How Much Does It Cost to Add a Dormer on Long Island in 2025?
Adding a dormer is one of the smartest ways to expand your home’s livable space without building out or up entirely. Whether you’re looking to convert an attic into a functional bedroom or simply want to add light and curb appeal, a dormer can be a game-changer. But how much does it cost to add a dormer on Long Island in 2025?
In this guide, we’ll break down average dormer prices, what factors influence the cost, and why dormers are a smart investment for Long Island homeowners.
What Is a Dormer?
A dormer is a structural extension that protrudes from a sloped roof, creating additional headroom, natural light, and usable space. Dormers can be installed as part of a new home addition or retrofitted to an existing attic or second floor.
Popular Dormer Types:
- Shed Dormer: A single flat roof that slopes downward. Great for maximizing attic space.
- Gable Dormer: The most traditional style with a peaked roof. Often used for aesthetic purposes.
- Hip Dormer: A dormer with three sloping sides—stylish and weather-resistant.
- Eyebrow Dormer: Rounded for a softer, architectural look.
Average Dormer Cost on Long Island (2025)
| Type of Dormer | Cost Range |
|---|---|
| Small Gable Dormer | $18,000 – $30,000 |
| Full Shed Dormer | $35,000 – $75,000 |
| Full Second Story w/ Dormers | $90,000 – $150,000+ |
| Custom Dormer with Bathroom | $45,000 – $100,000 |
Note: These prices include permits, framing, insulation, roofing, windows, and interior finishing. Pricing varies based on scope, materials, and accessibility.
Cost Factors That Impact Dormer Pricing
- Size of Dormer: Larger dormers require more framing, roofing, and finishing.
- Structural Modifications: Removing rafters or reinforcing the existing roof can increase labor costs.
- Plumbing & Electrical: If your dormer includes a bathroom, costs will increase due to utility work.
- Material Choices: Roofing, siding, windows, and finishes all vary in cost.
- Permitting & Zoning: On Long Island, certain towns require specific zoning approvals and variance applications—especially in historic or flood-prone areas.
- Accessibility: If scaffolding or cranes are needed, this can drive up the price.
Is Adding a Dormer Worth It in 2025?
Absolutely—especially on Long Island, where space is at a premium and property values remain high.
Benefits of Dormer Additions:
- Adds 150–300+ sq. ft. of usable space
- Improves natural lighting and ventilation
- Increases home value and curb appeal
- Great for guest rooms, home offices, or ensuite bathrooms
- Avoids a full second-story addition, saving money and time
Financing a Dormer Project in 2025
Many homeowners finance their dormer additions through:
- Home equity loans or lines of credit (HELOC)
- 203k Renovation Loans
- Refinancing with renovation funds built in
- NYS Plus One ADU Grant Program (if used for in-law units)
Ask your contractor if they work with financing partners or can assist with applications for local programs.
How Long Does It Take to Add a Dormer?
Most dormer projects take 4–10 weeks depending on the size and complexity.
- Small gable dormer: 3–5 weeks
- Full shed dormer: 6–8 weeks
- With bathroom/kitchenette: 8–10+ weeks
Permit approvals may add additional time, so it’s important to start planning early.
Get a Free Instant Estimate for Your Dormer Project
At Cascella & Sons Construction, we specialize in custom dormer builds, second-story additions, and complete home renovations across Long Island. Our family-owned team offers expert guidance, permits handled, and clean, fast construction that homeowners trust.