The domical vaults and their ribs in St Giles, Edinburgh

The relationship of the ribs to the shells they frame is key in the understanding of the balance between design and construction in Gothic vaults. A 3D survey is the ultimate method as it allows the geometries and their joints and variations to be studied accurately. This relationship can be explored in more detail in cases where the design varied across several bays of the same church, including types where ribs and shells followed different portions of a circle. The vaults in the 15th century choir of St. Giles High Church in Edinburgh show three geometric schemes, domical vaults on the Lady Aisle and Choir of Youth (before 1419) and tierceron and ribbed cross-vaults (1463-67). The former are surveyed first in this work as they are barrel vaults made to look as cross vaults with the addition of ribs, a peculiar geometry for an advanced period, but with examples in Scotland (St. Andrews, Melrose Abbey).
This work investigates their construction process, recording the webs and the full cross section of the ribs. The study will show if the ribs follow an independent traditional layout (generated as segments of circles) and how far they were simply added or functioned as framing for the webs, built in squared rubble courses. The survey was carried out with a total station, which may record less points compared to laser scanning, but is essentially treated as an analytical tool to allow key points to be selected while observing the vault up close.