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RE: Town Home Lateral Loads

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Jeff - I realize that fires kill more people than earthquakes, but this is 
not a rational code interpretation by the building official. I suggest that 
 a.) you do not separate the buildings and b.) suggest that the sheathing 
penetrating the area separation be fire treated. Otherwise, show him/her 
the section of the code regarding seismic separation which will probably 
require something like 6" between units (or more) which would kill the 
project. Most of the other building officials have interpreted it this way 
(allowing sheathing to run through). Unfortunately, it appears that the 
jurisdiction you are dealing with is not yet enlightened.

Have fun with your project!

T. William (Bill) Allen, S.E. (CA #2607)
University of Southern California, M.S.C.E., 1983
University of Texas at El Paso, B.S.C.E., 1977

Consulting Structural Engineers
32302 Camino Capistrano, #206
San Juan Capistrano, CA 92675
V (949) 248-8588•F (949) 209-2509

-----Original Message-----
From: seaint-seaosc(--nospam--at) [mailto:seaint-seaosc(--nospam--at)] On 
Behalf Of Jeff Hedman Sent: Wednesday, July 03, 2013 10:05 AM
To: seaint-seaosc(--nospam--at)
Subject: RE: [SEAINT-SEAOSC] Town Home Lateral Loads

That is how we have done it in the past. Then there are no drag forces.
However, if I do that, I don't have enough seismic separation between 
units. I think the gap is 2" between framing. So it will be less after 
sheet rockis applied.

I agree. With insufficient seismic separation and no tied between units, 
how do you provide for deflection compatibility between units and prevent 
pounding at the floor?  I think building them this way is foolishand the 
building official just doesn't understand.  He wants me to enforce a fire 
separtion between units but then ignore the seismic separtion requirement. 
In the past we have always designed these as one building with continuous 
exterior double top plates through the air gap at a minimum, if not 
continuous floor sheathingthrough the length of the building. I have never 
seen a single building built where the floor diaphragm or double top plates 
 were not continuous. This has been a recent change at this particular 
jurisdiction by the building official. An adjacent jurisdiction allows 
continuous floor sheathing and top plates at the exterior.

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