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RE: "The weakest link"

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Thanks for the reply, Scott.  I found a manual that suggests the same
thing, with the joists on a seat in the wall.  The detail I saw involved
using a 6" block in a wall of 10" blocks, so as to provide a 2" seat on
each side of the 6" block.

However, I also need to attach the wall to the structure to resist the
0.5 kPa (10 psf) lateral load.  I don't like the idea of weakening the
wall with a continuous beam seat.  

There doesn't seem to be a common solution yet to this requirement, so I
will probably use a simple sytem involving a couple of nails to attach
the structure to a 2x6 bolted to the face of the fire-wall.  I will
design the nails to withstand the recommended 0.5 kPa lateral load on
the wall, but no more, so that they will not resist the collapsing
structure.

Kevin


-----Original Message-----
From: Scott Maxwell [mailto:smaxwell(--nospam--at)engin.umich.edu] 
Sent: 26-Apr-06 16:24
To: seaint(--nospam--at)seaint.org
Subject: Re: "The weakest link"


Kevin:

I believe that for wood floor/roof joists to a masonry firewall, it is
common to use what is referred to as a "fire cut" (at least that is the
term that I have heard).  A "fire cut" (as I understand it) is basically
a diagonal cut from the top of the joist at about 4 to 6 inches from the
end to about the mid height of the joist at end of the joist.  In other
words, you "clip the corner" of the joist.  In theory this allows the
joist to rotate out of the beam seat in the masonry wall and fall to the
ground/floor with out pulling on the wall.

As pointed out by James Kester in response to Paul Feather's similar
post, the other way is to do a double firewall with appropriate distance
between the two walls to allow for things like seismic movement, etc.

Regards,

Scott
Adrian, MI

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