hey those are nice. we kind of inverted the idea of those by building a loft for the other stuff and putting fert below(along wiht mowers) we are going to store it in shipping containers later when we buy them to free up all that space that is now needed.
i am unsure though about a loft made of wood to support all that weight, depending on how many pallets you are looking to store at a time and how long the space is.
besides the obvious things like phasthound has, my dad could answer those questions 4 u as he is a building inspector, if he does not chime in, pm him here
If your going to build your own racks I would consult an engineer . Steel racks are probably your best bet and the weight ratings are available from the manufacturers. Why wouldn't you just double stack the pallets of fert anyway??? Racks will not really gain you any space.
Originally I wanted to use the space underneath for equpment that we needed frequently and our "progress boards" . I did consult with an engineer and he was talking 2 x 16" joist with12 inch centers which was way too much money. We're just going to make due. It will be a little tight but after the first cycle we'll be fine. Thanks for the input.
Racks are the best way to go. They are built for the weight, cost less than building a loft, are fast & easy to set up and break down. You can adjust the height for each section and if your ceiling is high enough you can get a system that will stack 3-4 levels high. The one pictured holds 16 pallets.