How Much Does Room Addition Cost in Illinois?
Illinois pricing is near the national average. Updated for 2026.
Room Addition Pricing in Illinois
In Illinois, the average cost for room addition is $47,250 per project, which is 5% higher than the national average of $45,000. Most Illinois residents pay between $21,000 and $84,000.
Illinois has costs that track closely with the national average, though prices can still vary between urban and rural areas within the state.
A room addition extends your home's footprint by building a new room — bedroom, family room, home office, or in-law suite. It's one of the most expensive renovations but adds significant living space and value.
Illinois vs National Average
What Affects Room Addition Cost in Illinois?
Size
Small (100 sq ft): $15,000-$25,000. Average (200 sq ft): $30,000-$50,000. Large (400+ sq ft): $60,000-$100,000+
Room Type
Basic bedroom: $20,000-$40,000. Bedroom + bathroom: $35,000-$65,000. In-law suite: $50,000-$100,000+
Per Sq Ft
Budget: $80-$150/sq ft. Mid-range: $150-$250/sq ft. High-end: $250-$400+/sq ft
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💡 Tips to Save on Room Addition in Illinois
- 1.A bump-out (extending an existing room 2-4 feet) costs $5,000-$15,000 — much less than a full addition
- 2.Building over an existing garage or patio saves on foundation costs
- 3.A dormer addition (expanding attic space) costs 30-50% less than a ground-floor addition
- 4.Act as your own general contractor if you have experience — save 15-25% on management fees
📈 Room Addition in Illinois Cost Trends (2020–2024)
Prices have increased +17.7% over the last 5 years
| Year | National Avg | YoY Change |
|---|---|---|
| 2020 | $40,134 | — |
| 2021 | $41,820 | +4.2% |
| 2022 | $44,538 | +6.5% |
| 2023 | $45,785 | +2.8% |
| 2024 | $47,250 | +3.2% |
Based on national averages adjusted for annual inflation. Actual costs vary by location and project scope.
💬 What Did You Pay?
Real costs reported by homeowners for Room Addition in Illinois
Recent Reports
Frequently Asked Questions
Does a room addition increase home value?
Yes, though ROI varies: 50-65% for a standard room addition, 60-75% for a bedroom + bathroom addition. The value also depends on whether the addition fits the neighborhood — over-improving for your area yields lower returns.
How long does a room addition take?
Typical timeline: 2-4 weeks for permits and planning. 8-16 weeks for construction. Total: 3-5 months. Complex additions with full bathrooms or custom features can take 6-12 months.
Room Addition Cost in Other States
Related Cost Guides for Illinois
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