Rood Truss Pitch Breaks (Wood)

[dcarr82775]

With pre-engineered wood roof trusses I have always tried to keep the number of pitch breaks in the top chord to a minimum (top 2 profiles in the attached) and use some overbuild where needed. I am having trouble doing this with an architect's latest creation of jogs and steps in the roof. For those of you that do truss layout on a more regular basis, how feasible is the bottom profile in the attached that has additional pitch breaks in the top chord? Of course each consecutive truss would be a little different to make up the various valleys. Thanks.

 

[woodman88]

I have done all three profiles. In practice I try to keep the over-framing to a minimum while attempting to make the roof framing for the Truss Fab. and Contractor as simple as possible. It rarely work out that way.

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.

 

[dcarr82775]

Thanks Woodman88

 

[KootK]

There is one important caveat to consider here from a diaphragm.

M. Z

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[KootK]

Huh. Sorry about the last post. It went up before I was ready to commit.

Question for you Woodman: with unblocked diaphragms, is it necessary to have blocking at the sheathing pitch breaks? I find it confusing because I've never fully understood the mechanism by which unblocked diaphragms resist shear. You know, other than testing...

My concern is that, if blocking is required at the pitch breaks and the trusses are made very complex, the framers may need special direction to ensure that blocking gets where it needs to be. With an overbuild situation, the sheathing can run continuously over the more simply profiled trusses below.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.

 

[woodman88]

Depends on the required shear of the diaphragm at the pitch break. Typically I have required the blocking along hips and valleys lines.

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.

 

[MileyDiley]

I could dig some and probably find some trusses in for custom homes that have two step downs like that due to the roof having like 12 independent hips. Architects!