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Posted by on January 14, 2007, 8:51 pm
Goedjn wrote:
> On 3 Jan 2007 22:38:47 -0800, shuffman@gmail.com wrote:
>
> >My garage has W-trusses spanning about 30 feet, the bottom edge of
> >which form the ceiling joists.
> >
> >I am interested in hanging a shelf along the width of the garage
> >(parallel to the trusses), spanning the full 30 feet. The shelf will be
> >constructed of four 3x8 sheets of 1/2" or 3/4" plywood, resting on a
> >2x4 bolted against the wall. I would like to hang the other end of the
> >shelf from one of the trusses with cables.
> >
> >In addition to the weight of the shelving unit (perhaps several hundred
> >pounds) I estimate I'll be storing about 1000 pounds on the shelf. Of
> >course some of the weight will be borne by the 2x4 bolted into studs,
> >but around half the weight will be borne by the truss.
> >
> >I have read that trusses have poor 'hanging strength'. Should I be
> >concerned about this weight being borne entirely by a single truss?
>
> Adding nearly half a ton of load to one truss will be a bad thing.
> You should find a way to post down to the floor. Failing that,
> and if this is an open truss, you should attach stringers to the
> TOP cords, spanning several trusses, and ignore the bottom chords
> entirely.
OK, I've been sufficiently dissuaded from my original course of action,
but posting to the floor will also be problematic (the shelf will be
located over a 30' long workbench, and posts would get in the way.).
The trusses are not open; I have sheetrock and insulation in the
ceiling. Would one of the options below be robust?
1) Bolt several 2x4s vertically from the truss' top chord to the bottom
chord, then fasten the cables into the bottom chord? This should
transfer the load to the top chord.
2) Same as #1, but on two trusses. Then cable the shelf to both trusses
rather than to only one.
3) Run cables from the bottom chord of the truss to the top chords of
several adjacent trusses? (It would seem like this would apply lateral
load to the adjacent trusses, so I'd run 2x4s perpendicular to the
trusses for stability)
Thanks for the helpful advice,
Sam
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