'15 IRC Table 507.6, deck beams

[Sifu]

I have puzzled over this before and now that it is in code (something for which I am grateful) I want to hear some other input.

Footnote b. "Beams supporting deck joists to one side only". I understand the restriction if hung on one side of a built up beam, but does this also indicate that you could not use these spans for a drop girder?? And if you had a flush beam with joist hung on both sides how would the beam spans apply?

 

[JBI]

Read the text of Section R507.6 in order to understand the application of the Table. The table applies to beams "... s shown in Figure R507.6.."

 

[Sifu]

I guess I am dense, I still don't understand how the footnote applies. If I have a dropped girder under a deck supporting joists from both sides can I not use this table? FWIW the I believe the DCA deck manual contains the same statement. Seems to me the beam could still be sized for the spans combined from both directions. Like I said if it were a flush beam with the joists attached to the face member of the beam from both sides I can see how there might be limitations on the individual face members.