Girder Truss location

[JStructsteel]

Got a roof with a overhang of 6'-10". For the girder truss, how far back would you have it, at least the same as the overhang? I dont want it where its a constant uplift on the GT.
Thanks

 

[JStructsteel]

To follow up, here is a sketch. Also questioning the support of the jack trusses at the end. Is there a better way to frame this, so the end jack trusses are not just hanging out there, or specify some sort of fascia beam to support them?

 

[KootK]

1) I'd push the girder back as far as you can to keep the uplift in check.

2) Truss designers have been known to employ a strategy known as "structural fascia" in these situations. As you can imagine, that scheme can only be relied upon for a modest amount of load carrying capacity. And it's a bit sketchy to have your fascia board an important structural element. But, alas, that's what is often done.

 

[dik]

In these environs, the girder truss is typically located 8' back and parallel to the exterior wall.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[KootK]

In these environs, the girder truss is typically located 8' back and parallel to the exterior wall.

I agree for your conventional, 2' overhang. At about 7', however, this case is not so conventional.

 

[JStructsteel]

Thanks, I could push the GT back over the column as shown. Perhaps I should send over to the truss types to see what they think. I agree with the structural fascia being sketchy, would you leave that up to the truss types, or something I should specify?

 

[KootK]

I'd go with a hybrid approach: ball park the fasia yourself and then, if you think that it's got legs, delegate it. No point wasting everybody's time if it's hopeless. They're goofy things to try to design in that their supports are a bunch or truss overhangs that present like springs.

 

[jdgengineer]

We employ structural "subfascias" frequently. Essentially we put in a 2x (or larger if needed) inside of the fascia. This way you are not relying on the fascia board to do the work. The fascia material is often 1x and can be a variety of materials, and the typical contractor may not be paying attention to the splice locations of it thinking it is a non-structural element.

The span of that subfascia is going to be fairly significant though. You will likely need a closed flat soffit, instead so you can support the overhang with a truss rather than a cantilevered top chord.