The construction of this vault aimed various things:
•    Use the window frame as a formwork at the beginning of the work, so as to save a shuttering. This was the opportunity to find a way to build on a formwork which was narrower than the block thickness, which means on an inadequate support.
•    Find ways to build a bull eye and a lunette without any formworks.
•    Create openings at the apex of the vault, so as to get sky lights.

Catenary vault under construction Catenary vault for the training centre of the Earth Institute

This vault has been built in 1999 with the free spanning technique (with vertical courses) and it welcomes the kitchen of the trainees at the Earth Institute. It has been built in about 3 weeks with 4 masons and presents these features: •    6 m span, 3 m rise, 4.5 m long, 14 to 7 cm thick •    Bull eye of 70 cm diameter, catenary lunette     of 104 cm span and 211 cm rise •    Sky light done in 2 different ways •    Stabilised earth waterproofing

Starting the vault on the window frame as a centring	Starting with steps	Steps to give a lateral inertia to the arches of the vault
Sticking a block near the apex	Removing the window frame, when the vault is wide enough on top	Vault under progress
Starting the bull eye	Laying keys of the bull eye to link it with the vault	Blocks corbelling for the bull eye
Blocks corbelling further for the bull eye	Laying the keystone with 3 blocks stuck together	Building the bull eye by stepped courses
Closing the bull eye	Completed bull eye in 3 days	Keys of the bull eye
Plotting on a board the catenary for the lunette	Starting the lunette with blocks corbelling	Laying a block of the vault on the key of the lunette
Building the lunette with corbelling courses	Horizontal key of the lunette	Key of the lunette with an angle
Keys of the lunette, to be loaded by the vault	Laying the keystone	Building the lunette with radial courses and by step
Building the lunette by step	Lunette completed in 3 days	Lunette from inside with keys to link it to the vault
Raw construction of the catenary vault completed		Kitchen of the training centre