In Illinois, a standard 300 sqft deck runs roughly $20,442–$29,369 depending on material. Labor runs 5% above the national average, and permits typically cost about $300. Frost-line footings add 8–12% to the build.
Cost by material — 300 sqft deck in Illinois
Standard 12×25 deck, 3–5 ft off ground, composite balusters, one stair run. Includes framing, footings, railing, stairs, permit, and 8% contingency.
Pressure-Treated Pine
15–20 yrs · Stain every 2–3 yrs
$68/sqft
$20,442
Cedar / Redwood
20–25 yrs · Seal every 2–3 yrs
$76/sqft
$22,729
Composite (Trex, TimberTech)
25–30 yrs · Rinse yearly
$88/sqft
$26,500
PVC / Cellular
30+ yrs · Rinse yearly
$98/sqft
$29,369
Ipe / Cumaru Hardwood
40+ yrs · Oil annually (optional)
$105/sqft
$31,362
What drives cost in Illinois
Labor (105% of national avg). Labor runs close to the US average.
Permits (~$300). Most Illinois municipalities require a building permit for any deck over 30 inches. Inspections typically happen at the footing and final stages.
Frost-line footings. Illinois's frost line forces footings 36–48 inches deep, adding roughly $50–80 per pier and extra concrete volume. Budget 8–12% more than warm-climate equivalents.
Materials. Pressure-treated pine is the cheapest per sqft; composite (Trex, TimberTech) is 2–3× more but almost maintenance-free. Most Illinois homeowners picking a mid-tier build land on composite.
Illinois deck cost — FAQ
How much does a deck cost in Illinois?+
In Illinois, a standard 300 sqft deck runs about $20,442 for pressure-treated pine to $31,362 for ipe hardwood. Most homeowners picking mid-tier composite (Trex, TimberTech) land near $26,500 — roughly $88 per square foot installed.
Do I need a permit for a deck in Illinois?+
Most Illinois municipalities require a building permit for any deck over 30 inches off the ground or attached to a house. Permit fees typically run around $300. Inspections usually happen at the footing stage and at final.
What's the cheapest deck material in Illinois?+
Pressure-treated pine at about $68 per square foot installed. Cedar is the next step up at $76/sqft. For long-term cost-of-ownership (accounting for stain and maintenance), composite at $88/sqft often wins past year 12.
How much is labor for a deck in Illinois?+
Illinois labor runs 105% of the US average — 5% above the national baseline. Labor accounts for 40–55% of total deck cost. On a 300 sqft composite build, that's roughly $12,720 of the total.
Do I need frost-line footings in Illinois?+
Frost-line footings push 36–48 inches deep in this state, adding roughly 8–12% to total cost vs warm-climate equivalents. Most Illinois jurisdictions require footings below the local frost line, verified at inspection.
Does a deck add home value in Illinois?+
Yes. Nationally, a new deck returns 50–70% of its cost at resale. In Illinois's climate, an outdoor living space is especially valued despite the shorter usable season. Real estate appraisers typically credit deck value at 50–65% of installed cost; buyers tend to value it even higher when a property is actively listed.
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