How high is Wall of Stone?

[Amitay]

Hello,

One of my players wanted to use the spell Wall of Stone, to encase its enemies on a "cage". However I'm not really sure on how high the stones should be, the spell says:

"This spell creates a wall of rock that merges into adjoining rock surfaces. A wall of stone is 1 inch thick per four caster levels and composed of up to one 5-foot square per level. You can double the wall's area by halving its thickness. The wall cannot be conjured so that it occupies the same space as a creature or another object."

Should I consider 5-foot cubes? So that if she wants to build a column 10ft high, with an area of 5ft she would "spend" 2 cubes? Or I can assume that 1 square of the wall goes to the ceiling?

Thanks.

[Orfamay Quest]

From the description:

"whose area is up to one 5-ft. square/level"

The key word is area. You get a volume of 5 feet by 5 feet by 1/4 inch per level.