Red Seal Lather (Interior Systems Mechanic) Practice Exam

What is the most common thickness of drywall used for ceilings?

1. 1/2 inch

2. 3/4 inch

3. 5/8 inch

4. 1 inch

The correct answer is: 5/8 inch

The most common thickness of drywall used for ceilings is 5/8 inch. This thickness is preferred because it is denser and more robust than thinner options, which helps to reduce sagging over time, especially in larger ceiling spans. The added weight of the thicker board also helps to improve soundproofing and fire resistance, which are critical factors for ceilings in many building codes. By using 5/8 inch drywall, contractors ensure that the ceiling will not only maintain its structural integrity but also provide an effective barrier to sound and fire, making it the ideal choice for residential and commercial applications. In contrast, options like 1/2 inch drywall, while often used for walls, may not provide sufficient support for ceilings, especially in areas with heavier loads or expansive designs. Similarly, the other thickness options, such as 3/4 inch or 1 inch, are generally not standard for ceilings due to their heavier weight and impracticality for typical residential or commercial ceiling applications.