Home Addition cost breakdown
At a mid-range, national-average baseline, a typical home addition project is estimated at $40,000 to $120,000. The table below breaks the cost down so you can see where your project is likely to land.
| Addition type | Cost per sq ft | Typical total |
|---|---|---|
| Bump-out | $80 to $200 /sq ft | About $20,000 to $50,000 |
| Sunroom | $80 to $230 /sq ft | About $25,000 to $80,000 |
| Single room addition | $100 to $300 /sq ft | About $40,000 to $100,000 |
| In-law suite | $130 to $320 /sq ft | About $60,000 to $150,000 |
| Second-story addition | $150 to $400 /sq ft | About $100,000 to $300,000 |
Home Addition cost by project size
Most of your home addition cost scales with size. Here is the estimated national-average range at a few common project sizes.
| Addition size (square feet) | Estimated total cost | Scale |
|---|---|---|
| 200 square feet | $20,000 to $60,000 | Smaller project |
| 400 square feet | $40,000 to $120,000 | Typical project |
| 700 square feet | $70,000 to $210,000 | Larger project |
What drives home addition cost
- Addition size in square feet.
- Type: a bump-out is cheapest, a second-story addition the most expensive.
- Whether it includes a kitchen or bathroom (plumbing).
- Foundation, framing, roof, and tie-in to the existing structure.
- Finish level and any layout changes to the existing home.
- Regional labor rates and permits.
Key cost factors
Additions cost more per square foot
An addition builds everything new: foundation, framing, roof, siding, windows, plus interior systems and finishes. That is why it costs more per square foot than remodeling existing space.
Build out vs build up
Building out on a new foundation is often cheaper per square foot than building up a second story, which usually requires reinforcing the existing structure and temporary relocation during the work.
Plumbing pushes the top
Additions with a kitchen, bathroom, or in-law suite cost the most because of plumbing, fixtures, and the finishes those rooms require.