addition cost guide
How much does a home addition cost per square foot?
A home addition costs $200–$500 per square foot in most US markets and $260–$520 per square foot in major Canadian cities. Second-story additions run 20–35% more than ground-floor.
Key Takeaways
- •Ground-floor addition: $200–$500/sqft
- •Second-story addition: $260–$680/sqft
- •Includes foundation, framing, MEP, finishes
- •Permits + structural drawings required
Cost Breakdown
| Line item | Typical share / cost |
|---|---|
| Foundation | $25–$60/sqft |
| Framing + sheathing | $30–$55/sqft |
| Roofing + windows | $25–$50/sqft |
| MEP rough-in | $30–$60/sqft |
| Drywall, paint, flooring | $40–$90/sqft |
| Architect + permits | $15–$40/sqft |
Factors That Affect Your Cost
Story
Second-story additions require structural reinforcement of floors below.
Foundation type
Slab is cheapest, crawlspace mid-range, full basement most expensive.
Site access
Tight urban lots add 10–20% for crane/material handling.
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Related Questions
How long does a home addition take?
Typical builds run 4–8 months from permit to occupancy. Larger or two-story additions can stretch to 10–14 months.
Do I need an architect for a home addition?
Most jurisdictions require sealed structural drawings for additions. Many require an architect or licensed engineer.