Red Seal Lather (Interior Systems Mechanic) Practice Exam

What is the ideal spacing for ceiling joists when installing drywall?

1. 16 inches on center

2. 20 inches on center

3. 24 inches on center

4. 30 inches on center

The correct answer is: 24 inches on center

The ideal spacing for ceiling joists when installing drywall is typically 24 inches on center. This spacing allows for adequate support of the drywall panels while also facilitating the installation process. Drywall sheets are usually 48 inches wide, and spacing the joists 24 inches apart provides sufficient structural integrity to avoid sagging over time. This method also enables easy fastening and minimizes the number of joints, leading to a smoother finish when the drywall is taped and mudded. The other options may not provide optimal support or could lead to complications during the installation. For example, 16 inches on center is commonly used for wall framing to provide enhanced support but may not be necessary for ceiling applications where the loads are different. Similarly, 20 inches and 30 inches on center could lead to issues such as sagging or increased potential for cracks in the drywall, as these spacings do not align well with standard drywall dimensions and can compromise the integrity of the installation.