As a general rule the industry standard for most barns is 12 oz material. Almost all of the companys purchuse their tarp material from one of two companies, either Intertape Polymer or Fabrene. That is why almost all buildings have the same 15 year pro-rate warranty on the tarp for manufactures defects. In most cases when a tarp is properly tensioned on a Winkler truss barn a customer should expect to get 20 to 25 years out of their tarp. Replacement cost after that time is a fraction of what it would cost to resteel a pole barn roof. Most hail will bounce off of a polymer roof unless it is really big and jagged in which case it would also bang the heck out of a steel roof also. Winkler Canvas Structures is the only company that can say that we have never had a truss come down. Period. Most of that is due to the fact that our building has on average 30% more steel than the competion. Also our structure is enginered for wind and snow loads without the cover. Other companies rely on their cover as part of their structural integrity.