Diaphram/Collector Connection

[TimmyH76]

What is the proper way to get the force from a roof diaphram fastened to truss down to a masonry shear wall. I know there are several options, but here's the part I'm interested in....The truss is an atic truss. So the distance from the diaphram to the top plate is 2'. Thanks.

 

[miecz]

Why not use blocking between the trusses?

 

[CJJS]

Sometimes, with high heel conditions like you have, flat trusses are made to fit between the top plate and the diaphram, and between the trusses.

 

[TimmyH76]

Is there something made by simpson strong tie or ups for this aplication? The way i'm thinking of it diagonal (tension only) bridging going from the top of the truss to the top plate would work good. Any insight on this...Thanks.

 

[NKT]

You could add sheathing to the underside of the eaves. This effectively wraps the diaphragm around the outer edge of the roof, back to where it meets the top plate. You can also look at this as a long second-floor shearwall, laid flat. Make sure the “holdown” forces at the ends have somewhere to go (probably into the perpendicular top plates).

 

[scottiesei]

If the heels are exposed, won't they be covered in sheathing? The verticals may act as studs in a shearwall, no?!?

 

[NKT]

TimmyH76:
Can you give a more thorough description of the truss construction around the bearing wall? If we have a clear picture of what you're talking about, you might get more meaningful advice.

 

[JLNJ]

I like CJs's idea. Fab a special piece to fit in the heel which will bring the load down from the sheeting to the masonry.

For shorter heels I've used a thin bent plate. Maybe you can do it by extending the CMU wall up the 24".

 

[JLNJ]

Whatever rational method you employ, the contractor will say "I've never needed to do anything like that before in my 1000 year career!"

 

[twinnell]

We usually use plywood between every other truss. The plywood is framed by 2x's around the perimeter and the 2x's are nailed to the roof deck, trusses, and top plate. mini shear wall.

 

[UcfSE]

Take a look at Simpson's META and HETA straps. They can be doubled-up if necessary.

 

[TimmyH76]

Ok I'll try a better description:

I have a 12" reinfored CMU wall coming up to a top plate (the top plate will be used as a nailer, at the contractors request, rather than usiing masonry/wood tie downs) The truss is 24" tall at the point it meets the bearing wall. The 24 " is from the topplate to the sheathing. The trusses are 2' o.c.

I was trying to eliminate the need for the contrator to have to construct a mini shearwall between the trusses. I think what I'm going to do is run sheathing along the end of the truss (so the sheathing will be be vert oreinted) and nail to the end of the trusses, to the top plate along the bottom, and 2x4 blocking along the top between the trusses. The roof sheathing will be nailed to the 2x4 blocking at the top.

Thanks everyone for the input.

 

[scottiesei]

That sounds good. Just watch the plate and truss fastening for the shear and uplift. e=2' prob will not net much overturning.

 

[twinnell]

So there isn't an overhang? If not your idea sounds good. The mini shearwall is good for trusses with an overhang.