WORCESTER | HOLDEN | STERLING | SHREWSBURY
Custom-built four season rooms, three season sunrooms, and screened porch conversions. Built on a real foundation, insulated to Massachusetts code, and framed to last. ARM Construction builds them across Worcester County.
The sunroom category is full of confusion, and the confusion costs homeowners money. A prefabricated glass enclosure bolted onto an existing patio and a custom four season room framed on a proper foundation are sold under the same word, and they are not the same product. One of them is comfortable on a January morning in Worcester County. The other one is a porch you paid extra for.
We build the second kind. That means a foundation set below frost depth, framing with thermal breaks so the walls do not sweat and draft after two winters, insulated wall and roof cavities rather than just glazed panels, and heating sized for the room's actual load instead of a unit added at the end. Those four things are what separate a four season room from a well-lit porch, and they are the questions worth asking any contractor who quotes you one.
This is the decision that drives everything else about the project, including the budget, so it is worth being honest about how you will use the space. A three season room is enclosed but not insulated and not connected to your heating system. It is a genuinely good option if you want to extend spring and fall, screen out the bugs, and enjoy the yard from April through October. In Massachusetts, it is not a room you will use from November through March. Anyone who tells you otherwise is selling you a space heater.
A four season room is fully insulated, sits on a code-compliant foundation, uses insulated glass, and ties into heating and cooling. It works year round, and it gets appraised as living square footage, which is the other meaningful difference. A three season room is typically valued well below normal living space on a per-square-foot basis. A four season room is valued like the rest of your house. That cuts both ways, since a four season room also adds to your assessed square footage and your property taxes. If the room needs to host Thanksgiving or serve as a permanent home office, four season is the only real answer.
A lot of the work we do in this category is not new construction. It is a screened porch that has been open to the weather for twenty or thirty years and is now past its useful life, or a three season room that the family has outgrown. Converting one into a proper four season room is often the best value on the property, because the roof and the basic structure may already be there.
The catch is almost always underneath. Most screened porches in Worcester County sit on piers or a thin slab that was never built to carry an insulated, heated envelope, and plenty of them were not set to frost depth to begin with. Rot at the ledger board and the sill plate is the other common find on a porch that has spent decades exposed. We look at all of that before we talk about windows and finishes, because it determines whether the conversion is a straightforward project or a foundation job with a room on top of it. Our masonry background is a real advantage here, since we self-perform the foundation work rather than waiting on a subcontractor to tell us what we are dealing with.
A custom-built four season room generally runs $200 to $400 per square foot, which puts a typical 200 square foot room in the range of $40,000 to $80,000. A three season room runs roughly $100 to $220 per square foot. Prefabricated kit enclosures cost less than either, but they are a different product built to a different standard, and in a Massachusetts winter the difference shows.
Foundation and heating are the two line items that move the number most. Building on a sound existing slab saves thousands. A new frost-depth foundation adds $10,000 to $25,000 depending on size and site conditions. For heating, a ductless mini-split typically runs $3,000 to $7,000 installed and is usually the right choice, since it gives the room its own zone. Extending your existing ductwork runs $1,500 to $4,000, but only works if your current system genuinely has the capacity, which on a room that is mostly glass is worth calculating rather than assuming.
*Pricing estimates as of August 2026
A four season room is a small addition with an unusual amount of glass, which means it is a structural project, an insulation project, and an HVAC problem all at once. It has to carry snow load, resist frost heave, meet Massachusetts energy code, and not condense on the inside of the glass every January. That is general contracting, and it is why the results vary so much between a company that builds them and a company that installs them.
ARM Construction is run by Andrew Mercurio, a fourth-generation builder who started in masonry and grew the company into full general contracting. We self-perform the foundation, framing, and finish work. Andrew has held Massachusetts Construction Supervisor License #CS-093044 since 2011, and ARM Construction & Management Inc is a registered Massachusetts Home Improvement Contractor, registration #153199. We handle the permitting with your town and the inspection schedule, and you deal with one company from the first site walk to the last piece of trim.
We build four season rooms, sunrooms, and porch conversions in Worcester, Holden, Princeton, Sterling, West Boylston, and Boylston, along with Shrewsbury, Leominster, Westborough, Northborough, Southborough, and Grafton.
The housing stock across these towns tells you a lot about what the project will involve. Older homes in Princeton, Sterling, and Holden often have porches added decades after the house was built, on foundations that reflect the standards of whenever they went up. Postwar homes in Shrewsbury, Grafton, and West Boylston tend to have concrete patios or slabs that may or may not be usable as a base. In Worcester, tighter lots and denser housing mean setbacks are often the binding constraint rather than the foundation. Knowing which situation you are in before design starts is what keeps a project on budget.
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!
Here are the questions Worcester County homeowners ask us most about sunrooms. If yours is not here, call us at (774) 249-0221.
A three season room is enclosed but not insulated and not tied into your heating system. It works from spring through fall and is effectively unusable in a Massachusetts winter. A four season room is fully insulated, sits on a code-compliant foundation, uses insulated glass, and connects to heating and cooling, so it works in January. The other difference is how it is valued. A four season room is appraised as living square footage. A three season room typically is not, which also means it usually does not increase your property taxes the way a four season room does.
Often yes, and it is some of our favorite work. The catch is the foundation. Most screened porches in this area sit on piers or a thin slab that was never built to carry an insulated, heated envelope, and many are undersized for frost depth in Worcester County. Before anything else we look at what is under the porch, because that determines whether the conversion is straightforward or whether it needs a new foundation first. Rot at the ledger and the sill is the other common find on a porch that has been open to the weather for twenty years.
A custom-built four season room generally runs $200 to $400 per square foot, which puts a typical 200 square foot room in the range of $40,000 to $80,000. A three season room runs roughly $100 to $220 per square foot. Converting an existing screened porch usually costs less than building new if the foundation is sound, and considerably more if it is not, since a new frost-depth foundation can add $10,000 to $25,000. Heating adds cost too: a ductless mini-split typically runs $3,000 to $7,000 installed, while extending existing ductwork runs $1,500 to $4,000 if your system has the capacity.
Yes. A sunroom changes the footprint or the structure of your home, so it requires a building permit from your town, plus electrical and mechanical permits depending on the scope. A four season room also has to meet the Massachusetts energy code for insulation and air sealing, which is stricter than what most existing homes were built to. ARM Construction handles the permitting and the inspection schedule as part of the project.
A ductless mini-split is usually the right answer. It gives the room its own zone, handles both heating and cooling, and does not force your existing furnace to carry a load it was never sized for. Extending existing ductwork works if your current system has real excess capacity, but a room that is largely glass has a heat load unlike any other room in the house, so it needs to be calculated rather than guessed. A four season room heated by a space heater added at the end is a three season room with a higher price tag.
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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