Cement board is commonly used as what type of material in construction?

Cement board is commonly used as underlayment in construction. Its primary function is to provide a stable, moisture-resistant surface for tile installations, particularly in areas exposed to water, such as bathrooms and kitchens. By using cement board as underlayment, it enhances the durability and longevity of the floor, reducing the risk of damage from moisture that can compromise both the flooring materials and the underlying structure.

This choice is relevant because cement board is specifically designed to withstand moisture and act as a reliable base for tiles, making it an essential component in wet areas. The other options refer to materials with different uses: insulation is aimed at thermal performance, structural support is related to load-bearing elements, and wall finish refers to decorative surfaces, none of which align with the primary function of cement board.