Addition Cost Calculator
Calculate cost per square foot for your home addition
Addition Configuration
Configure your home addition to get an accurate cost estimate
Enter the total square footage of your addition
What affects the cost?
- • Structural complexity and engineering requirements
- • Local building codes and permit requirements
- • Quality of finishes and fixtures selected
- • Site conditions and access for construction
- • Seasonal material and labor pricing variations
Your Addition Estimate
Cost estimate based on current construction costs in your area
Understanding Addition Costs
Cost Factors
- • Foundation requirements
- • Structural modifications
- • Utility connections
- • Roofing integration
- • Interior finish level
- • Local permit costs
What's Included
- • All structural work
- • Basic electrical & plumbing
- • Insulation & drywall
- • Flooring installation
- • Interior trim work
- • Exterior siding match
Additional Costs
- • Architectural plans
- • Structural engineering
- • Special permits
- • Temporary utilities
- • Site preparation
- • Landscaping restoration
Why choose Ryan & Greene for your addition?
With 30+ years of New Hampshire additions behind us, we understand the complexities of integrating new space with an existing structure, from frost-depth footings to matching 1970s siding profiles. Our team handles everything from initial design to final inspection.
We pride ourselves on transparent pricing, quality workmanship, and minimal disruption to your daily life. Every addition comes with our written warranty and ongoing support.
2026 home addition cost by project type
Typical all-in ranges for completed additions in Southern New Hampshire and the Merrimack Valley, including labor, materials, and standard permits.
| Addition type | Typical total cost | What drives the price |
|---|---|---|
| Bump-out (50-150 sq ft) | $20,000 - $55,000 | Cantilevered or small-foundation expansion of an existing room |
| Single-room addition (200-400 sq ft) | $60,000 - $145,000 | Full foundation, framing, roof tie-in, and finished interior |
| Primary suite addition (400-600 sq ft) | $130,000 - $260,000 | Includes a full bath, so plumbing and finish costs rise |
| Second-story addition (600-1,000 sq ft) | $180,000 - $400,000 | Structural upgrades, stair placement, and temporary weather protection |
| In-law suite / ADU (500-800 sq ft) | $150,000 - $320,000 | Kitchen, bath, and separate entry; NH HB 577 eased local approvals |
| Garage conversion (300-500 sq ft) | $35,000 - $95,000 | Insulation, floor build-up, and HVAC are the main cost drivers |
Cost per square foot by finish level
| Finish level | Cost per sq ft | What you get |
|---|---|---|
| Basic finishes | $210 - $280 / sq ft | Builder-grade trim, laminate or LVP flooring, standard fixtures |
| Standard finishes | $280 - $370 / sq ft | Mid-range cabinetry, tile, hardwood, upgraded windows |
| Premium finishes | $370 - $500+ / sq ft | Custom millwork, stone counters, high-performance windows |
2026 New Hampshire material & labor notes
- • Framing lumber has stabilized, but engineered beams and LVL headers remain well above pre-2020 pricing.
- • Frost-depth footings (48 inches in most NH towns) add cost that warmer-climate calculators leave out.
- • Code-required air sealing and R-49 attic / R-20+ wall assemblies raise insulation budgets versus older projects.
- • Skilled-trade availability, not materials, is now the main scheduling constraint across Rockingham and Hillsborough counties.
- • Winter builds are possible here and often carry better crew availability, with modest temporary-heat and protection costs.
Home addition cost, frequently asked questions
Next step: turn this estimate into a plan
Use the number above as a budgeting range, then get at least two written bids from licensed contractors in your area. If you are in New Hampshire or northeastern Massachusetts, Ryan & Greene Construction provides free on-site estimates.