Question: how much does it cost to build a deck on the second floor?
Answer: Raised Deck Cost At $45 to $50 per square foot, a small 10 x 12-foot second-story deck made from pressure-treated lumber costs $5,400 to $6,000. Increase the size to 16 x 20 feet, and the price soars to between $14,400 and $16,000.