rey ceilings information needed111

huangyhg

trey ceilings information needed!!!
i work in a jurisdiction that has been struggling with the construction of trey ceilings. we are using dble 2x10's to create two main beams wall to wall and hanging dble 2x10's inside of those on hangers to create the main box of the trey, then nailing 2x4's at an angle up to a smaller box above that,it will have the ceiling joist on top of that box, it creates a two tier ceiling the ceiling joist terminate on top of this upper box in may cases sometimes the are nailed to the rafter on one end, most of the time the main beams span 16' and the center beams span 14', and my question is how do you calculate the allowable span of the 2x10's, the trey has the cj and the roof supported on the trey most of the time sometimes the roof is not braced off the beams, is there any way to find anything in writing as to how to build one, can you determine the span out of the charts in the code book and if so would the span for the beams be as a ceiling joist or header, southern yellow pine will be used, if you have any information it would be greatly appreciated, thanks
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my understanding of the approach you describe is that essentially the truss is sitting on two stub joists that form the tray.  this is ok as long as the stub joists are designed integrally with the truss and adequate lateral bracing is done, since this is a weak system in the lateral direction.  make sure the stub joists are well connected to the truss at the tray point, since the forces are trying to separate the two at that point.