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truss blocking

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I agree with exactly what Paul said about blocking.
My two cents:
Other options are tension straps that go from the top chord to bottom chord, and mini-shear walls in-between every other or third truss (2ft heels with high shear). But take care with these options as you will apply new forces to your trusses and wall that you have to take care of.
I have had to design all of these variations for different reasons. The two main factors are truss heel height at bearing, and shear. If you have a lot of shear in your diaphragm and a tall heel height, you had better not count on the truss' measely plate and a Simpson connector to resist the out of plane shear and the overturning/racking force. Most connectors do have in the wall plane shear capacity, but this is at the base of the truss, not at the top of the truss. I do not think that most connectors are designed to do that, as a strap of even a 2 inch plate is not rigid enough to prevent the trusses from racking.
Now as that heel height gets small, say less then a foot, many engineers will argue that the truss will take that without blocking. Depends on the magnitude of the shear and your comfort level I suppose. There are engineers in my office whose opinion is that the diaphragm acts as a brace and this prevents overturning. However, I believe as the heel height increases, providing a positive shear path to the wall is necessary. BTW- every truss shop dwg I've seen has a huge statement that trusses are not designed for out of plane forces, and they are part of a system designed by others (us)....
My opinions, for what they are worth,

Andrew Kester, EI
Longwood, FL