Second Story Addition Cost Calculator (2026)
Price a second-story addition (adding a floor on top of your house) from the published cost per square foot, with design and structural engineering turned on and no new foundation, then scale the labor share by your state’s construction wage index. Estimate (non-official)
Estimated range at the U.S. median
$65,425 – $208,750
Typical estimate $132,338 ($330.84 per sq ft) Estimate (non-official)
| Hard cost | $60,000–$160,000 (typical $110,000) |
|---|---|
| Foundation adjustment | $0–$0 (typical $0) |
| Systems | $0–$0 (typical $0) |
| Design fees | $5,100–$44,000 (typical $19,800) |
| Permit | $325–$4,750 (typical $2,538) |
Sources disagree on this addition type. Treat the range as a wide planning band, not a bid.
Your renovation budget
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| Typical project estimate | – |
|---|---|
| Contingency reserve | – |
| Budget to plan for | – |
| If bids come in at the high end | – |
| Still to save or finance | – |
Get at least three written bids for the same scope, check licensing and insurance, and compare line items rather than totals. Homeowner planning guide
Contractor bid builder
The prefilled direct costs back out your overhead and profit from the typical market price above. Replace them with your own labour and material numbers to price the job.
| Direct job cost | – |
|---|---|
| Overhead | – |
| Profit | – |
| Contingency | – |
| Bid price | – |
| Gross margin / total markup | – |
| Compared with the market range | – |
Printable estimate details
Planning tool only. Confirm local code, permits, and your own costs before you send a bid. Contractor pricing guide
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Second story addition cost by size
Mid-range finish, no new foundation, architect and structural engineer on, no bathroom or kitchen, U.S. median construction wage index (1.00). Estimate (non-official)
| Size | Range | Typical | Per sq ft |
|---|---|---|---|
| 600 sq ft | $97,975–$310,750 | $197,238 | $328.73 |
| 1,000 sq ft | $163,075–$514,750 | $327,038 | $327.04 |
| 1,500 sq ft | $244,450–$769,750 | $489,288 | $326.19 |
A second story usually matches the footprint of the floor below, so a 1,000 sq ft ranch gets roughly a 1,000 sq ft second floor. The rate covers removing the roof, framing the new floor, and a new roof; a stair takes floor space on both levels. Compare against a ground-floor room addition if you have the lot space.
Types of additions
Each rate is the researched range for that project type. Finish level in the calculator selects the low, typical, or high column. Estimate (non-official)
| Type | Low–typical–high per sq ft | Sources |
|---|---|---|
| Bump-out | $82.50–$200.00 (typical $141.25) Estimate (non-official) | |
| Single-room ground-floor addition | $100.00–$250.00 (typical $187.50) Estimate (non-official) | |
| Primary suite (bedroom + bath) | $297.03–$387.20 (typical $342.11) Estimate (non-official) | |
| Sources disagree. Large conflict: CVV national cost per sq ft is about 2-2.5x HomeGuide's. | ||
| Second-story addition | $150.00–$400.00 (typical $275.00) Estimate (non-official) | |
| Sources disagree. | ||
| Attached garage | $36.70–$90.00 (typical $63.35) Estimate (non-official) | |
| Sources disagree. Sources conflict (Angi ~$30 vs HomeGuide ~$43-$150 derived). Fixr $23,000-$45,000 (no size) not used. | ||
| Sunroom | $100.00–$350.00 (typical $225.00) Estimate (non-official) Single published source. | |
| In-law suite / attached ADU | $100.00–$275.00 (typical $187.50) Estimate (non-official) | |
20x20 home addition cost
A 20×20 addition is 400 sq ft. Using a mid-range room, a slab, no extra bathroom or kitchen, the architect fee on, and a construction wage index of 1.00 (the U.S. median), the range is $43,325 to $124,750, typical $87,850 ($219.63 per sq ft). Estimate (non-official) Choose a state in the calculator to replace the index of 1.00 with that state’s OEWS construction wage index.
Second story vs ground floor
A ground-floor room is typically $187.50 per sq ft ($100.00–$250.00). A second story is typically $275.00 per sq ft ($150.00–$400.00). Estimate (non-official) The second-story choice sets foundation work to none, because the new floor area is over the existing house. See the second story addition calculator or the room addition calculator for size-by-size examples.
Home addition cost per square foot
The type table above is the cost-per-square-foot guide. Bathroom and kitchen square footage inside the addition use their own rates instead of the type rate. The Census figures below are context for new houses, not additions.
| Census region | Median | Average |
|---|---|---|
| Midwest | $194.09 | $202.13 |
| Northeast | $179.30 | $246.26 |
| South | $157.30 | $179.96 |
| West | $176.87 | $213.85 |
Census figure is for new single-family houses, not additions. Relative standard errors are published in the CHARS workbook; this table shows the median and average only.
What affects addition costs in your state
Pick a state in the calculator. The wage table uses the OEWS median hourly wage for that state. The cost formula uses the construction-and-extraction wage index, not these trade rates directly.
| Trade | Median hourly |
|---|---|
| Carpenters | $29.12 |
| Construction laborers | $22.66 |
| Electricians | $30.38 |
| Plumbers | $30.67 |
| HVAC | $29.33 |
Questions
How much does a second story addition cost?
A second-story addition typically costs $150.00 to $400.00 per sq ft (typical $275.00). A 1,000 sq ft second story with design and engineering is about $327,038 at the U.S. median wage.
Why does a second story cost more per square foot than a room addition?
The existing roof comes off, the house usually needs structural engineering, and a stair has to be added, even though no new foundation is poured. The calculator turns structural engineering on by default for this reason.
Do I need an engineer for a second-story addition?
Usually. The existing walls and foundation have to carry the new floor, so most building departments ask for engineered plans. Check with your local building department.
How much does a 20x20 home addition cost?
A 20 by 20 room is 400 sq ft. At the U.S. median construction wage (index 1.00), mid-range finish, slab foundation, no extra bath or kitchen, and the architect fee on, the range is $43,325 to $124,750 (typical $87,850, $219.63 per sq ft). Estimate (non-official). Pick a state to apply that state’s construction wage index.
How does a second-story addition compare with a ground-floor room?
The researched typical rate is $187.50 per sq ft for a ground-floor room and $275.00 per sq ft for a second story (ranges $100.00–$250.00 and $150.00–$400.00). Estimate (non-official). A second story does not add foundation area in this calculator.
Do the addition prices already include a foundation?
The guides are treated as including a basic slab. Choosing crawl, basement, or pier-and-beam adds the difference versus that slab, times local labor adjustment. Choosing none adds no foundation dollars. That slab assumption is editorial; the guides do not state it.
Why does my state change the addition estimate?
Only the labor share is scaled. With a labor share of 50%, the local factor is 1 minus that share plus that share times the state’s construction wage index (BLS OEWS, all construction and extraction occupations, versus the U.S. median).