> Everything structural gets built with 2x4's or prefab trusses (which are also made of 2x4's) Neither of these statements are true. 2x6's are commonly used fo

> Everything structural gets built with 2x4's or prefab trusses (which are also made of 2x4's) Neither of these statements are true. 2x6's are commonly used for a variety of reasons in vertical placement. 2x8/2x10 and even 2x12 are still common for floor joists where manufactured beams (e.g. I-beams) are not used. Trusses are not always built with 2x4s either. I'd also mention (as a recently certified firefighter) that the use of trusses in modern construction causes real headaches for the fire service: a minor failure in one part of one truss can lead the entire roof surface to become a collapse hazard. They are efficient uses of lumber but have few other merits as a construction technique.