Top Plate & Trusses 1

[SperlingPE]

I have a situation where the truss does not coincide with a stud. The truss bears midway between two studs. There is a double top plate. The wood species is SPF no. 2 or btr. The additional stud interferes with insulation. Is there any way that this works? Can the load be assumed to transfer into the plywood sheathing (sheathing will be present prior to truss erection) to account for some extra capacity?

 

[TTK]

What is the application? Is this a lightly loaded residential roof truss or a heavy commercial truss?

What is the truss spacing and stud spacing?

Residential trusses at 24" o.c. don't always line up with studs at 16" o.c., and that's what the double top plate is for.

I'm guessing this must be a heavy truss application or I must be missing something with the original post?

 

[SperlingPE]

two story commercial building, roof trusses at 24" o.c., studs at 16" o.c.
I know that is what the double top plate is for. I ran the numbers for SPF no.2 or btr as the top plate and some typical reactions from the trusses.

 

[SlideRuleEra]

Are you using the NDS 2001 base design value for allowable shear of 135 psi for SPF #2? Until that edition of NDS allowable was 70 psi.

http://www.SlideRuleEra.net

 

[boo1]

In residential and light commercial wood structures, typically the combined wall section (double top plate and sheathing) support the single truss loads . If the loading is high (dead load or uplift) or when double or triple girders are used we install studs directly under the trusses. This allow for a direct load path to ground and uplift connections, and concentric loading. If you add additional members start with the number of studs to match the number of truss members, then check the systems capacity. The insulation can be trimmed to fit in the wall cavity.

 

[mrengineer]

Check out thread 507-18966.

 

[Loui1]

Is there any way that this works? Yes, the double top plate can span across 16". Even though you're bending the members in the weak axis, most of the time it works unless you have an extrememly large span, or a truss girder....at which point you should have made the contractor place a stud beneath every truss bearing location.

I personally wouldnt rely on the sheathing to provide support since the sheathing is only on one side.

If you're worrying about the top plate span, how about the single bottom plate span across the floor joists? Did you check that or provide blocking between joists?

 

[BradPL]

If you're concerned about weak-axis bending of the double top plates between the studs why not add a segment of dimension lumber strong-axis below the top plates? This can act as a T-section if you will and bridge to the nearest studs to transfer the vertical load. It won't interfere with insulation the way another stud would.

 

[boo1]

Watch for the uplift too. I like adding the studs and straps per load requirement