Gypsum to Steel Roof Connection

Gypsum

• Gypsum is a mineral used to create a cement-like building material. Manufacturers fashion gypsum into hard boards used to frame house walls and, in some cases, roofs. Two types of gypsum are used on roofs: prefabricated gypsum boards installed one at a time across the roof surface or gypsum decking poured in its clay-like form across the roof and allowed to harden in place. In addition to improving the fire-resistant qualities of steel roofing, gypsum can improve the insulating ability of steel to prevent heat loss in the home.

Mechanical Fastening

• Mechanical fastening is the most commonly used and accepted method of attaching gypsum boards or decking to steel roofing. This is a fancy way of describing the process of attaching one material to another with tools and screws, nails, pins or bolts. A report published by ICC Evaluation Service, a company that performs technical evaluations for code compliance, recommends using Type S screws to attach gypsum board to steel. This publication also recommends using 1 1/2-inch-long Type G screws on both sides of all end joints. The Steel Framing Alliance recommends using Number 6 screws on steel that is 1 1/3 inches or less in thickness and Number 8 screws on all other steel.

Roof Assembly

• Gypsum board and decking often appear in roof assemblies. Roof assemblies constitute all of the layers that make up a roof, from the frame to the final covering. In such instances, gypsum board or decking usually sits directly on top of the roof frame. When attaching gypsum to a steel frame, use the recommended fasteners. You must use additional layers to apply steel roofing sheets on top of gypsum board, such as a roofing membrane, metal deck panel or a roof covering. Gypsum decking requires no additional layers -- you can attach metal roofing directly to it, as per the manufacturer's instructions, with the recommended fasteners.

Adhesives

• When using gypsum board in a roof assembly, you need an adhesive to attach the roof deck or covering to the board. Some gypsum board comes with adhesive material on one side that can be activated by peeling away a strip of covering paper. Otherwise, purchase a weatherproof adhesive rated for use with gypsum and the roof decking material from a hardware or home supply store. Roof membrane is itself an adhesive. It can be applied directly to gypsum and other roofing materials and forms a protective coating that also helps bind materials, such as steel roofing, to boards. Roof membrane usually comes in a glue-like material that applies wet and hardens or as a tape.