2x6 T&G Roof Decking - Diaphragm Capacity?
2x6 T&G Roof Decking - Diaphragm Capacity?
(OP)
I've got a client who wants me to provide the structural design for a park picnic shelter. Its framed of heavy timber columns supporting heavy timber beams and heavy timber wood trusses.
He's showing the whole thing sheathed in 2x6 T&G roof decking. The decking is horizontally oriented atop the truss top chords, not diagonal oriented.
The roof pitch is 9:12.
I know I read somewhere that the roof decking can not be counted on for diaphragm capacity, but for the life of me, I can't recall where I read that. I've been in my AITC book, the AWC's output on tongue and groove roof decking, as well as in the IBC, but I can't find it.
Am I crazy?
As I recall, T&G decking of this type, in this orientation, has to be sheathed in plywood in order to get diaphragm capacity from it.
Can someone guide me as to where this data is located?
He's showing the whole thing sheathed in 2x6 T&G roof decking. The decking is horizontally oriented atop the truss top chords, not diagonal oriented.
The roof pitch is 9:12.
I know I read somewhere that the roof decking can not be counted on for diaphragm capacity, but for the life of me, I can't recall where I read that. I've been in my AITC book, the AWC's output on tongue and groove roof decking, as well as in the IBC, but I can't find it.
Am I crazy?
As I recall, T&G decking of this type, in this orientation, has to be sheathed in plywood in order to get diaphragm capacity from it.
Can someone guide me as to where this data is located?






RE: 2x6 T&G Roof Decking - Diaphragm Capacity?
Nominal Capacity
Horizontal Wind = 140 plf
Diagonal Wind = 840 plf
I believe the values are in the AWC (american wood council) special design provision for Wind and Seismic. AF&PA SDPWS-year. in 2008 it is table 4.3D and there are some important notes in there.
RE: 2x6 T&G Roof Decking - Diaphragm Capacity?
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RE: 2x6 T&G Roof Decking - Diaphragm Capacity?
RE: 2x6 T&G Roof Decking - Diaphragm Capacity?
I believe the older Douglas-Fir Use Book editions have values for these diaphragms.
Mike McCann, PE, SE (WA)