Floor frame lateral blocking over support

[4thorns]

I have a question about Code R502.7 in the 2009 IRC. It states that “Joist shall be supported laterally at the “Ends” by full-depth solid blocking and so on. The Exception says that “In Seismic Design Categories ……..restraint shall also be provided at each intermediate support.

I take this to mean that blocking is required at Both Ends of the joists, and “Intermediate Support” to be defined as a support somewhere within the span of the joists.

If I am correct then I would assume that in Any Situation involving two single span joists, laterally supported at the exterior walls with a rim joist, and meeting on top of a support beam at the interior of the house, they would also require lateral resistance blocking over that support.



Again if the above is correct: If the blocking is laterally supporting the end of two joists over the support beam, does this mean that it is acceptable to only block every other joist bay assuming that the floor sheathing on top of the joists will transfer the lateral load to the next block?

 

[msquared48]

Blocking is required at every suppport, whether it is exterior or interior, single span or continuous. It's just good engineering practice.

As for blocking every other joist space, no. Block every space.



Mike McCann
MMC Engineering

 

[msquared48]

Oh, and don't copnfuse blocking with bridging.

Blocking is commonly used to transmit shear and prevent rollover.

Bridging is used to spread out a point load between the joist bvearing support to more than one joist.

Mike McCann
MMC Engineering

 

[MiketheEngineer]

I basically agree w M^2 but you could make an argument for every other "space over the I-beam.

That can be most helpful when running electrical, plumbing, HVAC, etc.

Bottom Line: I wouldn't be too worried if a few were left out - just not next to each other.

 

[4thorns]

Thanks for the replies.

"Blocking is required at every suppport, whether it is exterior or interior, single span or continuous. It's just good engineering practice."

I agree that the blocking should be there regardless. We've had varying interpretations of the the actual code though. I take the phrase "ends of the joists" to mean both ends of each joist. A colleague believes that the ends are at the exterior walls, not the other end over the beam.

I sent an email to a gentleman at the International Code Council that apparently handles code interpretation asking him this very question. Hope to get a reply tomorrow.

"I basically agree w M^2 but you could make an argument for every other "space over the I-beam.
That can be most helpful when running electrical, plumbing, HVAC, etc."

There in lies the problem. With all of this stuff in place it's a little tricky to get the blocking in if you don't put it in to begin with!

 

[MiketheEngineer]

Rim joists supply blocking at the exterior walls.

Normally joists are overlapped at interior beams. Block over the beam - not at the actual end of the beam.

Well - get ready for a bunch of pissed off plumbers, electricians and HVAC guys or do every other one....

 

[4thorns]

It's amazing to walk into an unfinished basement and see the structural damage that some of these guys cause. Not all mind you but I have seen it happen!

 

[dcarr82775]

We will sometimes use a partial depth blocking staggered high and low over interior bearing walls (assuming not a shearwall). The joists can't roll and some MEP can pass through.