California Residential Inspector Practice Exam

When using gypsum board as a draftstopping material, what is the minimum thickness required?

1. 1/4 inch

2. 1/2 inch

3. 3/4 inch

4. 1 inch

The correct answer is: 1/2 inch

Using gypsum board as a draftstopping material is a common practice to help prevent the movement of air and to contain smoke and fire within certain areas of a building. According to building codes and standards, the minimum thickness for gypsum board used specifically for draftstopping in residential construction is 1/2 inch. This thickness is deemed adequate to provide the necessary structural integrity and fire resistance needed to mitigate the effects of smoke and fire spread through concealed spaces, such as attics and wall cavities. The 1/2 inch thickness balances structural needs while remaining manageable for installation. Thinner materials may not offer the requisite durability or fire-rated qualities necessary for effective draftstopping, and thicker options are generally not required unless specified for particular applications or circumstances where enhanced protection is necessary. Hence, the choice of 1/2 inch adheres to industry standards and practices for ensuring safety in residential environments.