Red Seal Drywall Finisher and Plasterer Practice Exam

What is the primary purpose of using joint compound in drywall finishing?

1. To attach drywall sheets together

2. To fill gaps and create a smooth surface

3. To prevent moisture damage

4. To provide structural support

The correct answer is: To fill gaps and create a smooth surface

The primary purpose of using joint compound, often referred to as mud, in drywall finishing is to fill gaps and create a smooth surface. Joint compound is applied over the joints and fasteners in drywall installations to blend them seamlessly into the surrounding surface, effectively concealing any imperfections. This promotes an even appearance across the wall or ceiling once it is painted. In addition to gap filling, joint compound also helps to improve the overall integrity of the drywall edges by providing a layer that can be sanded and smoothed, which is essential for achieving the professional finish typically desired in drywall work. By ensuring that all joints are filled and smoothed out, the aesthetic quality of the final product is greatly enhanced. The other options involve functions that are not the primary purpose of joint compound. While joint compound does have some insulation properties against moisture due to its density, it is not specifically designed for moisture resistance. Also, the attachment of drywall sheets relies on mechanical fasteners such as screws and nails rather than joint compound. Lastly, joint compound does not provide structural support, which is the role of the drywall and framing system itself. Its main function is strictly related to finishing, aiming to create a polished, flawless surface.