box beam design

huangyhg

box beam design
i am building a 28' x 48' loft - metal roofing 5/12 slope, partitioned in the center making two 28' x 24' rooms.  i want to span the entire 24' and support the loft floor.  i would like to keep the box beam depth at 10".  i was thinking 2x6 frame (like a standard wall 16"oc with doubled top and bottom plates) with 1/2 or 3/4" plywood on either side.
does anyone have experience with this type of design/construction?  can you give me some idea if this is close or what would i need to carry the loft / sleeping rooms (24' x 14')?
thanks for any 'constructive' feedback.
mark