The studs are 2x4 and exposed. The intuitive thing would be to simply lag 2x6 to each of the 2x4 wall studs that are 16 on center, and cover the thing with plywood.

Using the calculator here http://www.awc.org/calculators/span/calc/timbercalcstyle.asp

It shows that I can do 2x8 at 16" oc for a span of 12' 7". This raises a few questions for me, if someone will indulge:

1. Would it be best to put up one 2x8 at 64 inches out and then use joist hangers on 2x4 or 2x6 lumber for the shorter span (64") or simply put up 2x8 for the full span?

2. Will it be sufficient to lagbolt the 2x8 to the 2x4 wall studs or will I need to add an additional jackstud under each of the 2x8 as well?

3. Would it be better to do this like an outside deck, in that I would put a 2x8 against the wall studs on both sides and span the loft area using joist hangers?

Is there another (better/easier) way I have not thought of yet?

You shouldn't need 2x8's unless the live load is greater than 20 PSF. What are you putting up there?

I am not sure what specific things will go up there. Perhaps wood, perhaps old hand tools, scrap metal, old motors, locks, books, packiaging materials, paper records. Who knows. At this point I need merely to not waste space. I have precious little enough, and having such an area not utilized would feel foolish.