Floor Joist Blocking Requirements

Squash blocks are used to transfer load from above around the joist.

Floor joist blocking requirements. Yet it is not uncommon to find bridging not properly installed or missing all together. After several blocks the joist layout can easily be thrown out by an inch or more if you re not watching and making minor corrections as you go. Without a soffit the top plate provides the fire blocking. A deep joist is classified as one that is 4 times taller than it is wide.

For me the solid blocking takes longer to install but i tend to feel it makes things more solid don t know if that is true or not. Trusses structural composite lumber structural glue laminated members and i joists are exempted from this requirement but must be supported according to the manufacturer s recommendations. There are a couple of. An inaccessible attic space on the other hand might have a live load of only 20 psf.

This video shows you the requirements for blocking of deep joist in both natural timber and i beam and lvl joists. Or install 2 by blocking or approved sheathing along the back of the soffit. Acq treated lumber is very corrosive of hardware connectors and flashing. Floor joist bridging is critical to the structural strength of a floor as shown in figure 1.

Usually solid wood blocking or cross x wood blocking. Floor joist bridging vs blocking i used metal strap bridging for years and was never happy with the results except for the drive in type that gives the same benefit of wood x in regards to joist shrinkage. Blocking panels are used for lateral restraint of the joist to keep the ends moving from side to side to transfer load from above around the joist or for shear wall nailing from above. Joists have to be weak enough to twist when they deflect in normal use for blocking to make a difference and these joist are not going to twist at all.

I might add that in general if blocking makes a floor feel noticeably stiffer a deeper joist should probably have been used in first place. Attached pic is ceiling joist not floor but show what i typically do. Soffits provide an easy path to floor and ceiling joist bays if they re not fire blocked. Proper bridging distributes the load on the floor to other joists and over time prevents floors from sagging and squeaking do to floor joists twisting and warping.

I ve never used the metal cross blocking bridging. Failing to install either component doing so incorrectly installing them when not needed putting them in the wrong place or mixing up. If a soffit has an unfinished back block off the stud bays at the base of the soffit with 2 by material. If i think a floor needs it i typically will run a single line of blocking all the way across the room when possible.

First floor live loads have higher requirements than second floor live loads 40 pounds per square foot vs. A room used solely for sleeping might need to carry only 30 psf whereas a garage floor over a basement would need 50 psf or higher.