Which condition is essential for adequate support of a basement wall?

Having the weight carried evenly by the sill is critical for the adequate support of a basement wall because the sill plate is the horizontal member that transfers loads from the wall down to the foundation. An uneven load distribution can lead to structural issues, such as wall bowing or cracking. When the load is properly distributed, it ensures stability and support for the entire structure above.

While other factors are important as well, they do not directly address the immediate necessity of a well-supported wall. For example, thickness of the wall or window size can contribute to overall aesthetics or energy efficiency but do not fundamentally impact the structural integrity. Similarly, while the foundation extending below the frost line helps prevent frost heave and other earth-related issues, it does not directly ensure the even load distribution necessary for basement wall stability. Hence, even load distribution is key to supporting the wall adequately.