Floor Joist Blocking Code
In addition to providing lateral support blocking helps transfer weight to adjacent joists so that the floor acts as a unified system.
Floor joist blocking code. Joists shall be supported laterally at the ends by full depth solid blocking not less than 2 inches 51 mm nominal in thickness. Since the span is short enough that even 2x8 s would have met the code it would be pointless to put blocking at the mid span of 2x10 s since they are already more than stiff enough. Building code requires the use of blocking for floor joists that exceed 2 inches in width by 12 inches in depth.
The block is nothing more than a 2 x 6 or fire rated drywall turned flat and attached to the bottom of the first floor joists. Blocking also needs to be provided at the supporting end of a joist. The international codes i codes are the widely accepted comprehensive set of model codes used in the us and abroad to help ensure the engineering of safe sustainable affordable and resilient structures.
Fire blocking must be installed at code mandated locations in concealed cavities see typical fireblocking locations next page. It must be secured to the end of each joist with three 10 x 3 inch screws or nails. Floor joists can also be attached to a full depth header rim joist or to an adjacent stud.
It acts as a cap at the top of your framed basement wall to contain any fire in the wall long enough to alert the smoke alarms in the basement see illustration at bottom. Or by attachment to a full depth header band or rim joist or to an adjoining stud or shall be otherwise provided with lateral support to prevent rotation. Floor joist blocking the irc requires mid span blocking for joists with a width to depth ratio greater than 1 to 6 which means that even 2x12 s don t need mid span blocking.
Solid wood blocking helps reduce up or down movement and the twisting of joists. As long as sheathing is installed on the back side. Prolong the health of your framing with joist tape.
Also note the blocking between floor joists. Limiting joist movement also helps prevent gapping between deck boards for a uniform finish. Section r502 7 of the 2009 international residential code specifies that joists must be laterally supported by solid blocking that s not less than 2 inches thick and the full depth of the joist.