Home Addition Cost · 2026
What a home addition costs in Illinois
Most home additions in the Chicago suburbs cost $200–$400 per square foot — roughly $60,000–$120,000 for a 300 sq ft bump-out and $150,000–$350,000+ for a master suite or full second-story addition.
Typical price tiers
| Tier | Range | What that buys |
|---|---|---|
| Bump-out (~300 sq ft) | $60,000–$120,000 | Foundation, framing, roof tie-in, and finishing one new space — mudroom, breakfast nook, office |
| Master suite / second story | $150,000–$350,000+ | Large-footprint or second-floor addition with bathroom, structural engineering, and full mechanical extension |
What moves the number
Foundation vs building up
Ground-level additions need excavation and foundation; second stories need structural analysis and temporary weather protection.
Roof tie-in
Where new roof meets old is precision work — flashed and warrantied, not just shingled.
Mechanical extension
HVAC capacity, electrical panel load, and plumbing runs to the new space.
Bathroom in the addition
A master-suite bath adds full plumbing rough-in and finish costs to the per-square-foot math.
Timeline
Additions carry the longest schedules — architectural drawings and permits come first (sealed plans are required in most villages), then construction typically runs several months depending on size. See the full GS process step by step, or how homeowners pay for a remodel.
Home Addition Cost — common questions
- How much does a home addition cost in Illinois?
-
Most home additions in the Chicago suburbs cost $200–$400 per square foot — roughly $60,000–$120,000 for a 300 sq ft bump-out and $150,000–$350,000+ for a master suite or full second-story addition.
- Do I need an architect for an addition?
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Almost always — most Chicago-suburb villages require sealed drawings for addition permits. We coordinate the architectural drawings and pull the permits as part of the project.
Want your exact number?
Free in-home estimate with an itemized scope — real figures for your actual space, not a range.