Adding a second story costs $100 to $300 per square foot on the 2026 figures Angi and HomeAdvisor both publish, with a national average of $175,000 and most homeowners spending $100,000 to $250,00023 — the two are corporate siblings, and matching figures alone don’t establish independent corroboration. HomeGuide’s page, dated October 2023, publishes $200 to $500 per square foot1; the figures are presented as dated, side by side. Everything below is the latest published data from each source.
Scope note: HomeGuide’s $175,000 national average and $100,000 to $250,000 average range are published for a 500-square-foot addition specifically; Angi and HomeAdvisor’s are general figures123.
Cost by addition size
Angi prices second-story additions across common sizes, with a published maximum for high-end builds2. HomeAdvisor’s table matches two of those rows — corporate siblings, and matching figures alone don’t establish independent corroboration3:
| Size (sq ft) | Angi average range | Angi maximum |
|---|---|---|
| 800 | $80,000–$240,000 | $400,000 |
| 900 | $90,000–$270,000 | $450,000 |
| 1,000 | $100,000–$300,000 | $500,000 |
| 1,100 | $110,000–$330,000 | $550,000 |
HomeGuide’s dated table is scoped to full second-floor additions specifically: $200,000 to $500,000 for 1,000 square feet, $240,000 to $600,000 for 1,200, $300,000 to $750,000 for 1,500, $400,000 to $1,000,000 for 2,000, and $500,000 to $1,250,000 for 2,5001. The labels differ — HomeGuide’s rows are full-floor builds, while Angi’s cover second-story additions generally — so the tables are presented separately rather than merged.
Cost by addition type
Angi publishes point estimates by type: a full second-story addition at $600,000, a partial at $300,000, converting a vaulted ceiling at $20,000, a dormer addition at $12,000 (its text puts dormers at $6,000 to $30,000), and a bonus room over the garage at $60,000 to $120,0002. HomeAdvisor likewise puts a partial addition at an average of $300,0003. HomeGuide’s dated figures: a partial second story at $100,000 to $250,000 on average, a dormer at $19,600 to $54,900, an over-garage addition at $60,000 to $200,000+, and a bump-out at $10,000 to $30,0001 — presented as published, with the dates attached.
Building up vs. building out
HomeGuide’s dated comparison puts adding a second story at $200 to $500 per square foot against $90 to $210 per square foot for a ground-level home addition and $50 to $150 per square foot for an attic conversion1. Angi’s 2026 figures put a ground-level addition at $20,000 to $80,000 on average2. See our home addition cost guide and attic conversion cost guide for those breakdowns.
Foundation and structural work
Both 2026 publishers put foundation reinforcement starting at $5,00023; HomeAdvisor adds that reinforcement and repair can reach $600,000 in its most extensive published cases3. HomeGuide’s dated figures: steel beam installation at $100 to $400 per foot including labor, materials and the structural engineer’s inspection, a pre-construction geotechnical report at $1,000 to $5,000, and structural engineering design plans at $500 to $3,000+1. HomeAdvisor separately averages a structural engineer at $550, blueprints at $1,740, and an architect’s initial fee at 8% to 20% of the project cost3.
Labor and the project team
Angi puts labor at 30% to 50% of a second-story budget, with home addition contractors charging 10% to 20% of the total project cost2. HomeAdvisor likewise puts construction managers at 10% to 20% of the total, plus hourly rates of $45 to $200 for plumbers, $50 to $150 for electricians, and $20 to $50 for painters3. HomeGuide’s dated labor table has a general contractor at $50 to $150 per hour or 10% to 20% of construction cost, an architect at $100 to $250 per hour, a structural engineer at $100 to $220 per hour, framing carpenters at $20 to $60, electricians at $50 to $130, plumbers at $45 to $150, and HVAC labor at $75 to $1501.
Staircase, roof and secondary costs
A new staircase costs $1,000 to $5,000 on HomeGuide’s dated figures1, against Angi’s $2,400 to $4,000 with high-end designs reaching $6,0002 — presented as published. Angi and HomeAdvisor both put roof replacement after the build at $4.35 to $11 per square foot23. Angi’s additional line items: room removal for demolition averaging $1,250, chimney removal averaging $4,500, and landscaping restoration at $4.50 to $12 per square foot2. HomeAdvisor adds post-construction cleaning at $300 to $7003. All three publishers note temporary housing as a real budget item during the build, without pricing it123. On timeline, HomeGuide’s dated estimate is 3 months to a year or more1, Angi puts a partial addition at three to six months and a full addition at six to 122, and HomeAdvisor suggests arranging two to 12 months of accommodations3.
Permits
Permit requirements for a second-story addition vary by municipality, so confirm with your local building authority early in planning. For budgeting, Angi and HomeAdvisor both publish a building-permit estimate of $1,200 to $2,00023, while HomeGuide’s dated page prices permits at $5 to $21 per $1,000 of project cost, or $0.16 to $0.74 per square foot1.
Related cost guides
Start with home addition cost, then compare structural engineer cost, bathroom addition, attic conversion, garage conversion and sunroom cost.
The bottom line
Budget $100 to $300 per square foot on the 2026 figures Angi and HomeAdvisor publish, or $200 to $500 per square foot on HomeGuide’s dated 2023 page — with a $175,000 national average appearing in all three. The structural unknowns, foundation reinforcement and temporary housing, are what turn a published range into your actual quote, so get a structural engineer’s assessment before comparing contractor bids.
*National and average figures are each publisher’s own published data. Sources (each fetched and read October 26, 2026; figures are each publisher’s latest published data):
1. HomeGuide, “How Much Does It Cost To Add A Second Story?” (page dated October 13, 2023) — homeguide.com/costs/cost-to-add-a-second-story
2. Angi, “How Much Does It Cost to Add a Second Story?” (updated September 21, 2026) — angi.com/articles/cost-add-second-story.htm
3. HomeAdvisor, “How Much Does a Second Story Addition Cost?” (updated June 20, 2026) — homeadvisor.com/cost/additions-and-remodels/add-new-story