Mike installs galvanized steel briding in between the floor joists on this bedroom addition project in Rocky Hill CT. Visit www.SimplyAdditions.com for more home addition videos and information. ____from this old house Bridging—those little X-shaped pieces of wood between the joists that everyone thinks are there to keep the joists from tipping over—is really there to distribute across the joist system the load put on the floor. Every 9-foot 1-inch span or greater should have wood or metal bridging, and it has to fit nice and tight. When using conventional lumber, wood bridges can be installed right away; with the metal, we nail the top to the joists but wait until we’re ready to install the finished ceiling before nailing the bottoms. This way, the joists get to dry out first, because if the joists shrink, the metal bridging will loosen. This is not a consideration, by the way, when using engineered I-joists. They can be bridged immediately.