Stereotomy is the complex geometry used to calculate the exact angles and shapes needed to cut heavy stone blocks so they fit together perfectly. It is essential for building load-bearing arches, vaults, and spiral staircases without relying on mortar for structural strength. Master masons use these principles to turn flat architectural drawings into three-dimensional templates for the stonecutters.
The stereotomy on that groin vault is going to require precise templates for every single voussoir.
While largely replaced by structural steel and concrete, true stereotomy is still required for high-end historic restoration and traditional cathedral construction.
Related terms
Workstone
A dressed block of stone prepared for laying in a masonry structure.
Ashlaring
The short vertical timber framing installed in garrets to cut off the sharp angle where the roof meets the floor.
Barrel vault
A continuous arched ceiling or roof structure that resembles a cylinder cut in half lengthwise.