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Unit pricing

Boston home addition pricing per square foot

Home Addition cost per square foot in Boston, Massachusetts in 2026.

Low

$61,200

Average

$115,600

High

$190,400

Boston crews quote about $205 – $610 per square foot.

Multiply local unit rates by your real measurements.

What drives home addition prices in Boston

Local labor, permitting and climate move Boston prices away from the national average.

Labor market

Boston labor is scarce and expensive, with a short outdoor construction season.

Permits

City permits, licensed-contractor rules and historic review are common.

Climate

Nor easters, ice dams and freeze-thaw drive roofing and insulation costs.

Boston unit pricing by material

Garage conversion$110 – $270
Sunroom$135 – $340
Bump-out$205 – $475
Single-room addition$205 – $545
Second story$270 – $680
In-law suite / ADU$245 – $610

Ways to lower your Boston price

  • Build up or bump out rather than adding a new foundation footprint.
  • Keep plumbing on the existing wet wall — moving water and waste lines is the costliest change.
  • Convert existing space (garage, attic, basement) at half the per-square-foot cost.
  • Keep the roofline simple; complex tie-ins add framing labor and leak risk.
  • Lock the design before demolition — change orders during construction carry the biggest premiums.

Boston questions

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