Stored it outside for years unprotected. You lose a lot more than u realize. Decided to try something different. Went with tarps. Lost some on bottom and very little on top to moisture/mold. Significant decrease in rotten hay lying on ground compared to no cover. I had to be very economical about the tie down so I used whatever was laying around( I'm sure no one else has junk laying around the farm). Went with old tires and concrete blocks(cinder blocks). Now use both on bottom, but use blocks to anchor tarp. This also allows me to peel back tarp like a banana without having to remove and reanchor. Tarp stays secure and next roles are easy to access. Tarps are difficult to manage alone(do-able but difficult). Blocks will freeze to ground but easy to move with a bump from FEL, tires no problem. A lot less hay lost I must say, and with good care, tarps finished 6th year and will be used a 7th. Fortunately I have some barn storage, and tarped hay is always fed out first. 250 rolls per year very few squares. Would like to try a tarp barn, but my experience with way I try to cram every bit in to pole barn says I'd probably have a hole in tarp barn real soon. Those who store inside know what I'm talking about. Bought biggest tarp available at that time without going for a custom make and now store 50-60 rolls under each. Can't remember exact size, probably around 30x60.