Home Addition Cost Calculator
Calculate 2026 home addition costs by square footage, addition type (bedroom, ADU, garage, second story), and finish level — with ROI and HELOC payment estimates.
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What Affects the Cost?
1. Cost by Addition Type
Bedroom addition: $80–$150/sqft ($32,000–$60,000 for 400sqft). Bathroom addition: $150–$300/sqft ($22,500–$45,000 for 150sqft). Attached garage (2-car): $50–$100/sqft ($24,000–$48,000 for 480sqft). Sunroom/3-season room: $80–$200/sqft. ADU/in-law suite: $150–$300/sqft. Second story: $175–$400/sqft.
2. What Drives Cost
Foundation type (slab vs crawl vs basement) can swing costs by $10,000–$40,000. Structural changes (removing load-bearing walls, moving utilities) add $5,000–$20,000. High-end finishes (granite, hardwood, custom cabinets) add 30–50%. Permit fees vary by state: $500–$3,000 for additions. Labor costs are 40–50% of total in most markets.
3. ROI by Addition Type
Bathroom addition: 50–60% ROI at resale. Bedroom/master suite: 50–65% ROI. Garage (attached): 60–80% ROI. ADU (rental unit): 80–120% ROI with rental income factored. Second story: 60–75% ROI in high-value markets. Sunroom: 40–60% ROI. All ROI figures are national averages — coastal/high-demand markets often see 10–20% higher ROI.
2026 Cost Reference Table
| Type / Option | Typical Cost Range |
|---|---|
| Master bedroom addition (400 sqft, standard) | $48,000 – $80,000 |
| Bathroom addition (150 sqft) | $22,500 – $45,000 |
| Attached garage — 2-car (480 sqft) | $24,000 – $48,000 |
| Sunroom / 3-season room (200 sqft) | $16,000 – $40,000 |
| ADU / in-law suite (600 sqft) | $90,000 – $180,000 |
| Second story (1,200 sqft) | $210,000 – $480,000 |
Frequently Asked Questions
Home additions cost $80–$400/sqft depending on type and finish level. A 400 sqft bedroom addition averages $48,000–$80,000. A 2-car garage runs $24,000–$48,000. ADUs (accessory dwelling units) cost $90,000–$180,000 for 600 sqft but can generate $1,500–$3,000/month in rental income, typically breaking even in 5–10 years.
Most additions recover 50–80% of cost at resale, making them borderline in pure ROI terms. The value comes from: additional living space for your family, increased home value in tight markets, rental income potential (ADUs), and avoiding moving costs ($20,000–$50,000+). In hot real estate markets, additions often return 75–100% of cost.
Most homeowners use a HELOC (home equity line of credit) at 7–9% variable, or a home equity loan at 7–8% fixed. Cash-out refinance works if your rate is competitive. RenoFi loans (renovation-specific) allow borrowing based on post-renovation value. Avoid personal loans — rates are 10–20% vs 7–9% for equity-based financing.
Get Home Addition Quotes + Financing
Most homeowners finance additions with a HELOC (home equity line of credit). Compare rates before hiring a contractor.
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Tips Before You Start
- ✓ ADUs (accessory dwelling units) offer the best ROI — rental income pays back in 5–10 years
- ✓ Bump-out additions (under 12 sqft) cost 20–30% less than full additions — no foundation work
- ✓ Second-story additions are the most expensive at $250–$400/sqft but maximize ROI in cities
- ✓ Garage additions recover 60–80% of cost at resale — one of the best home improvement ROI projects
- ✓ Get permits before any work starts — unpermitted additions cause major title issues at resale
Cost by State — 2026
Based on national average pricing adjusted for local labor and material costs.
Alabama
$52,800 – $91,520
$70,400
Alaska
$87,000 – $150,800
$116,000
Arizona
$58,200 – $100,880
$77,600
Arkansas
$49,800 – $86,320
$66,400
California
$88,800 – $153,920
$118,400
Colorado
$67,200 – $116,480
$89,600
Connecticut
$76,800 – $133,120
$102,400
Delaware
$64,800 – $112,320
$86,400
Florida
$111,000 – $192,400
$148,000
Georgia
$57,000 – $98,800
$76,000