In ordinary construction, exterior walls are typically made of what type of materials?

The correct answer is that in ordinary construction, exterior walls are typically made of noncombustible or limited-combustible materials. This classification refers to materials that do not ignite easily and do not contribute significantly to the spread of fire. Ordinary construction, which is a common type in residential and light commercial buildings, often includes materials such as concrete, masonry, and steel. These materials provide structural integrity and help to contain fires, making them a critical component in fire prevention and safety.

While wood and siding, gypsum board, and brick and mortar are also used in various constructions, they do not consistently qualify as either noncombustible or limited-combustible materials across all situations. Wood, for example, is combustible and can readily fuel a fire. Gypsum board is often used for its fire-resistant properties as an interior material but does not typically serve as an exterior wall material on its own. Brick and mortar have noncombustible properties, but they fall under a more specific category, often termed as masonry, which may not encompass all exterior wall materials in ordinary construction. Therefore, noncombustible or limited-combustible materials are the most appropriate classification for typical exterior walls in this context.