Everyday ToolboxHouse Addition Cost Calculator
Planning a home addition? Get a 2026 planning estimate in seconds: choose the type of addition, enter the size, pick your finish level and location. Based on national per-square-foot cost data — always get local contractor quotes before you budget for real.
Frequently Asked Questions
How much does a home addition cost per square foot in 2026?
Nationally, most additions run $80–$200 per square foot for basic work (Angi 2026 data), $200–$275 for mid-range finishes, and $300–$500+ for second-story or wet rooms like bathrooms and kitchens. High-cost metros such as Los Angeles or San Francisco can reach $420–$780 per square foot.
Is it cheaper to build out or build up?
Building out (ground level) is usually simpler to sequence when your lot allows it. Building up avoids a new foundation but needs structural engineering, roof removal and replacement, and often reinforcement of the existing structure — Angi puts second-story additions at $300–$500 per square foot nationally.
Do I need a permit for a home addition?
Almost always. Structural additions need building permits, and electrical, plumbing or mechanical work usually needs separate trade permits. Budget a planning allowance on top of construction — permit and inspection fees commonly run $500–$2,500, plus design and engineering.
How long does a home addition take?
A small addition (100–200 sq ft) typically takes 2–3 months; a medium one (300–500 sq ft) 3–5 months; a large in-law suite or second story 5–8 months. Permits, weather and material availability can extend the timeline.
How accurate is this estimate?
It is a planning estimate from national 2026 cost ranges — useful for a first budget conversation. Real bids vary with site conditions, soil, the state of your existing structure, and local labor rates, so get at least three local contractor quotes before committing.