Basement finishing cost: 400 to 800 sq ft, every line stated, by state
A 600 sq ft basement: about $15,700 to $19,600, typically $17,200. That's the outside walls framed and insulated along the foundation, the walls and ceiling drywalled, the walls painted, a vinyl plank floor, new outlets and an interior door, plus the contractor's overhead, profit and sales tax. A bathroom, heating and cooling, an egress window, waterproofing and permits are extra.
Anthony Hicks30+ years in construction. Updated November 5, 2026.
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What it costs
| Job | Cost |
|---|---|
| A 400 sq ft basement | $11,700 to $14,700 |
| A 600 sq ft basement | $15,700 to $19,600 |
| An 800 sq ft basement | $19,300 to $24,250 |
Totals include the contractor's overhead and profit (20%) and the state's average sales tax. Prices as of November 2026.
What’s in these numbers
Each total is a typical job, priced the way a contractor’s estimate is priced:
| 400 sq ft | 600 sq ft | 800 sq ft | |
|---|---|---|---|
| Room | 20 by 20 ft | 20 by 30 ft | 25 by 32 ft |
| Walls | 2x4 walls framed along the foundation, R13 batts | Same | Same |
| Drywall | Walls and ceiling, taped and finished | Same | Same |
| Paint | Walls, two coats | Same | Same |
| Floor | Vinyl plank over the slab | Same | Same |
| Outlets | Six | Eight | Ten |
| Door | One interior door | One interior door | One interior door |
The walls are 8 feet tall around the whole room. On top of the work:
- Overhead and profit: 20%, the standard markup on a contractor’s estimate.
- Sales tax on the materials, at the state’s average rate.
Not in them: a bathroom, heating and cooling, an egress window, waterproofing or a sump, inside partition walls, lighting, ceiling paint, trim, stairs, and permits.
Before finishing
- Water first. A basement that gets damp or leaks is fixed before walls and drywall go in; finishing over water traps it.
- An escape opening. The code calls for at least one emergency escape and rescue opening in a basement, and one in each sleeping room in it, opening to a yard or a public way (IRC R310.1). Where there isn’t one, an egress window and its well are added.
- Heat. Where the winter design temperature is below 60°F, habitable rooms need heating that keeps them at 68°F, and portable space heaters don’t count (IRC R303.10).
- Permits. Finishing a basement into living space is work the building department reviews.
What moves the price
- Size and layout. More square feet, and rooms divided by partition walls, add framing and drywall.
- A bathroom. Plumbing below the floor, and a pump where the sewer is above it, add lines of their own.
- The egress window. Cutting the foundation and digging the well is a job of its own.
- Where you live. Pick your state in the box above.
Common questions
How much does it cost to finish a basement?
About $15,700 to $19,600 for 600 square feet with the scope above, typically $17,200.
How much for a small basement?
About $11,700 to $14,700 for 400 square feet.
How much for a large basement?
About $19,300 to $24,250 for 800 square feet, typically $21,000.
Does a finished basement need an egress window?
The code calls for at least one emergency escape and rescue opening in a basement, with some exceptions such as a basement only for mechanical equipment of 200 square feet or less (IRC R310.1).