The roof decking could be the layer of plywood or O.S.B. nailed into the trusses or rafters. Roof decking is often 7/sixteen” and comes in four’x8’ sheets. If you’re tearing off old roofing, the roofer can try to find destruction that needs to be repaired when the deck is bare. https://johnnylsxch.wonderkingwiki.com/793322/the_2_minute_rule_for_roofers_in_joliet