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Lateral restraint at supports for joists

R

Robert Ellenberg

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Feb 6, 2010
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210
Location
Louisiana
R502.7 states they must be supported laterally at the ends . Figure 502.2, Floor Construction, gives examples where the joists end at the perimeter but in the center it shows the joists simply lapped 3" where they rest on a girder. The drawing inplies that the girder in an intermim support and the 3" is a splice in a single girder. But you can read R502.7 to mean that the joists end sits on the girder and must be lapped and laterally supported.

What say you?
 
The wording is poor "Joists shall be supported laterally at the ends" as the word "joists" is plural, so then does the plural word "ends" refer to the plural "joists" or to the "two ends" of one particular joist?
 
The load tables are based on each joist being laterally supported at each support. This means that the joist cannot move sideways and cannot rotate from the vertical. Each joist should be positively attached to the support and to the floor or roof sheathing on top. Solid blocking between joists is assumed to keep the joists from rotating.
 
Seems as if solid blocking is required between the joists over that center beam but I wish I had a clearer understanding of "... or shall be otherwise provided with lateral support to prevent rotation."

Bill
 
Solid Blocking is probably the easiest way in most instances. This doesn't mean that you can't omit an occasional block. Joist hangers also get the job done.

There is no cookbook that describes all of the other ways to satiafy this requirement but if you can displace the top of the joist parallel to the support with tespect to the bottom of the joist it definately does not meet the intent.
 
Solid blocking is not required until "R502.7.1 Bridging"
 
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2009 IRC R502.7 "supported laterally at the ends" only.

R502.7 exception 2. says when it has to be supported at the intermediate support.

R502.7.1 Bridging, calls for lateral support for joists over 2X12 at 8' o.c.

The items listed in 502.7 to prevent rotation are not the only means possible.
 
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Nailing joists to the top of girders and nailing the sub-flooring to the top of the joists is often sufficient.
 
GH Roberts--I was wondering if someone would put that idea out there. I have done that in the past--is there agreement on whether or not it meets the specifics of the IRC?
 
The IRC provision is a prescriptive requirement. If the DPR, using sound engineering priciples, can provide the documentation that it will work, then it meets the performance requirement of the Code. Although the solid blocking works well for a firestop in the event a wall is to be built beneath the beam...
 
JBI said:
The IRC provision is a prescriptive requirement. If the DPR, using sound engineering priciples, can provide the documentation that it will work, then it meets the performance requirement of the Code. Although the solid blocking works well for a firestop in the event a wall is to be built beneath the beam...
Click to expand...
Maybe so but the IRC hasn't "prescribed" anything in this case. Simply says "supported laterally at the ends", therefore the lateral support just needs to please the BO. So I would say that toenailed to beam, nailed to subfloor, I agree with GHRoberts
 
In most cases nailing to the subfloor to the top of the foist and the joist to the beam will work but there are some situations where that may not be enough. In these unusual situations all of the joists could roll over at the same time. Such a situation is more likely to occur on a deck where there is no blocking.
 
This was a subject of debate when the 2000 first came out and there were opinions along with an article about this in the Professional Remodeler Magazing (or whatever name it was changed to). It is my understanding that this was clarified by ICC stating that solid blocking was NOT required where joists are overlapped over girders and nailed at the top and bottom. Does anyone else seem to remember this or have any of the particulars?
 
Are we talking lateral support or solid blocking? You don't have to solid block to get lateral support.

Is the question 'is solid blocking required?' (my interp: no) or 'is nailing a joist into a girder and nailing sheathing to the joist lateral support?' (my interp: porbably)
 
I agree with TimNY.. solid blocking is not required.. just lateral support.. nails to the top plate and sheating above.
 
2006 IRC

Don't leave out this blocking requirement

R502.4 Joists under bearing partitions.

And for those in a "D" seismic zone you are required intermidiate lateral restraint

R502.7 Lateral restraint at supports.

Exception: In Seismic Design Categories D0, D1 and D2, lateral restraint shall also be provided at each intermediate support.

If using and I-Joist you better check the installation instructions some require intermidiate blocking at supports
 
I'm guessing Louisiana isn't in a D seismic zone...

Yes.. if using I joists, there should be installation instrucitons at the framing inspection.
 
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