Home Addition Cost Calculator 2026

Home additions cost $80–$400/sqft depending on type and finish level. A 400 sqft bedroom addition averages $48,000–$80,000. A 2-car garage runs $24,000–$48,000. ADUs (accessory dwelling units) cost $90,000–$180,000 for 600 sqft but can generate $1,500–$3,000/month in rental income, typically breaking even in 5–10 years.

Most additions recover 50–80% of cost at resale, making them borderline in pure ROI terms. The value comes from: additional living space for your family, increased home value in tight markets, rental income potential (ADUs), and avoiding moving costs ($20,000–$50,000+). In hot real estate markets, additions often return 75–100% of cost.

Most homeowners use a HELOC (home equity line of credit) at 7–9% variable, or a home equity loan at 7–8% fixed. Cash-out refinance works if your rate is competitive. RenoFi loans (renovation-specific) allow borrowing based on post-renovation value. Avoid personal loans — rates are 10–20% vs 7–9% for equity-based financing.

Yes, always. Home additions require permits in all US jurisdictions. You'll need: a building permit (for structural work), electrical permit (new circuits), plumbing permit (if adding bathrooms/kitchen), and mechanical permit (HVAC extension). Permit costs: $500–$2,500 for a full addition depending on square footage and location. Never proceed without permits — unpermitted additions must be disclosed at sale, often at significant price reductions, and may need to be demolished or retrofitted to code.

A typical 400 sqft room addition takes 3–5 months from permit approval to completion. Timeline: Design and permits: 4–10 weeks. Foundation and framing: 2–4 weeks. Rough-in (electrical, plumbing, HVAC): 2–3 weeks. Insulation and drywall: 1–2 weeks. Finishing (flooring, trim, paint): 2–4 weeks. Complex additions (second story, ADU) can take 6–12 months. Delays are common due to permit timelines, subcontractor scheduling, and material lead times.

By ROI at resale: (1) Master bedroom/bathroom suite: 50–65% ROI — most requested feature by buyers. (2) Kitchen expansion: 60–75% ROI when done with the kitchen remodel. (3) ADU/in-law suite: 50–80% ROI plus rental income potential ($1,500–$3,000/month). (4) Garage addition: 65–75% ROI — high demand in cold climates. (5) Bump-out (kitchen or family room extension): 45–60% ROI at lower total cost. Sunrooms and screened porches have lower ROI (30–50%) but high personal use value.

Adding a full second story costs $150,000–$350,000+ depending on house size, design, and structural complexity. A partial second story (master suite only) runs $75,000–$150,000. The main costs: structural engineer ($2,000–$5,000), roof removal and reconstruction ($15,000–$40,000), staircase ($8,000–$20,000), and all the second-floor finish work. Second-story additions typically require temporary living arrangements ($2,000–$5,000/month for 3–6 months). Compare to building a ground-floor addition ($100–$200/sqft) — second stories cost 20–40% more per sqft due to structural complexity.

It depends on the scope. For a bump-out addition or garage/ADU built at the rear of the property, most homeowners can remain in the home with modest disruption. For larger additions that require opening the roof, tying into the foundation, or major plumbing/electrical work throughout the house, living conditions become very difficult. Plan for: heavy construction noise 7am–5pm weekdays, dust and debris infiltrating living areas (plastic sheeting helps but doesn't fully contain it), utility interruptions (water, electrical) for 1–3 days at a time during rough-in work, and loss of access to exterior doors on the affected side. For second-story additions, most contractors recommend temporary housing for 1–3 months. Budget $2,000–$5,000/month for a rental if you need to move out. Many contractors can phase the work to minimize disruption — discuss this specifically when getting bids.

Home addition costs per square foot in 2026: Basic room addition (bedroom, family room): $100–$200/sqft. Mid-range addition (with bathroom): $150–$300/sqft. High-end addition (kitchen expansion, master suite): $250–$500/sqft. Garage addition: $50–$100/sqft. ADU/in-law suite: $150–$300/sqft. Second-story addition: $200–$400/sqft (most expensive due to structural complexity). National average for all addition types: $140,000 for a 1,000 sqft addition ($140/sqft). Smaller additions (under 200 sqft) cost significantly more per sqft because fixed costs (permits, mobilization, tie-in to existing structure) are spread over fewer square feet.

Buying a new home is often cheaper than a major home addition when you factor in all costs, but it depends on your market and circumstances. Home addition costs: $100,000–$200,000 for a meaningful addition (400+ sqft). Moving costs: realtor commissions (5–6% of sale price = $18,000–$30,000 on a $400K home), closing costs on new home ($8,000–$15,000), moving expenses ($5,000–$15,000), plus the stress of moving. Total moving costs: $30,000–$60,000+. If the home you need costs $100,000 more than your current home, the addition may break even. If you love your neighborhood and the addition meets your needs, staying often wins. Consult a real estate agent to compare the math for your specific market.