Drywall

Sheet rock is a common building material. It is composed of two thick paper sides with a slab of compressed gypsum between them. Sheet rock is used as wall and ceiling construction material and typically nailed to 2x4 wood or metal studs, set on 16 inch centers. Sheet rock is not weight bearing and is not suitable for floors. However it can add sheer strength to a structure.

Sheet rock is also known as "dry wall" because it cannot stand up to water. When a leaky roof drips water onto sheet rock the gypsum can dissolve away and leave just a layer of painted paper in its place. A more water resistant form has a water repellent coating on one of the paper sides. The coating is green and this is called green board. Green board is a cheap solution to backing tile in a bathroom. In a heavily watered area, such as a shower, it is recommended to use cement board instead.

Sheet rock can also have a layer of aluminum foil on one side. This layer offers even more fire resistance and is often used in condominium construction. The foil layer severely limits the transmission of radio waves, such as Wi-Fi signals.

Sheet rock is typically available as 8-foot by 4-foot sheets and comes in various thicknesses, most common being 1/4 inch, 3/8 inch, and 1/2 inch.