Which of the following is not a common use for softwood lumber?

Softwood lumber, which comes from coniferous trees like pine, spruce, and fir, is widely used in various construction and carpentry applications due to its availability and workability. Common uses for softwood lumber include framing, roofing, and decking.

Framing is one of the most prominent uses, as softwood is strong yet lightweight, making it an ideal choice for building structures. Roofing applications often utilize softwood for trusses and sheathing due to its durability and ability to support various roofing materials. Decking is also a prevalent use because softwood can be treated to withstand outdoor conditions, making it suitable for patios and decks.

In contrast, hardwood flooring is typically made from hardwoods, which are denser and more resistant to wear and damage compared to softwoods. Hardwoods such as oak, maple, and cherry provide the durability and aesthetic qualities desired for flooring applications. Therefore, softwood lumber is generally not used for hardwood flooring, which establishes the context for identifying it as the correct answer in this case.