So I am building a rather large (large for me anyway) barn/sheep shelter. It will measure 16x48 when complete. I have already started the framing, as you can see in the pics (the diagonal pieces are just temporary braces). When complete this will be a single slope structure, with all the walls enclosed except for a 8 foot section on the tall side.
So I might not have made the best decision with the footings. I think they are fine, and I am not worried about their ability to hold the weight. My concern is the uplift. I'm just not terribly confident with them, or rather, my use of them. The have hard-plastic 12" "plates" screwed onto the bottoms, although I had to cut some of them. I saw on the manufacturer's site that it will support 900 lbs of uplift, I think, but I just could not get them all the way down in this soil, even spending all day with a skid steer and big rock auger. So I got what I got. I'm not changing the footings.
I know that nothing will withstand a tornado. However, I'm worried about a strong t-storm coming along and carrying the thing off to Mexico in a crumpled-up ball. My first instinct, as always, was to overbuild ... big beefy rafters, 16" o/c, roof deck, then tar paper, and finally metal.
But then I thought today ... if I have a super-stout roof, like I planned, maybe it really will get carried off, and no joke. But if I just have some thin 1x4 cross members (purlins?) across light rafters at 24" o/c, and some r-panel screwed into those ... maybe the storm will simply peel the roof off, leaving the frame, rather than bolloxing up the whole smash. I can handle that.
Am I being silly thinking this way? Do I need to go ahead and build the tank roof?