Know what your home addition should cost
A 400 sq ft home addition costs $65,600 to $98,400 in 2026, about $205 per sq ft installed. Across every option it runs from $26,100 (garage conversion) to $224,000 (kitchen or bathroom addition).
Four questions gets you an itemised range, adjusted for construction wages where you live. The whole number, up front, before we ask for anything.
What home addition work costs in 2026
| Project | Typical range |
|---|---|
| Ground-floor room Bedroom, family room or office on a new slab or crawl space | $65,600 – $98,400 |
| Bump-out Small extension off an existing room, under about 150 sq ft | $55,800 – $83,600 |
| Second-storey addition Structural engineering and a temporary roof tear-off | $101,700 – $152,500 |
| Kitchen or bathroom addition New plumbing and electrical runs drive the cost | $114,800 – $172,200 |
| Garage conversion Existing structure, insulation, flooring and HVAC | $29,500 – $44,300 |
Where the money goes
Foundation and site work
$11,500 · 14% of the job
Framing and structure
$16,400 · 20% of the job
Roofing, siding and windows
$13,100 · 16% of the job
Electrical, plumbing and HVAC
$14,750 · 18% of the job
Insulation, drywall and paint
$11,500 · 14% of the job
Flooring, trim and fixtures
$9,000 · 11% of the job
Permits, design and inspections
$5,750 · 7% of the job
Home Addition cost by state
Labour is the part of this job that moves with geography. These are the same 400 sq ft project, priced against construction wages in each state.
- California $68,600 – $103,000 +4.6% vs national
- Texas $66,500 – $99,700 +1.3% vs national
- Florida $61,700 – $92,500 -6.0% vs national
- New York $68,500 – $102,700 +4.4% vs national
- Maine $62,200 – $93,400 -5.1% vs national
- Michigan $65,800 – $98,800 +0.4% vs national
- Minnesota $68,300 – $102,500 +4.2% vs national
- Missouri $64,700 – $97,100 -1.3% vs national
- Mississippi $60,600 – $90,800 -7.7% vs national
- Montana $62,100 – $93,100 -5.4% vs national
- North Carolina $63,100 – $94,700 -3.7% vs national
- North Dakota $65,300 – $97,900 -0.5% vs national
Questions homeowners ask
How much would a 20x20 addition cost?
A 20x20 addition is 400 square feet. At mid-range finishes on a ground-floor slab, expect roughly $66,000 to $98,000. Budget finishes bring that down toward $46,000; premium work pushes past $150,000.
What is the average cost of a 12x24 addition?
A 12x24 addition is 288 square feet, around $47,000 to $71,000 at mid-range finishes on a ground floor. A second-storey addition of the same size runs about 55% more because of the structural engineering and the temporary roof tear-off.
How much does it cost to add 2000 square feet to a house?
At 2,000 square feet you are building most of a house. Mid-range ground-floor work lands around $330,000 to $490,000. At that scale the foundation, roof tie-in and utility capacity often need upgrading, so get a structural engineer involved before budgeting.
What drives the cost of an addition most?
Plumbing. A bedroom or family room addition is the cheapest per square foot; adding a kitchen or bathroom runs roughly 75% more, because new supply and waste lines have to reach the addition.
Reviewed and maintained by Anchorcost. Last checked September 3, 2026. Figures are verified against this page's own calculator on every build. How these figures are worked out.