Canadian Codes permit design for a stipulated occupant load, i.e. max posted limit. A class room load of 50 psf would be reasonable as long as an assembly occupant load of greater than 60 persons is not reached with in the floor space. At that point you would need to consider assembly loading...
I would suggest starting with the local building dept. If you deviate from Part 9 of the National Code you will require a designed foundation by a P. Eng.
Part 9 will require a concrete footing below frost unless the soils are non frost susceptible. Concrete piers or masonry pier blocks on...
Generally when I get to the 35k range or higher I start to look at using continuous tie rods, pier to pier. Rods threaded and connected with threaded couplers etc, or continuous rebar sized for the tension load pier to pier.
You seam to be at your limits for 20m hairpins especially if there...
Also consider sliding snow from a high roof such as a Pre Eng structure. Generally we provide extra wall girts at the base for the horizontal load that would other wise buckle the light weight sheeting.
Moderately surprised that the local building dept could not answer your question. When you call a building dept. in a Canadian Prov make sure you are talking to a C.B.O., ( chief building official).
Perhaps you got the floor sweeper. I agree they should have been able to respond to your...
