Ceiling joist overlap resists gable roof outward push, overlap how much?

I'm in the design stages of a small addition. The addition will have a 6 in 12 pitch Gable roof with a horizontal span between supports of 13 foot 7 inches. Rafters will be 2x8's and ceiling joists will be 2x10's. Is there a standard minimum overlap for the ceiling joists so that when nailed together they will safely resist the forces of the roof rafters?
Thank you for any help.
Andy Everett
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andy everett wrote:

Those are some big ass ceiling joists. What are you planning on putting up there?
Go to the Canadian Wood Council's web site - they have an online design tool called SpanCalc that lets you choose the load, spacing and species and gives you the maximum span for a given size joist.
I'm not sure if I understand your overlap question. If the span is 13'7" why aren't you going with a full length ceiling joist?
R
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I think you're looking for the wrong information... what you actually want is the nailing schedule for attaching joists to rafters.. Once you know how many nails how far apart, the amount of overlap will follow automatically.
Splice the URL below back together, or just search on "nailing schedule". http://www.co.thurston.wa.us/permitting/docs/Building_Code/Fig%2033%20fasteners.pdf
You will find that IT says that the joist-to-rafter connection requires 3 10-penny nails.
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