Second Story Addition Cost Calculator
Estimate the cost of building up instead of out, by square footage and finish level
Set the addition type to Second Story Addition below to price a full or partial second floor. Structural reinforcement of the existing foundation and bearing walls is the biggest variable, so treat the result as a budgeting range until an engineer reviews your home.
Addition Configuration
Configure your home addition to get an accurate cost estimate
Enter the total square footage of your addition
What affects the cost?
- • Structural complexity and engineering requirements
- • Local building codes and permit requirements
- • Quality of finishes and fixtures selected
- • Site conditions and access for construction
- • Seasonal material and labor pricing variations
Your Addition Estimate
Cost estimate based on current construction costs in your area
What a second story costs, and why
| Scope | Typical total cost | Notes |
|---|---|---|
| Partial second story (300-500 sq ft) | $120,000 - $230,000 | Over a garage or single wing, existing roof partially retained |
| Full second story (600-1,000 sq ft) | $180,000 - $400,000 | Complete roof removal, new stair, full mechanical extension |
| Two-story addition off the side | $250,000 - $500,000 | New foundation plus two finished floors, often the better value per sq ft |
Costs people forget to budget for
- • Structural engineering and stamped drawings, commonly $2,500 to $8,000
- • Foundation or footing reinforcement when the existing capacity falls short
- • Stair placement, which usually consumes 80 to 120 sq ft of first-floor space
- • Temporary weather protection while the roof is off, plus temporary housing
- • Repairing the floor below after framing, drywall, and mechanical rough-in
- • Service upgrade if the existing electrical panel cannot carry the new load
Second story additions, frequently asked questions
Next step: turn this estimate into a plan
Use the number above as a budgeting range, then get at least two written bids from licensed contractors in your area. If you are in New Hampshire or northeastern Massachusetts, Ryan & Greene Construction provides free on-site estimates.