Using a Wood Beam to Raise Plate Height

[reviest54]

I have seen other engineers use a 3.5x11.875 PSL or something similar on top of an existing top plate all around a home to raise the ceiling height. This feels to me like it is inducing a hinge, but I can't quite rationalize that. It seems you could almost consider it a triple top plate where one top plate is quite deep.

Any thoughts?

 

[jayrod12]

Definitely a hinge in my eyes.

I'm assuming you've seen this in retrofit applications to avoid having to reframe the walls?

 

[KootK]

X2. Hinge. Especially with the sheathing being discontinuous across the joint.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[reviest54]

Yeah in retrofit applications. The sheathing being discontinuous definitely makes a lot of sense.

thanks.

 

[KootK]

If you're getting new roof trusses, and those trusses could have raised heels, you might be able to extend the end verticals below the truss bottom chords to make up the elevation change. Keep an eye on your lateral load paths though.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[reviest54]

Thanks KootK. I was just curious after seeing it come across our plan check desk a couple times.

 

[8thStreet]

I have done this detail a few times. It is a hinge but the forces are manageable. The bending moment is low because it is near the top of the wall and can be resolved with light gauge tension straps over the discontinuous sheathing and on the inside face. The shear force is low and can be taken by toe nails into the top plate. I haven't had a problem with this detail on few different retrofits. I have looked into the raised heel for the trusses, but I haven't got anny truss manufacturer to work it out.