the permit rules alone?
Where the lot lines really are. A fence is often off the line by a foot or more, and only the plat of survey settles it. Setbacks and easements are measured from that line.
Which amendments the town has adopted. A village can keep the model exemption, drop it or tighten it. The answer is in the adopted ordinance, not in a general guide.
And what sits underground or behind the siding. Buried lines, a brick veneer wall and a thin rim board all change how a deck can attach. Those get checked on site before the drawings are final.
Illinois deck permit questions
Do I need a permit to build a deck in Illinois?
Almost always. Illinois has no state deck permit, so the village, city or county issues it. The model code exempts only decks of 200 square feet or less. They must be no higher than 30 inches and detached. Most decks at a house do not qualify.
How does Perfect Work handle a deck permit in Illinois?
Perfect Work Remodeling & Repairs starts with the local deck packet and the plat of survey. It checks setbacks, easements and the ledger wall before drawing anything. The permit goes in with scaled plans, and inspections are booked as the work reaches each stage.
Can I build a small deck without a permit?
Only if it is detached, under 200 square feet, no higher than 30 inches and not at the exit door. That is the model code's exemption. Many towns adopt it differently or not at all, so confirm with the local building department first.
Do I need a permit to replace deck boards?
Often not. Swapping boards over a sound frame is commonly treated as maintenance. Replacing a ledger, post or beam is structural and usually needs a permit. Towns draw the line in different places, so a call to the building department settles it.
What does a deck estimate from Perfect Work include?
An estimate from Perfect Work Remodeling & Repairs prices the build. It lists the permit fee, plat check and utility locate as their own lines. Anything that could move the plan, like an easement or a buried line, is named first.
Do I have to call before digging deck footings?
Yes. Illinois utilities mark their lines free of charge. The locate service asks for 3 days' notice. Call 811 or file online. The building permit does not cover it, and the permit office does not make the call for the owner.
A deck permit that clears the first review
The permit question comes down to the address, the attachment and the size. A deck at the house needs one almost everywhere. The local department sets the details.
A visit from Perfect Work Remodeling & Repairs starts with the plat of survey and the local packet. The wall for the ledger is checked too, and the permit scope is settled with the plan. Deck work sits within its deck building and repair services, one of its listed services.
Call Perfect Work at 630-297-7888 · Book a deck check