Originally Posted by
Scott Patterson
and that the nails need to be bent over ...
He tried to tell me ... that the nails did not need to be turned down.
He's wrong on the other part, but not on the above part.
Unless the code "specifically" "requires" bending the nails over (the old South Florida Building Codes did pre-Hurricane Andrew), not only is in "not required", it is not really 'a good idea'.
What *should have been used* are those special 'truss nails' Simpson makes. They are 10d, 12d, or 16d (forgot which), but are *only* 1-1/2" long. That way, the nails do not protrude out through the other side of the truss/rafter, but provide full shear.
Bending the nails over only enlarges the hole through the wood, reducing the overall pull out resistance of the nail.
Sure, a bent over nail is more difficult for us to pull out with a hammer, but 'pull out' is not the main force to be reckoned with here, shear is. Getting back to bending the nails over, though, with the enlarged hole in the wood, there is reduced actual pull out resistance, but there is an added 'nail straightening' resistance. That nail straightening resistance affects us with our little hammers, but when the wind whips up and reaches design event loading, one tug and that nail straightens right out, and now, with the lower pull out resistance of the enlarged hole, the nail pulls right out - long before the nail shear value is reached.
After Hurricane Andrew, must testing and debating was done on this very issue, and the requirement to 'bend the nails over' was dropped from the code, because of the ultimate negative effect it had.
Use the right length nail. That solves the problem.
Too long of a nail with one of those clips does not do harm, but if you had a clip on each side, or a hanger on each side, those nails would go through and push the other clip/hanger loose - happened/happens all the time.
I posted this not too long ago, this is basically the same information.