Do you have installation instructions on how to create a turret with Espana tile?
Interlocking roof tiles are not ideally suited for installation of turrets but there are ways to do it if enough time and preparation are applied. There is no precise formula for turret application but the attached document should give you a basic idea on how to proceed. As far as material usage, you will definitely need more tile since the coverage of each tile will be diminished by the increased sidelaps and cut work. You should anticipate that you will need 2-3 times the amount of tile that would normally be required for this size roof area.
