The Stone Foundation is the third unlockable foundation. It has the same health as the Wooden Foundation but is more sturdy and takes less damage from most sources. A foundation is required to build any kind of housing/storage structure.
A Stone Foundation can be placed on even or slightly uneven ground. Once the first Stone Foundation is placed, subsequent Stone Foundations can snap into place along the first one, allowing them to line up, provided that there is adequate room and ground to do so.
A foundation provides the structural support to allow the placement of walls, ceilings, and other such objects, but only when the foundation is directly underneath them. It also supports up to two ceilings in any direction on the x and y-axis, and up to 1 ceiling diagonally. However, the ceilings on the far end will not support walls.