Home Addition Cost in Illinois
Updated July 2026 · Based on Illinois contractor data
$46,000
Low Estimate
$92,000
State Average
$165,600
High Estimate
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Total Cost
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Cost per Sq Ft
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Home Addition Costs in Illinois (400 sq ft)
| Addition Type | Cost in IL | Per Sq Ft | National |
|---|---|---|---|
| Bedroom | $52,900 | $132/sqft | $46,000 |
| Bathroom | $101,200 | $253/sqft | $88,000 |
| Garage | $32,200 | $81/sqft | $28,000 |
| Sunroom | $64,400 | $161/sqft | $56,000 |
| Second Story | $133,400 | $334/sqft | $116,000 |
| Adu | $105,800 | $265/sqft | $92,000 |
Home Additions in Illinois
Home addition costs in Illinois run above the national average. Higher material and labor costs in Illinois increase total project budgets.
What's Included in Home Addition Costs
- • Design and architectural drawings: $2,000–$8,000
- • Permits and inspections: $1,725–$5,750
- • Foundation: $5,750–$23,000 depending on type
- • Framing, roofing, exterior: $29–$69/sqft
- • Interior finishes: $46–$138/sqft
Planning Tips
- • Budget 10–20% contingency for unexpected issues
- • Get quotes from at least 3 licensed general contractors
- • Confirm zoning setback requirements before designing
- • Consider financing options: HELOC rates vary by state
Get Free Home Addition Quotes in Illinois
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Get Free Quotes →Frequently Asked Questions
How much does a home addition cost in Illinois?
Home additions in Illinois cost $46,000–$165,600, with an average around $92,000.
How much does it cost to add a bedroom?
Adding a bedroom in Illinois costs $52,900–$74,060 for a typical 400 sq ft room.
Is a home addition worth it?
Home additions typically recoup 50–80% of cost at resale. ADUs offer the best ROI through rental income potential.
How long does a home addition take?
A bedroom/bathroom addition takes 1–3 months. A second-story addition or ADU takes 3–6 months. Include 4–8 weeks for permitting.
What is the cheapest type of home addition?
A garage or sunroom addition is typically cheapest at $32,200–$64,400 for 400 sq ft.