Truss Plans New Construction

FYI - Anyone doing new construction phase inspections, I have come across more than one contractor that did not fully read or understand the detail truss plans submitted by the truss manufacturer. I have included a sample copy of one girder truss (2nd photo) and a generic how to read truss plans from a truss manufacturer. (attached pdf)

Look at the data labeled REACTIONS. Here you will see each truss support listed with one or more of the following: Max Horizontal, Max Uplift, Max Gravity.

Large trusses, especially girder trusses can have large uplift forces due to wind loads that far exceed the capacity of the simple hurricane clips most contractors and inspectors are familiar with. Also some trusses are design with interior wall supports, therefore do not assume all trusses are supported on exterior walls alone. Some trusses also have large gravity loads that require multiple studs to support the ends or at interior support walls.

The current house I am doing construction phase inspections on (1st photo) has several truss tie down mistakes when I arrived. In this photo the solid red circles indicate uplift loads that exceed the standard hurricane clip capacity. The numbers indicate wind uplift forces. That left girder truss has 2240 lbs uplift at the interior support wall. Notice all but five dots or circles are location on interior walls where uplift forces require a tie down bracket. Also some of these same interior support walls also needed additional studs to support the large gravity loads.

One final comment, truss manufactures DO NOT typically design the truss tie down connection. That responsibility is left to the house designer or in most cases the contractor. That responsibility also includes ensuring the truss loads, uplift and gravity, are transferred to the foundation. That girder truss with the 2240 lbs uplift required a steel rod to tie the truss down to the foundation wall. It goes without saying the contractor was not happy and gave me the standard reply “I never had to do this before!”

Good info, Randy…and nice catch.

Contractor is not responsible for appropriate design hangers for uplift and or design gravity loads supports in this state Randy.

All hangers are part of the truss manufacturers responsibility upon design values given to them by the Structural Engineer for the particular project.

Now obviously, if you should encounter H-2.5 clips in the field on a girder truss, that would certainly raise a red flag for me.
That would mean, the Contractor was not able to read the documents properly to install the right hangers required by the drawings.

Good catch.

Excellent information Randy, thanks!

Very Good Info Randy as always ! Thanx !

Indeed Thank you!