Red Seal Drywall Finisher and Plasterer Practice Exam

How long must joint compound typically set before sanding?

1. 12 hours

2. 24 hours

3. 48 hours

4. 6 hours

The correct answer is: 24 hours

Joint compound, also known as mud, typically requires a setting time of approximately 24 hours before sanding. This timeframe allows the compound to fully dry and cure, ensuring that it has the proper consistency for sanding. If you sand too soon, the joint compound may still be wet or insufficiently cured, leading to uneven surfaces and possible damage to the finished surface. A proper setting time is crucial in achieving a smooth and professional finish on drywall joints. When joint compound is sanded before it is adequately dry, the sandpaper can create gouges or uneven areas, making it more difficult to achieve a flawless final coating. Choosing the 24-hour setting mark as a standard aligns with best practices in drywall finishing, providing enough time for the material properties to stabilize and facilitating better sanding results.