Home Addition Cost on the South Shore | Valcourt Remodeling
Cost Guide · Home Additions
Home Addition Cost on the South Shore
Honest, South Shore-specific cost ranges for home additions and ADUs, from bump-outs to full second-story additions. Updated for 2026.
Price Ranges
Five types of home addition
These ranges reflect full project costs, including design, permits, foundation, framing, exterior, interior finish, and mechanical work, for South Shore Massachusetts as of 2026.
Bump-Out Addition
Extends an existing room, typically a kitchen, dining room, or bedroom, by 2 to 15 feet. The least disruptive and least expensive type of addition. Can make a meaningful difference in a room that feels just a bit too small without the full complexity of a new foundation and roofline. Any lighting fixtures within the bump-out are OFCI.
Single-Room Addition (400–600 sq ft)
A full room addition such as a family room, home office, sunroom, or mudroom, added to the footprint of the home. Requires a new foundation, framing, roofline, and exterior finishes that match the existing home. The most common addition type on the South Shore. Lighting fixtures are OFCI.
Second-Story Addition
Adding a full or partial second story, the best option for homeowners who want significantly more space without expanding the footprint. In Norwell, Hanover, and Pembroke, where lots are generous but setbacks can limit ground-level expansion, a second story is sometimes the only path to the space you need. All lighting fixtures, plumbing fixtures, and bathroom hardware are OFCI.
In-Law Suite / Attached ADU
An attached accessory dwelling unit that functions as an independent living space. Increasingly popular across the South Shore for multigenerational living and rental income. Massachusetts's 2025 ADU law makes these easier to permit than ever. All plumbing fixtures, lighting fixtures, kitchen appliances, and bathroom hardware are OFCI.
Detached ADU / Garage Apartment
A fully detached accessory dwelling unit, such as a garage apartment, carriage house, or standalone cottage. The most complex ADU type from a permitting and utility standpoint, but also the most independent and potentially the highest-returning investment on larger South Shore lots. All plumbing fixtures, lighting fixtures, kitchen appliances, and bathroom hardware are OFCI.
Per-square-foot estimates are unreliable for additions
A $200/sq ft figure might be accurate in some markets, but it is not accurate on the South Shore in 2026. Foundation type, roofline complexity, finish level, and site conditions all affect cost in ways that a per-square-foot number cannot capture. The ranges above are based on real project history in this market.
South Shore Factors
What affects addition cost on the South Shore
These are the variables that most commonly affect addition project costs in this region, many of which a national cost guide would never mention.
Foundation type and soil conditions
Foundation cost varies significantly by type and soil. A poured concrete full basement adds $25,000–$50,000 over a crawl space or slab. Coastal towns with sandy or fill soils may require engineered foundations or helical piers. We assess soil conditions and foundation requirements before finalizing any addition budget.
Roofline complexity
Matching an existing roofline, especially on a cape or colonial with dormers, valleys, or a complex pitch, adds cost over a simple shed or gable roof. A well-integrated roofline is essential to making an addition look like it belongs. Cutting corners here produces an addition that looks bolted on.
Conservation Commission review
Additions within 100 feet of a wetland, stream, or coastal resource area require a Notice of Intent filed with the local Conservation Commission. This adds 4–8 weeks to the permitting timeline and requires an engineering consultant. We work directly with your engineer to navigate these filings.
Historic District Commission review
Exterior additions in Hingham and Cohasset historic districts require HDC approval before a building permit is issued. This adds 4–6 weeks and requires material selections appropriate to the period of the home. We work with your design team to prepare HDC applications.
Mechanical integration
Extending HVAC, plumbing, and electrical to a new addition is often more complex than it appears. An older home may have an undersized electrical panel, a heating system at capacity, or plumbing that needs upgrading to support the addition. These costs should be assessed before finalizing a budget.
Finish level
Addition costs can vary by $40,000–$80,000 on the same footprint depending on finish selections, including flooring, cabinetry, tile, fixtures, and trim. We help homeowners understand the cost implications of finish choices before they are locked in, not after.
Our Process
How Valcourt Remodeling approaches addition projects
Pre-design site assessment
Before any drawings are started, we walk the property with the design and engineering consultants, review zoning bylaws, identify wetland buffers, and assess the existing structure. This tells us what is feasible, what the permitting path looks like, and what the realistic budget range is before you spend money on plans.
Fixed-price contracts
We use fixed-price contracts. The price in your contract is the price you pay, barring unforeseen conditions discovered during foundation excavation or demolition, which we document and discuss with you before proceeding.
OFCI for fixtures and appliances
In additions that include kitchens, bathrooms, or in-law suites, all plumbing fixtures (faucets, showerheads, tub fillers, toilets), lighting fixtures, and kitchen appliances are owner-furnished, contractor-installed (OFCI). You select and purchase every fixture and appliance to match your exact taste; we handle all installation, rough-in, and connections. Your contract reflects labor and installation costs for these items; the equipment cost is yours to manage directly with your supplier.
Permit coordination
We handle all building, plumbing, and electrical permit applications. For projects requiring Conservation Commission or HDC review, we work with your engineering and design consultants to prepare and submit the required filings.
Architectural integration
The addition should look like it belongs, not like it was bolted on. We match rooflines, siding materials, window styles, and proportions to the existing home. This requires careful design and skilled execution, and it is the standard we hold ourselves to on every project.
FAQ
Home Addition Cost | Common Questions
Find out what your addition will cost
We offer free, no-obligation site consultations across all nine South Shore towns. We will walk your property, review your goals, and give you an honest picture of what your project will involve.