There's a collision issue that prevents the player from walking under it. This is the same for any similar form of the Lumber wall: Lumber Doorframe, Lumber Glass Wall, ect. This can be fixed by manipulating the ceiling height with pillars.
There are (4) different variations of Lumber Wall in-game:
1. A pale shoddy design that can be spawned in by gfi command
2. While in-game, if you cancel placement then position the green placement icon again a couple times, you may get W-frame wall, [X]-[X]wall, or the usual plain Lumber Wall
The Lumber Wall is treated as a wooden structure and can not be damaged by hands, stone weapons, or non-explosive ranged attacks.
The following aggressive creatures can not damage the Lumber Wall: