US ProPaint & Renovation has been building home additions in Cohasset, MA and across the South Shore for more than two decades. Most Cohasset homeowners budget between $120 and $350 per square foot for a fully permitted addition — the range shifts based on project type, coastal site conditions, and how much structural work the existing home requires. Call (800) 964-0717 for a free, no-obligation estimate.
By JR Reis, Owner & Founder · Last updated 3rd July 2026
A home addition is new construction attached to an existing house that permanently expands its livable square footage. Unlike a renovation — which reshapes space you already have — an addition creates entirely new rooms, stories, or building footprints. The addition ties into the existing structure at the foundation, framing, roofing, and utility levels, which is why a licensed general contractor, rather than a finish remodeler, typically leads the work.
On Cohasset’s South Shore, additions frequently expand undersized kitchens, create primary suite square footage on a second floor, or push out the back of a cape or colonial to accommodate a growing family. Because many Cohasset homes were built in the mid-20th century, additions often also involve upgrading older mechanicals — electrical panels, plumbing stacks, or HVAC — to handle the added load before the new space is framed in.
Most home additions Cohasset MA homeowners request fall into three main categories, each with its own cost range and site complexity.
Room additions extend a single-story footprint outward from the existing structure. They are the most common request on the South Shore — typically a primary bedroom suite, a sunroom, or a family room off the back of the house. A room addition requires its own foundation work, framing, roofing integration, and full interior finish-out. When executed well, it matches the existing siding and trim so closely that it looks original to the home. As a room addition company Norfolk County contractors compete to serve, we focus on that seamless integration at every project.
Second-story additions are popular among Cohasset homeowners who want to roughly double their living area without losing yard space. These projects are structurally intensive — the existing first-floor walls and foundation must be evaluated and often reinforced before the second story goes up. We complete this structural assessment on every second-story quote because an undersized first-floor structure is the leading cause of cost overruns and timeline delays on South Shore addition projects.
Bump-out additions are smaller extensions — typically 100 to 300 square feet — that push one room outward by several feet. They are a cost-effective way to expand a cramped kitchen, widen a primary bath, or add a laundry nook without a full room addition footprint. Bump-outs do not always require new foundation work, which keeps labor costs meaningfully lower.
Our full home additions service page covers the complete planning-through-completion process for all three types.
The best home addition contractor on the South Shore MA will provide an itemized quote, not a per-square-foot ballpark that leaves out permitting fees, utility connections, and interior finish work. That said, here are realistic installed ranges for Norfolk County based on what we see in the field:
Addition Type | Typical Installed Range |
Bump-out (100–300 sq ft) | $40,000 – $90,000 |
Single-room addition (300–600 sq ft) | $90,000 – $185,000 |
Second-story addition | $150,000 – $350,000+ |
Cohasset and the broader South Shore skew toward the upper half of national averages, primarily because of local labor costs, coastal building requirements, and the complexity of tying new construction into older home stock. Properties near Cohasset Harbor or along Jerusalem Road may also require Conservation Commission review before a permit is approved — a step that can add six to eight weeks to the planning timeline and should be factored into any contract discussion before work begins.
Connecting interior finish-out to a new addition is also where costs add up fastest. Our kitchen renovation and bathroom renovation pages break out what those interior scopes typically cost on the South Shore so you can plan your full budget before we meet.
As a home addition contractor South Shore MA homeowners have relied on for over 20 years, we recommend building a 10–15% contingency into any quoted price — especially in historic or coastal Cohasset neighborhoods, where hidden conditions like undersized wiring, old insulation types, and crawlspace moisture are common findings once demo begins.
For most Cohasset homeowners, the total timeline from first conversation to a final Certificate of Occupancy runs four to eight months. Here is how that typically breaks down:
Design and permitting: 6–12 weeks. The Cohasset Building Department processes permits through its electronic permitting portal. Additions trigger Building Commission review, and properties near wetlands, the coast, or within the Historic District may also require Conservation Commission and Zoning Board of Appeals sign-off. We manage permitting in-house on every addition project and coordinate across all relevant town departments so you are not chasing approvals across multiple offices.
Construction: 8–16 weeks. A bump-out in good structural conditions can reach completion in roughly two months. A second-story addition typically runs three to four months of active construction. Coastal weather on the South Shore — particularly nor’easters and sustained rain between November and March — is a real scheduling factor that we account for in every project plan.
Inspections and punch list: 2–4 weeks. Cohasset requires phased inspections at foundation, rough framing, rough MEP, and final stages before a Certificate of Occupancy is issued. We schedule these proactively so inspections do not sit in a queue and stall your timeline.
The answer to “how long does a home addition take to build?” always hinges on how quickly permitting moves. Working with a contractor who knows Cohasset’s permitting process specifically — rather than one learning it for the first time on your project — is the single biggest schedule protection available.
Any construction regulated by the Massachusetts State Building Code requires a building permit in Cohasset, and home additions are among the most permit-intensive project types the Building Department reviews. Only a licensed Construction Supervisor can pull permits for work on another person’s property in Massachusetts — a requirement the Cohasset Building Department enforces on every additional application.
Cohasset has also adopted the Stretch Energy Code, which sets higher insulation, air-sealing, and thermal envelope standards than the base Massachusetts code. Additions built to Stretch Energy Code requirements cost modestly more upfront in insulation and window specs but consistently deliver lower heating and cooling bills — a real operational benefit for older Cohasset homes that were never insulated to modern standards. You can review Cohasset’s full building permit requirements and the Cohasset Building Department FAQ to understand what a new addition application involves before we submit on your behalf.
We also recommend confirming zoning setbacks and lot coverage allowances before finalizing your additional footprint, particularly in Cohasset’s R-A and R-B districts where side-yard setbacks can be tighter than they appear on a site plan.
We are a home addition company near Cohasset with more than 23 years of active renovation experience on the South Shore. Owner JR Reis runs every project personally — a crew of ten licensed tradespeople handles framing, roofing, siding, and interior finish work under one contractor, eliminating the coordination gaps that routinely blow timelines when a project is split across multiple subs.
As a past customer in Hingham noted after their deck replacement and kitchen renovation: JR was very thoughtful during initial discussions and came up with creative ideas to resolve structural challenges — the same approach we bring to every addition project.
Being the right contractor for second story or room addition Norfolk County homeowners trust also means knowing the local conditions: that a 1950s cape in Cohasset will likely have undersized exterior walls that need to be furred out to meet Stretch Energy Code requirements, or that a second-story addition on a slab foundation demands a different structural approach than the same project on a full basement. That knowledge comes from doing the work here — not from reading about it.
Our deck construction, siding repair and replacement, and exterior painting services in Cohasset integrate directly into our additional finish-out work, so the new addition matches the existing home in materials, trim profile, and color without requiring a separate contractor.
As a home addition builder near me for Norfolk County and Plymouth County homeowners, we serve Cohasset, Hingham, Scituate, Norwell, Marshfield, Duxbury, Hanover, and Weymouth, as well as Quincy, Braintree, Canton, and the Boston metro. If you are unsure whether we cover your address, call and we will confirm.
Room additions extend the first-floor footprint outward and include full foundation, framing, roofing, and interior finish work. Second-story additions build upward from the existing first floor and require a structural evaluation of the walls and foundation before any construction begins. Bump-outs are smaller extensions — typically one room pushed outward by several feet — that may not require new foundation work, making them a cost-effective option for expanding a kitchen or bathroom without committing to a full additional footprint.
Cohasset and South Shore home additions typically range from $40,000 for a small bump-out to $350,000 or more for a full second-story addition. Single-room additions in the 300–600 sq ft range generally run $90,000–$185,000 fully installed, including permitting, framing, roofing, and interior finish-out. Coastal location, structural conditions of the existing home, and finish-level selections are the primary cost variables on the South Shore.
Yes. All construction regulated by the Massachusetts State Building Code requires a building permit in Cohasset, and home additions are among the most permit-intensive project types. The Cohasset Building Department requires electronic permit applications, and the Building Commission must approve all applications before any work may begin. Coastal properties may also require Conservation Commission review. US ProPaint & Renovation handles all permitting in-house on additional projects.
Most Cohasset home additions take four to eight months from initial planning through the final Certificate of Occupancy. Permitting and design typically take six to twelve weeks, active construction runs eight to sixteen weeks depending on scope, and final inspections and punch-list work add two to four weeks. Second-story additions and coastal properties subject to Conservation Commission review sit at the longer end of that range.
Yes — home additions consistently add value on the South Shore, where lot sizes are fixed and demand for larger homes remains high. Room additions and second-story additions that add bedrooms or primary suites typically return 50–80% of construction cost in appraised resale value, and often more in a high-demand market like Cohasset. An addition that brings a home from three to four bedrooms can move it into a meaningfully different buyer pool and price tier entirely.
US ProPaint & Renovation 175 Derby St STE 4 Hingham, MA 02043 Phone: (800) 964-0717 Hours: Monday–Friday, 8:00 AM – 4:00 PM Serving Cohasset, Hingham, Scituate, Norwell, Marshfield, Duxbury, Hanover, and the full South Shore.
