I am in need of information concerning wall coverings and their perspective fire ratings. Case in Point: It is mandated that I install a wall and ceiling covering which is rated at a 2 hour fire retardent rating. To accomplish this with drywall, it is therefore necessary to install 4 layers of 5/8" - 2 1/2" total. Is there a site somewhere that lists building materials and their perspective fire ratings? Thank You for your help.