PRINCETON | HOLDEN | STERLING | SHREWSBURY
More space without moving. ARM Construction designs, permits, and builds home additions across Worcester County, from the foundation to the last piece of trim. Fourth-generation builder. One company, start to finish.
Adding onto a house is not a bigger version of remodeling a room. It involves excavation, a new foundation, structural modification to the house you already live in, and tying new framing, roofing, and systems into existing construction that was probably built to a different standard. That is why most remodeling companies will not take addition work, and why the ones who do tend to subcontract the hardest parts to three different crews with three different schedules.
ARM Construction is a general contracting company built by a fourth-generation mason. Andrew Mercurio started in stone and masonry, the way his family did, and expanded into full general contracting. The practical result is that the foundation, the stonework, the framing, and the finish carpentry on your addition are handled by one company rather than coordinated across several. On a project where the foundation connection determines whether everything above it works, that matters more than most homeowners realize when they are collecting bids.
We build additions of every scale across Worcester County. Bump-outs, which extend a single room by a few feet and are often the most cost-effective way to fix a cramped kitchen or bathroom. Single-story additions that add a family room, a primary suite, a home office, or an expanded kitchen. Two-story additions that add substantial square footage on both levels at once. Second-story additions that build up rather than out when the lot will not allow expansion at grade.
We also build the specialty additions homeowners in Massachusetts are asking about most right now. In-law suites and accessory dwelling units, which state law made dramatically easier to build in 2025 and which we cover in detail on our ADU and in-law suite page. Sunrooms and four-season rooms, including conversions of existing screened porches that are past their useful life. Garage additions and conversions, both attached and detached. If your project sits somewhere between a large remodel and a true addition, we will tell you honestly which one it actually is and what each approach would cost.
Most additions in Central Massachusetts run between $150 and $350 per square foot fully finished, including design, permitting, and standard finishes. Second-story additions run higher, generally $250 to $400 per square foot, because the roof has to come off and the existing structure has to be reinforced to carry the load. These are Central Massachusetts numbers. The Boston area runs 20 to 30 percent higher for identical scope.
By project type, a bump-out of 100 to 200 square feet typically lands between $25,000 and $60,000. A single-room addition of 250 to 400 square feet runs $60,000 to $140,000. A primary suite addition runs $90,000 to $180,000. A two-story addition of 500 to 800 square feet runs $150,000 to $320,000. Where a project lands inside those ranges comes down to foundation conditions, how much structural work the existing house needs, whether the addition includes a kitchen or bathroom, and the finish level you choose. Older homes in Worcester County have a habit of producing surprises once the walls are open, which is why we look at the house before we give you a number.
Everything starts with an on-site consultation. We walk the property, look at the existing foundation and framing, check the site for access and drainage, and talk through what you are trying to accomplish. Addition projects cannot be estimated from photographs or a phone call, because the cost is driven by conditions you cannot see in a picture. What is under the house, where the utilities run, and how the existing structure was built all move the number.
From there you get a free written estimate with a scope you can actually read, then design and drawings, then permitting with your town, then construction. We handle the building department, the inspections, the material ordering, and the scheduling. You get updates as the project moves rather than having to chase them. When we hit something unexpected behind a wall or under the ground, which happens on older homes, you hear about it the same day along with what it means for the timeline and the price. No surprises at the end.
ARM Construction is based in Princeton and works throughout Worcester County. We build additions in Worcester, Princeton, Holden, Sterling, West Boylston, and Boylston, along with Shrewsbury, Northborough, Westborough, Southborough, Grafton, and Leominster.
That footprint is deliberate. We stay close enough to the work that Andrew is on your job site regularly rather than managing it by phone from two counties away, which is a difference homeowners notice on a project that runs three to six months. It also means we know the building departments, we know the towns' zoning quirks, and we know what the housing stock in each of these communities is actually built on. A 1790s farmhouse in Princeton and a 1960s ranch in Shrewsbury present completely different problems, and being local is how you know that before you start rather than after.
An addition in Massachusetts has to be built for the climate from the ground up, and the ground is where it starts. Frost depth in Worcester County means footings have to be set deep enough that seasonal freeze and thaw does not lift them, and an addition on an inadequate foundation will show you the mistake within a few winters through cracked drywall, sticking doors, and separation at the joint where new construction meets old. Getting the foundation right is not the exciting part of the project, but it is the part that determines whether everything above it holds.
The connection between new and existing construction takes the same care. Roofing and flashing at the tie-in point have to shed water and handle ice damming. Insulation and air sealing have to meet current Massachusetts energy code, which is stricter than what your existing house was likely built to, so the new space performs better than the old one and the transition between them does not create condensation problems. Siding, trim, and rooflines have to match the existing house closely enough that the addition reads as part of the home rather than something stuck onto the side of it. That last part is craftsmanship, and it is the reason people call a fourth-generation builder instead of the cheapest bid.
For a complete overview of Additions and ADUs in Massachusetts, visit our Massachusetts Home Addition Guide.
What Our Customers Say
I can't say enough good things! I needed a small finish job done at the last minute, and Andrew made it happen quickly and without any stress. The craftsmanship was perfect and everything looks amazing. I'm extremely happy and would recommend him to anyone!
Andrew and his team are detail-oriented. They are skilled and helped me understand the process of renovating my kitchen. Fantastic communication & high quality service! I am so lucky to have them and recommend them to anyone! When they built my deck, it was so fast & efficient! Call Andrew, you won't regret it
Andrew replaced a garden window in my kitchen, and a sliding door. He did a meticulous job, and went above and beyond to accommodate some special requests that I had. His attention to detail and willingness to do whatever it took to make me happy didn't go unnoticed. Will definitely use him each and every time!
Most residential additions run three to six months from the start of construction, with design and permitting adding one to three months before that depending on your town. A bump-out on an existing foundation moves faster. A two-story addition requiring a new foundation, structural modification to the existing house, and utility rerouting takes longer. Massachusetts weather also matters, since foundation work is harder to schedule between December and March. We give you a real timeline with your estimate, not a range pulled out of the air.
Yes. Any addition that changes the footprint or the structure of your home requires a building permit from your town under the Massachusetts building code, and most towns also require zoning review for setbacks, lot coverage, and height. Depending on the project you may also need electrical, plumbing, and mechanical permits, plus Conservation Commission review if the work is near wetlands. ARM Construction handles the permit process with your building department as part of the project. You are not the one filling out applications or sitting in front of the board.
Yes, and it is a large share of the work we do in Worcester County. Older homes in Princeton, Holden, Sterling, and the surrounding towns often have fieldstone or rubble foundations, framing that does not match modern dimensional lumber, settled floors, and dated electrical systems. Tying new construction into that requires knowing what you are looking at before demolition starts. Our masonry background is a direct advantage here, because the foundation connection is usually the hardest part of the job.
You can come to us with drawings already done, or you can start with nothing but an idea and we will take it from there. For straightforward additions we handle design and the drawings needed for permitting directly. For projects with significant structural change or complex site conditions we bring in a licensed engineer or architect and coordinate that work as part of the project. Either way you have one company running it and one point of contact.
Massachusetts allows one ADU by right on most single-family lots. Here is what the law permits. ...more
Additions & ADUs
August 05, 2026•7 min read
ARM Construction & Management Inc
131 Houghton Road
Princeton, MA 01541
(774) 249-0221
Licensed and insured in Massachusetts. MA CSL #CS-093044 | MA HIC Reg. #153199
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