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Re: Ceiling joists/rafter ties IRC R802.3.1

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Jim,

This may seem like a cop-out, but what do the numbers say? In a prescriptive design sense, it would seem reasonable to require any horizontal thrust be resisted by a defined load path, hence the requirement. Can the load be taken out through another means? For example, is the ceiling joist below where the hip rafters meet the ridge strong enough (including connections) to support the hip rafter as a structural beam (and is the hip designed structural)? If not, can it be beefed up to support the load? If not, then I'd say the tension ties are technically necessary. Will the building fall down if you don't? Probably not soon. Since you've got a ceiling, the gwb will support some tension at the hip-jack ends, and transfer the force to the side walls via shear. It depends on whether the gwb is strong enough under a full code load and whether you are comfortable using is as a primary structural path.

Jordan

Jim Wilson wrote:

IRC R802.3.1 Ceiling Joist and rafter connections:

"Where ceiling joists are not parallel to rafters,
subflooring or metal straps attached to the ends of
the rafters shall be installed in a manner to provide
a continuous tie across the building, or rafters shall
be tied to 1-inch by 4-inch minimum-size crossties."

Does this apply to the secondary direction in a
hip-framed roof?  Some inspectors insist so, some
don't know, some don't know that they don't know.

I've never seen it applied this way in the field, but
one prominent local builder has been specifying
two-way ties on their hip-roof structures.  I would
like to either back them up, or save them the effort
and the consumer the added cost and inconvenience.

Thanks in advance.
Jim Wilson, PE
Stroudsburg, PA

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