How to tie rafters to floor truss

[carlsonNY]

Hey guys,

I am hung up on this one. I am designing a 28' wide building, 1 1/2 stories. I want to use floor trusses for the attic floor and a roof using 2x12 rafters with ridgeboard. I am having a hard time figuring out how/if I can tie my rafters to the floor trusses to prevent outward thrust.

Any ideas? Thanks!

C

[akwoodchuck]

Simpson Strong-Tie VPA?....
https://www.strongtie.com/raftertowallconnectors_solidsawnlumberconnectors/vpa_connect/p/vpa#CodeReports&Compliance

[carlsonNY]

That looks good to me, thanks woodchuck!

[Don_P]

Let's think about that more. You are needing a continuous tie across the rafter feet. The floor truss manufacturer needs to be aware of that so he can design his splices accordingly. Hopefully their engineer will offer some guidance although he cannot (or liability wise, will not) design the rafter to truss connection. Doing a little checking, that VPA hanger is rated for 300lbs in the direction we are talking about, it is also frowned on by many inspectors. Look at table R802.5.2, the heeljoint connection table and do a little reverse engineering, I think you are pushing that 300 lb connection mighty hard. Something like an L70 on top of the truss and alongside of a birdsmouthed rafter would give more restraint but again discuss that with the truss engineer, you would be pushing the end nailing distances on his truss. One of the twisted straps might get you further from the end with the nailing. Correctly you are in an engineer required spot.

Another path that does provide the engineering is if you can tolerate an attic truss. The floor system is part of the truss and is smaller members since the floor and roof as a system are working as one unit, it is a truss of great depth compared to a floor truss alone. The downside is the loss of the kneewall area. The upside is that connection is engineered and the speed of assembly (small crane required though). If you explore that have them cantilever the truss, launching the top chords from the overhang rather than the wall, this will give more interior space.

[WISteven]

Use a ridge BEAM so you don't need to worry about the outward thrust.