Metal is designed to be installed using special self-sealing screws. Each metal panel has a designated uplift and manufactures specify exactly how many fasteners per square foot are required. If metal panels are fastened outside the specifications the manufacturer’s warranty is voided and the roof assembly is out of code. This also leaves the roof susceptible to roof blow-off in the event of strong winds. When a new code system is introduced, the requirement has increased. Most of the good roofing contractors still install extra fasteners in order to achieve the enhanced wind resistance.