Re: diaphragm chord wood roof

In a message dated 7/14/2008 10:09:17 A.M. Pacific Daylight Time, dmorris@bbfm.com writes:

Gerard Madden, SE wrote:
> Rich,
>
> Yes, the coil strapping is the tension element and is placed over the
> wall sheathing into your blocking at the top chord between trusses.
> The chord force will be highest at the middle of the diaphragm span as
> you know, so you can skinny it down quickly from the 8 kips you
> mentioned. You may need two straps for that region where the force is
> high. Consider using 4x10 blocking with the depth running vertical to
> give you a wide enough surface to nail your straps into.
>
> -gm
>
If the 4x10 is running horizontally (3 1/2" deep by 9 1/4" wide), then
the coil straps can be run continuous away from the upright member for
the parapet.  There will be 3 3/4" from the inner face of the vertical
2x6 to the edge of the 4x10. Should be enough room for a wide coil strap
or 2 narrow ones

The strap is usually placed on the out side of the plywood that is on the vertical face of the trusses. It is nailed to the 3 1/2" edge of the blocks. The way you described the nails would have a dual purpose (Boundary nailing and strap connection).

 

Joe Venuti
Johnson & Nielsen Associates
Palm Springs, CA

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