You get what you pay for, unless you shop at the inflated price stores.
I use the silver and black tarps, which usually last two years in hard weather and sunshine. This tarp may get ice and water drainage, in low spots, which will shorten it’s life. The tarp is tied and weighted down on all sides, to reduce any flapping in the wind, HOPEFULLY allow good drainage when snow melts. I have it over the sawdust bunker. We have angled boards under, like roof trusses to give drainage to the snow and rain on top.
You can pay big price, small bargin price, the silver and black tarp lasts about 2 years at our house. I do take the split pieces, sometimes can tape them up for another few months, or make new, smaller tarps with added grommets on the ripped side.
Canvas tarps are really expensive, not that waterproof. Do last fairly well over a few years, unless not tied down well. They flap and shred just like the cheap ones in a big wind.
I do not find ANY tarp to be truly waterproof, if it is touching the hay or sawdust. Water will wick thru from collection pressure above (bubble down) or contact by touching bales it lays on. Those who layed sheet plastic on bales, under the tarps, got mold under the plastic. You can’t seem to win with outside storage of hay.
So maybe one of the metal frames, with tarp above, not touching hay, would be a better storage idea. Yes, you still will have to replace the big tarp every couple years, but maybe hay would keep better with no physical contact with the tarp itself. Those frames with tarp over do seem to stay anchored pretty well, not usually flapping in the wind. You could add secondary tarps to close one end and the sides for added weather protection.
Sorry about your hay.
