I am going to build a somewhat large (25’x15’) on-grade storage building and I’m looking for some insight/recommendations on my floor framing options.  My primary focus is making sure that I’m framing out a floor that will withstand some heavy weight.  I will be using it to store attachments to my tractor (54” snow blower, front-loader bucket, 48” rotary cutter…) and a 60” zero turn mower.  It’s important to note that I’ll be riding my 1,400lb subcompact tractor in/out to drop-off/pick-up attachments, but will not be storing it in the building.

Ideally, it would be nice to frame-out the floor with doubled-up 2’x10’ rim joists and then 2’x8’ OC joists with hangers.  I don’t have experience in engineering floors, but from everything I’ve read, I don’t think this would hold-up given what I will be storing and how I will be using the space.  There are a number of different alternatives and I’ve attached a picture of (2) options that are self-explanatory.  With either of these (2) options, I would be building it on concrete blocks sitting on a gravel base under the both rim joists and beams.

I would certainly appreciate any insight/recommendations/comments on what I’ve proposed as options as well as any other options.  Thanks!