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Attic trusses

Attic trusses

Attic trusses

(OP)
Wondering if anyone has a rule of thumb for the size of rooms within attic/storage trusses. Basically looking to be able to give a customer a fairly close ballpark of how wide a room they can have in the truss. I realize that this is dependent on loads. Maybe a simple calculator out there somewhere based on spans and loading.

RE: Attic trusses

Call a truss mfg. They can tell you exaclty - No real rule of thunb but somewhere in the 50% range is not uncommon.

RE: Attic trusses

(OP)
Thanks for the reply Mike.

The manufacturers that we utilize are always willing to help out with info pertaining to the trusses. Problem is that it can take a few days depending on their workload. as you may know, people (sales dept.) need everything yesterday! We'll stick to the 50% for now as we've noticed that trend as well, making sure they know it's +/-.

Thanks again,
Doug

RE: Attic trusses

I've used a couple different attic trusses in my designs and both were 50% of the span. Also the pitch of the roof should have something to do with it. Both pitches were 12/12. One can probably get away with a slightly larger room than 50% but if you don't want sagging bouncy attic floors then its better to be on the conservative side.

RE: Attic trusses

Sorry I was trying to post this image to give you a better idea.

RE: Attic trusses

medeek, three things about which I am curious: 1) the bottom chord splice seems to be placed at maximum tension (from truss action) and bending (from floor loads.) (I have seen such splices fail, yet see it frequently), 2) it is not really acting like a pure truss, since the panel points do not coincide on the upper corners of the opening. Not to say it doesn't work, only that it might be relatively inefficient for the loading, 3) a mid-chord splice on the rafter chord, from 2x6 to 2x8 seems like an interesting choice.

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