What is the lowest member of the frame structure that rests on the foundation?

The lowest member of a frame structure that rests directly on the foundation is known as the sill. The sill serves as the base component that connects the structure to the foundation, providing a stable and level starting point for the framing. It is critical in establishing the layout of the building and transferring loads from the frame to the foundation.

In residential construction, the sill plate is typically made of treated lumber to resist moisture and decay, thereby ensuring the longevity and stability of the structure. This element is essential for achieving proper alignment and support for the vertical framing members of the walls, which are anchored to the sill. Understanding this foundational aspect is crucial in construction, as it plays a significant role in the overall structural integrity of the building.

While other terms like flange, joist, and stud relate to different members of the structure—such as horizontal framing members and vertical supports—they do not serve the same foundational role as the sill.