Load Path to Roof Diaphragm w/ Overhang Trusses - See Detail
Load Path to Roof Diaphragm w/ Overhang Trusses - See Detail
(OP)
Interested in how others typically transfer load from exterior wall to roof diaphragm when dealing with trusses overhanging a porch. Please see attached detail, initial plan is to use the jack trusses as drag struts and sheath the porch ceiling with 3/8" plywood. Even with the high wind it is exposed to, the force per truss doesn't seem that much <200#, do you think in this scenario it is even needed to specify this load to the truss manufacturer? wouldn't a typical spike plate more than take care of this load?
If this is not a reliable load path any suggestions on bracing or other means of getting the wall load to the roof diaphragm?
If this is not a reliable load path any suggestions on bracing or other means of getting the wall load to the roof diaphragm?






RE: Load Path to Roof Diaphragm w/ Overhang Trusses - See Detail
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: Load Path to Roof Diaphragm w/ Overhang Trusses - See Detail
My confusion comes from you talking about using the jacks as drag struts. Drag forces act in line with the member, so that comment implies you are transferring load perpendicular to the exterior wall. If that is the case, ignore what I said above.
RE: Load Path to Roof Diaphragm w/ Overhang Trusses - See Detail
RE: Load Path to Roof Diaphragm w/ Overhang Trusses - See Detail
RE: Load Path to Roof Diaphragm w/ Overhang Trusses - See Detail
The concept that woodman88 suggested would work, except I would sheathe that truss so that it is more 'wood wall' than truss.
When specifying special truss conditions, anything beyond load type, location and magnitude and the truss jockeys go to lunch. Conversations about shear, drag etc. are way over their heads generally speaking.
RE: Load Path to Roof Diaphragm w/ Overhang Trusses - See Detail
I also like Bigmig's design, it is what I have done in the past many times for shear transfer from the roof diaphragm into the shear wall. Now for out-of-plane lateral loading of the wall, you can use your concept of using the porch roof as a diaphram or each bottom chord of the truss will really collect that load at 2' o.c. Make sure that connection at the T.O. CMU to the truss is designed for that force also. The problem is at the left side of your detail, at the truss heel, that truss plate is not designed for this drag force to get it up into the top chord and into your roof diaphragm, and per above conversations you will not get them to design for this. I think if you are only dealing with 200lbs I would put a plywood gusset just to the right of the heel with 3-5 12d in the top and bottom and call it a day.