Dormer Addition Cost on Long Island (2026)

Why we don't publish a price list: every Cape Cod is different. An 1856 pre-war frame costs a different amount to reinforce than a 1953 Levitt Cape. We give a firm fixed-price quote after the walk-through — not a range, not an estimate, an actual number you can sign.

What actually drives dormer cost

Five factors move the number more than anything else:

• Dormer size. A 16' shed dormer costs less than a 36' shed dormer. A full-width Cape dormer costs more than both because it typically triggers a full new roof, not just a raised section.
• Roof strip strategy. One-day strip-and-frame is faster and cheaper than a phased roof replacement. We default to the one-day approach on most Capes.
• Structural reinforcement. Older homes often need sistered joists, beam upgrades, or load-bearing wall work. Our in-house PE flags this at the planning stage — no surprise invoices.
• Finish level. A primary suite with spa bath costs more than a pair of bedrooms. Tile selection, millwork, cabinetry — these swing the number 15–30%.
• Town-level permit posture. Hempstead is efficient; Southampton takes longer. Permit timelines affect carrying costs, not base costs, but matter for budgeting.

How we give you a number

Our process, every time:

1. Walk-through. Frank (and sometimes Ramón) visits your property. Usually within 7 days of your call. We measure, look at the existing frame, and listen to what you want.
2. Sketch and scope. You get a one-page scope summary within 48 hours. This is not a quote — it's a mutual agreement on what we're building.
3. Preliminary drawings. Tim (our in-house AIA) drafts. A licensed PE reviews. You see drawings before we talk numbers.
4. Fixed-price quote. Formal written quote with itemized allowances. You can sign it, modify it, or walk away. No pressure, no pushy follow-ups.

Shed vs. Cape vs. full dormer — cost hierarchy

Here's the rank order, without specific numbers:

• Attic dormer (egress + headroom). Lowest cost. Mostly finish work, minimal structure.
• Partial shed dormer. Mid-range. One bedroom's worth of new space.
• Full shed dormer. Our most common job. 800–1,200 sq ft of new space.
• Cape Cod dormer conversion. Usually higher than a shed. Often triggers full new roof.
• Full second-story addition. Different category — not technically a dormer. 2–3× the cost of a shed dormer but 2–3× the space.

What we won't do

We don't take dormer jobs under $75K. Our vertically-integrated model (in-house architect, PE, permit coordinator, permanent crew) doesn't make financial sense at smaller scopes. For smaller work, we'll happily recommend two or three excellent LI carpenters we trust.