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Re: Valley Rafters

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I don't think you're missing a thing.  This is just one example of the difference between the way "we've always done it, and it's worked fine" and the "ivory tower" (i.e., engineered) approach. 

I've seen enough old roof framing -- with its many sags, splits, twists, irrational framing details, incipient failures, etc. -- to feel comfortable in following what I believe to be a rational engineering approach, such as you've done.  No cutting corners!  Here in the lowlands of California, where it doesn't snow, our roofs can stand up with practically *no* framing (2x4 rafters @ 32" oc spanning 12', for instance!), but only because they're never tested by snow, etc.

You can't "prove" that something's adequate if it's not.  And *lots* of things that have been done for eons are really not adequate, we just may not know it.  And there ARE failures, infrequent though they may be.

Stick to your guns!  (Ignorance is bliss.)

Ralph Hueston Kratz, S.E.
Richmond CA USA

In a message dated 2/7/09 7:38:39 PM, ENGRLAINES(--nospam--at) writes:
An architect client asked me to answer a building official's request to verify the strength of a valley rafter (or beam) in a wood roof. The architect specified a valley rafter 2" deeper than the rafters (as usual), but this time he is being challenged to prove it. I analyzed it as a simple beam taking half the tributary load from the jack rafters framing into it and it is in fact way off! The architect maintains that he and everyone he knows have always spec'd 2" deeper for decades with no failures or even challenges. He even showed me text books and other reference books with this recommendation. Am I missing something?
Charles O. Laines, S.E.

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