http://www.homebuildingandrepairs.com/framing/floors/index.html Click on this link for more videos about floor framing, new home construction and building repairs. One of the biggest problems when building wood framed floors and installing midspan blocks will be bowed floor joists created from over or undersized blocking that will eventually create problems for floor sheathing. This seems to be a big problem with professionals, but even a bigger problem with do-it-yourselfers.