Non-combustible reinforced cementitious lightweight panels and metal frame system for roofing

A method for providing a 2-hour fire resistance rating under ASTM E-119, effective 2003 to a building structure comprising providing the building with a roofing system by making the roofing system as a roof of the building structure, said roofing system comprising:

• a sloped or flat shear diaphragm supported on light gauge cold rolled metal framing of the building structure,
• the shear diaphragm comprising a reinforced, lightweight, dimensionally stable cementitious panel and the framing comprising metal roofing elements;
• the cementitious panel having a density of 65 to 90 pounds per cubic foot and capable of resisting shear loads when fastened to the framing and comprising a continuous phase resulting from the curing of an aqueous mixture comprising, on a dry basis,
• 49 to 68 weight % blend of reactive powders,
• 23 to 36.1 weight % uniformly distributed lightweight filler particles, and
• 5 to 20 weight % alkali-resistant glass fibers, and
• optional superplasticizer,
• the continuous phase being uniformly reinforced with the alkali-resistant glass fibers, and
• the lightweight filler particles comprising uniformly distributed ceramic microspheres, the lightweight filler particles having a particle specific gravity of from 0.02 to 1.00 and an average particle size of about 10 to 500 microns (micrometers),
• wherein the blend of reactive powders comprises:
• 45 to 75 wt. % calcium sulfate alpha hemihydrate,
• 20 to 40 wt. % Portland cement,
• 0.2 to 3.5 wt. % lime, and
• 5 to 25 wt. % of an active pozzolan comprising silica fume;
• and
• said making of the roofing system comprising:
• placing the cementitious panel on said metal roofing elements and
• attaching the cementitious panel to the metal roofing elements by screws with winged driller located above the point and below the threads of the screw and protrude laterally from a shaft of the screw,
• attaching a layer of Type X fire rated gypsum wallboard attached to a side of the frame opposed to said shear diaphragm to form a second diaphragm,
• wherein the roofing system meets the performance of the 2 hour fire resistance test rating under ASTM E-119, effective 2003,
• wherein Type X fire rated gypsum wallboard is only on the one side of the frame opposed to the shear diaphragm,
• the cementitious panel being above the metal framing and the Type X wallboard being below the framing;
• wherein the system has a horizontal design shear capacity of the roof shear diaphragm of 300 to 1000 pounds per linear foot.