Question: how much does it cost to extend a house upstairs?
Answer: A. Every house is different but here are some typical ranges: For a full 2nd story on a 2000 square foot house, the cost can range between $150,000 and $200,000. For a partial 2nd story in the 500-700 square foot range, expect to pay $90,000 to $120,000, especially if there is a new bathroom upstairs.