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Re: Design of Top Plates

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Todd,

First, we show the double top plate detail, noting the splice is to
occur over a stud.  This way I "know" that I have (2) 2x flat acting
anywhere between the studs.

Second, we check the double top plate and verify it's adequacy just as
we check the adequacy of any other structural element or connection.  If
the double top plate is not adequate, it is addressed, not ignored.

Possible solutions are to reduce the length of the span of the joists
that bear on the double top plate, specify the maximum distance between
the joist and the stud or alternatively add a stud below the joist, or
simply add studs as required where joists occur (this is what we
commonly do), use a triple top plate or use a double top plate with a 3x
and a 2x.

I have seen some responses talk about load distribution through the rim
joist.  I don't see that.  This is a uniform load that occurs throughout
the length of the wall.  I can see trying to use the rim joist to
redistribute a local overstress to several studs in the proximity of the
overstress, but that is it.

Jeff Coronado, S.E.
West Covina, CA 


Speck, Todd M wrote:
> 
> John Riley's ledger question brings up a question I've had for some time
> that no one I've queried has been able to answer.
> 
> His "Studs are 2x6, D.Fir-Larch(N), @ 16".  Load from each floor is about
> 1100
> plf."
> 
> Assuming the floor trusses are spaced at 24" o.c.
> 
> My question is this: How does one justify the strength of the top plates?
> 
> For quick calculations,  assuming the roof load is 550 plf you need to
> transfer 3850 plf (550 plf roof + 1100 4th + 1100 3rd + 1100 2nd) from the
> second floor trusses to the top plates directly beneath the 2nd floor
> trusses.  with trusses spaced at 24" o.c. that's a 7700 lb point load to the
> dbl top plate.  The studs are spaced at 16" o.c. so there will be a location
> where the truss bears at midspan of the dbl top plate.
> 
> I've never had anyone be able to account for the shear and flexure stresses
> that the dbl top plates are loaded with.   Is there something I'm just not
> seeing or do engineers somehow ignore this??
> 
> All help would be much appreciated on this matter,  since I've never had
> anyone give me a decent solution to this.
> 
> -----Original Message-----
> From: John Riley [mailto:jpriley485(--nospam--at)peoplepc.com]
> Sent: Wednesday, December 27, 2000 9:20 PM
> To: seaint(--nospam--at)seaint.org
> Subject: Ledger
> 
> For a 4-story, wood-framed, senior housing facility, the building official
> requires that the stairways be sheathed with gypboard on the outside, one
> layer of 5/8", and the gypboard cannot be interrupted by ledgers.  Neither
> will he allow the floor joists to bear on the stairway walls.
> 
> Studs are 2x6, D.Fir-Larch(N), @ 16".  Load from each floor is about 1100
> plf.
> 
> Can a ledger be lag-screwed or thru-bolted through the gypboard?  What I
> have in mind is a single 2x12, D.Fir-Larch(N) with the floor joists attached
> with Simpson hangers.
> 
> Are the values in UBC Table 23-III-B-1 applicable?  Modifiable?
> 
> Is there a better way to approach the problem?
> 
> __________________
> John P. Riley, PE, SE
> Riley Engineering
> 20 Oakwood Drive, Blue Grass, Iowa 52726
> Tel & Fax:  319-381-3949
> jpriley485(--nospam--at)peoplepc.com
> 
>