Which frame type is least likely to be used for concealed spaces or plenum areas?

In the context of concealed spaces or plenum areas, wood frame construction is least likely to be used due to several key factors. Wood, while a traditional building material, has limitations in terms of fire resistance and structural integrity when it comes to concealed or plenum spaces. These areas are typically subject to stringent building codes regarding fire safety and air quality, which often mandate materials that can withstand higher temperatures and resist combustion.

Wood can be susceptible to deterioration over time due to moisture or pest infestations and may not provide the necessary durability for installations that house mechanical systems or HVAC components. In contrast, other materials such as steel, concrete, and open web steel joists (OWSJ) offer better fire resistance and structural strength, making them more suitable for high-performance applications like plenum spaces where safety and longevity are critical considerations.

Therefore, the preference for materials that deliver enhanced safety and structural performance means that wood framing is not commonly selected for these specialized applications.