Home addition contractors in New England
An addition is new construction attached to an existing building, which means it carries every trade at once plus the hardest part — tying new structure, roof, and systems into old ones that were never built to current code.
Mid-range cost by metro
A 400 sq ft scope at a mid-range finish, with each metro's cost factor applied and a 10% contingency included. Estimates for budgeting, not quotes.
| Metro | Low | Likely | High |
|---|---|---|---|
| Portland, ME1.06× metro factor | $131k | $178k | $238k |
Estimated range — based on BLS OEWS national average wages and BLS PPI material indexes applied to Our Haus baseline unit costs, as of June 2026. Estimates are shown as a range and help set expectations. They are not a quote, a verified price, or an appraisal of what a contractor will charge.
City guides
What a complete estimate spells out
- • Whether design and engineering fees are inside or outside the price
- • Foundation type and an allowance or unit price for ledge and unsuitable soils
- • Who is responsible for zoning approvals and what happens if they are denied
- • Window and door schedule with manufacturer and series
- • How HVAC load was calculated and whether existing equipment can carry it
- • A payment schedule tied to inspected milestones, not calendar dates
- • Weather-protection responsibility during framing
Frequently asked questions
Is an addition cheaper than moving?
Sometimes. Compare the all-in addition cost — design, permits, construction, and the months of disruption — against transaction costs on a move, which typically run 8 to 10 percent of a sale price plus the price difference on the new house. In tight New England markets the addition often wins; in a soft market it often does not.
Do I need an architect?
For anything structural or anything requiring zoning relief, yes — and most municipalities will require stamped drawings for the permit anyway. A design-build contractor can supply this, but confirm who holds the stamp.