Loft in pole building question.

[Daylate$short]

I am having a 42' wide, 80' deep, 16' sidewall pole building constructed. Fill dirt is being hauled in now. The poles will be put in (10' on center) and then a 5" concrete (3500 psi) floor installed. After the floor is in, the rest of the building will be completed. At some future time I would like to put a loft across the back of the building which would be 42' wide. It would be 16' deep. I have on hand enough 16' 2X12s(16" oc) and 3/4" osb to use for this. The loft would be used for storage and possibly a game area. I realize this is a engineering question, but if someone has done this before, I would appreciate their input. The building will be used for truck/trailer, boat, camper, car, tractor and bulldozer storage.
My question is, what should I do before the building is completed to allow me to add the loft. I am going to need a beam with joist hanger across the 42' width. Should it be micro lams or dimensional lumber? How many posts for support and what kind of footings under the posts? I am located in the midwest. Thanks!

 

[1320stang]

What do you plan on putting under the loft? Boats campers and cars? Will it be a work area or is the building storage only? What do you plan on putting in the loft storage wise (lbs/sqft)? Based on what you have given, I'd put five 4"x.25" steel pipe columns on 10.5' centers in (3 in the middle and 2 at the outer walls) and I might thicken the slab to 8" in a 24x24 area at the column locations. You could put J-bolts in, but I'd just drill them after and use anchor inserts. Use a 8x8x3/8 plate on the bottom and make a U shaped cap at the top to receive a double 2x12 beam.

 

[Daylate$short]

The building will be used for storage. I am planning on 8' from the slab to the bottom of the joist for the loft. That will allow cars, small tractors, snowmobiles, lawn equipment etc. in the low clearance area. As for lbs/sf in the loft, I am not sure. It will be storage of off season items, camping gear, Christmas decorations(don't ask) basicly anything that is too good to throw away that I am able to carry up the steps.
Thanks again for your comments!

 

[1320stang]

I think what I put down in my previous post will suffice. It gives you 10.5' wide bays which would allow a open car hauler between columns. Be wary, paper (old boxes of taxes) can weight quite a bit. Of all buildings, Libraries have the highest lb/sqft capacities. Even Office buildings have a higher capacity than parking garages, that's why you sometimes see old office buildings converted to parking garages.