How long will it take to build a deck? Backyard Questions & Answer › Category: Backyard Structures › How long will it take to build a deck? 0 Vote Up Vote Down Backyard Boy Staff asked 7 months ago This varies a great deal by the complexity of the project including any mishaps and weather conditions but in general a 12 x 24 foot elevated deck with a staircase and railing should take a carpenter and laborer between one and three weeks to build.