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