Additions Guide
Home Addition Cost in Massachusetts
By Dioclecio Gomes, Founder & Owner3 min readUpdated October 2, 2026
In Massachusetts, a single-room, ground-floor addition typically runs $35,000 to $70,000, or roughly $150 to $350 per square foot, and a second-story addition runs $300 to $500 per square foot. Nationally, Bob Vila reports an average of $48,860 and Bankrate $51,032. Permits, design, site work and a contingency are on top of the build itself.
Home addition cost is driven by size, type and finish level. National figures come from Bob Vila and Bankrate, and our own pricing from the construction services page.
How Much Does a Home Addition Cost?
Our single-room, ground-floor additions typically run $35,000 to $70,000, roughly $150 to $350 per square foot depending on finishes and complexity. Bob Vila reports a national range of $21,000 to $100,000, with an average of $48,860 and a price of $80 to $200 per square foot. Bankrate reports an average of $51,032 and $125 to $350 or more per square foot, depending on room type and finishes.
What Do Different Additions Cost?
Bob Vila gives $4,000 to $9,000 for a bump-out, $9,600 to $24,000 for a 10 by 12 foot bedroom, and $23,900 for a two-car garage. Bankrate gives $37,500 to $117,000 for a primary bedroom and about $35,000 for a bathroom addition. The spread within each type comes from foundation, finishes and how much plumbing and electrical the room needs.
How Much Does a Second Story Cost?
Our second-story additions generally run $300 to $500 per square foot, since they involve new structural support and roofing work. Bob Vila gives $100,000 to $250,000 in total, with many homeowners spending about $175,000, and says foundation support work typically costs at least $5,000 and the build takes 6 to 12 months. Plan for somewhere else to live during the build, since the house is typically unsafe to occupy.
Planning an addition?
We review your lot and goals and give you a written price after a free in-home visit.
Get a Free Addition EstimateWhat Costs Do People Forget?
Bob Vila lists permits at $400 to $1,850, architect services at $2,020 to $8,400 and site preparation at $1,276 to $5,024, and says labor and permits make up 30 to 50 percent of the price. Bankrate recommends setting aside 10% to 20% for contingencies and getting at least three contractors to quote. Our permit guide covers when a Massachusetts permit is required.
The Bottom Line
Plan on $35,000 to $70,000 for a single ground-floor room and $300 to $500 per square foot for a second story, plus design, permits and a contingency. A written scope and price keep the project predictable. Get a Free Addition Estimate
FAQ
How much does a room addition cost in Massachusetts?
A single-room, ground-floor addition typically runs $35,000 to $70,000, roughly $150 to $350 per square foot, depending on finishes and complexity.
Is it cheaper to build up or out?
Per square foot, a second story runs higher for us, at $300 to $500 against $150 to $350 for a ground-floor room, because of structural and roofing work. A ground-floor room needs a foundation and lot space, so the right choice depends on your property.
How long does a home addition take?
Bob Vila says a full second story typically takes 6 to 12 months. Smaller ground-floor additions are usually shorter, and we give a schedule in writing before work begins.