Typical deck costs in Illinois (2026)
Estimated cost (complete deck, installed) for common projects in Illinois, next to the US average. Change any option in the calculator above to price your exact project.
| Project | Illinois range | Illinois typical | US typical |
|---|---|---|---|
| 12×12 ft pressure-treated | $5,445 – $9,623 | $7,534 | $6,849 |
| 16×12 ft pressure-treated | $7,095 – $12,500 | $9,798 | $8,907 |
| 16×12 ft composite | $12,639 – $21,670 | $17,155 | $15,595 |
| 20×16 ft composite | $19,635 – $33,440 | $26,538 | $24,125 |
What changes the price in Illinois
Illinois's climate: cold, windy winters with deep frost and hot, humid summers. These local factors matter most for deck projects:
- Footings must reach below the frost line — about 42 in in the Chicago area and about 36 in across central and southern Illinois. Deep footings (or helical piles) are a bigger share of the cost here than in the South.
- Design for snow load. Decks here carry heavy snow, which can mean bigger beams or closer joist spacing than a southern deck.
- Most attached decks need a permit. Under the IRC, only small, low, freestanding decks (under 200 sq ft, under 30 in high and not serving an exit door) skip it.
Labor, sales tax and permits in Illinois
- Labor and prices: Illinois's construction cost index is 1.10 — 10% above the US average, the 9th highest of the 50 states and DC. Prices in big metros (Chicago, Aurora, Naperville) usually run above the state average, and rural areas below it.
- Sales tax: 6.25% state rate plus local taxes (10.25% in Chicago). The estimates on this page don't include it.
- Building rules: Illinois follows local codes — most cities and villages adopt the IRC, while Chicago enforces its own Chicago Building Code. Permits and inspections are handled by your city or county, so confirm requirements with your local building department before you start.
Illinois vs. other large states
16×12 ft pressure-treated deck with 40 ft of railing and 3 steps — typical cost in the 10 most populous states:
| State | Typical cost | vs. US avg |
|---|---|---|
| North Carolina | $7,927 | -11% |
| Georgia | $8,105 | -9% |
| Texas | $8,194 | -8% |
| Florida | $8,462 | -5% |
| Ohio | $8,640 | -3% |
| Michigan | $8,907 | — |
| Pennsylvania | $9,174 | +3% |
| Illinois | $9,798 | +10% |
| New York | $10,688 | +20% |
| California | $10,867 | +22% |
See all 50 states on the main deck cost calculator.
Frequently asked questions
How much does a new deck cost in Illinois?
16×12 ft pressure-treated deck with 40 ft of railing and 3 steps costs about $7,095–$12,500 in Illinois (typical $9,798), compared with $8,907 at the US average. Your exact price depends on size, materials and your contractor — use the calculator above for your own numbers.
How deep do deck footings need to be in Illinois?
Footings must go below the frost line — about 42 in in the Chicago area and about 36 in across central and southern Illinois. Your local building department sets the exact depth for your address.
Is a new deck cheaper in Illinois than in other states?
Illinois's construction cost index is 1.10, 10% above the US average and the 9th highest of the 50 states and DC. Among the 10 most populous states, Illinois ranks 8th cheapest for this project.
Does the estimate include sales tax?
No. Sales tax on materials in Illinois is 6.25% state rate plus local taxes (10.25% in Chicago). Contractors usually build it into their quotes, so compare quotes on the same basis.