How much does it cost to add a second story to a house?
Answered by AskBaily Editorial · Updated
Short answer
A second-story addition typically runs $300-$500/sqft for the new floor in most US metros, or $500-$800/sqft in coastal California and the Northeast. A 1,000 sqft second story runs $300,000-$800,000 all-in. Full-tear-off second stories (removing the existing roof) run 30-50% more than partial additions that keep some existing roof.
In detail
A second-story addition is one of the most expensive per-square-foot residential projects because you're simultaneously doing demolition, foundation / structural reinforcement, framing, weatherproofing, and interior finish:
- Foundation and structural reinforcement ($20,000-$80,000) — a structural engineer must verify the existing foundation can carry the added dead and live load, and the floor system below must often be sistered or reinforced. In seismic zones (California, Pacific Northwest), this also means shear-wall upgrades below.
- Roof demolition and weather protection ($15,000-$40,000) — the existing roof must be removed and the house protected from weather for 2-4 weeks of framing. Rainy-season projects require temporary tarps and dehumidifiers.
- Framing + weatherproofing ($80-$150/sqft) — new second-floor framing, walls, roof, windows, siding.
- Interior finish ($100-$200/sqft) — drywall, flooring, trim, plumbing, electrical, HVAC extension.
- Temporary housing — most families cannot live in the home during a 4-8 month second-story addition. Budget $3,000-$8,000/month for rental.
Total ranges for a 1,000 sqft second story:
- Midwest / Southeast (non-coastal): $250,000-$450,000
- Inland West: $350,000-$550,000
- Coastal California / Seattle / Denver: $450,000-$750,000
- NYC metro / SF Bay: $600,000-$1,000,000+
Why it's often cheaper to build out rather than up: ground-floor additions don't require the roof removal and structural upgrade. A ground-floor addition typically runs 60-75% of the second-story per-sqft rate.
AskBaily's scoping chat asks about foundation age, lot constraints, and whether a ground-floor addition is feasible before defaulting to a pop-top second story. See /cost/home-addition for deeper breakdowns.
Sources
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