Basement finishing is one of the most popular home improvement projects on Long Island — and for good reason. A properly finished basement adds livable space, increases home value, and on Long Island's notoriously tight real estate market, can make a meaningful difference in your home's appeal.
But what does it actually cost to finish a basement on Long Island in 2026? After finishing 580+ basements across Nassau and Suffolk Counties, here's our honest breakdown.
Long Island Basement Finishing Cost Per Square Foot
Basic
$50–$65/sq ft
LVP flooring, drop ceiling, basic recessed lighting, no bathroom
Standard
$65–$75/sq ft
LVP, drywall ceiling, upgraded lighting, half bath rough-in
Premium
$75–$85+/sq ft
Full bathroom, custom ceiling, premium LVP, built-ins
Total Cost for Typical Long Island Basements
| Basement Size | Basic Finish | Standard Finish | Premium Finish |
|---|---|---|---|
| 550 sq ft | $27,500–$35,750 | $35,750–$41,250 | $41,250–$46,750+ |
| 650 sq ft (typical) | $32,500–$42,250 | $42,250–$48,750 | $48,750–$55,250+ |
| 800 sq ft | $40,000–$52,000 | $52,000–$60,000 | $60,000–$68,000+ |
| 1,000 sq ft | $50,000–$65,000 | $65,000–$75,000 | $75,000–$85,000+ |
| 1,200 sq ft | $60,000–$78,000 | $78,000–$90,000 | $90,000–$102,000+ |
* Nassau and Suffolk County permit costs ($500–$1,500) included in estimates above.
What Drives Basement Finishing Costs on Long Island
Several factors can push your basement finishing cost above or below the typical range:
1. Bathroom Addition
Adding a half bathroom to a basement finishing project adds $6,000–$12,000 depending on how far plumbing needs to be run and whether you need an ejector pump. A full bathroom with tub/shower adds $10,000–$18,000. These are significant additions but dramatically increase the basement's functionality and resale value.
2. Egress Windows
Required for basement bedrooms. Each egress window installation costs $3,500–$8,000 including excavation, structural work, and the window well. If you want a legal bedroom in your basement, this is not optional in Nassau or Suffolk County.
3. Waterproofing
If your basement has water intrusion issues — common in Long Island due to the high water table — waterproofing before finishing adds $3,000–$12,000. Never skip this step. Finishing a wet basement without addressing the moisture is one of the most expensive mistakes Long Island homeowners make.
4. Ceiling Height
Many Long Island homes — especially Levitt-era capes — have lower ceiling heights (6'4″–7'0″). This limits your ceiling options and can require creative solutions. We do a lot of beam wrapping and low-profile drop ceiling systems for these projects.
Nassau vs. Suffolk County: Any Price Difference?
Labor costs are consistent across Long Island — there isn't a meaningful price difference between Nassau and Suffolk County for the same scope of work. Permit fees vary slightly (Nassau County permits tend to be $100–$300 more than Suffolk towns for comparable projects), but this is a minor factor in overall cost.
How to Get an Accurate Estimate
The only way to get an accurate basement finishing cost is an in-home estimate. Any contractor who quotes you over the phone without measuring is guessing. At LI Basement Pro, Dan or a senior estimator visits your home, measures precisely, assesses moisture, and discusses your goals — then provides a written itemized quote within 24–48 hours.
Get a Free Estimate for Your Basement
We visit Long Island homes Mon–Sat. Free, no-obligation estimates with written quote within 48 hours.