Why does stone vaulting become popular

In a self-supporting vault, the starting arches have to be built with scaffolding, but after that, the bricks or stone blocks interlock, permitting additions until the vault is complete. One of the easy ways to start an arch or construct a vault uses a "jointure", a beam or clamp with faces to grip the top blocks. Each time a block is added, the jointure is walked up to the next block on that side. The construction of jointures used to be a trade secret of masons. Some classic vaults are made to be constructed with jointures.

There are several inexpensive ways to construct concrete vaults. One of the simplest invented by Paolo Soleri is to form or dig a mold in the earth, pour the concrete, and then remove the earth. This is extremely effective with unskilled labor, and produces beautiful, durable buildings. Another way invented by Christopher Alexander is to construct hollow pillars and an inner vault surface of flimsy, good-looking surfacing materials pretty wood paneling or gypsum board.

The wooden roofs were relatively light and require no further supports. There will be, of course, considerable smoke and water damage and it will take years and decades to restore the roof.

Read more of our coverage on the fire of Notre Dame here. Cathedral of Notre Dame. The wedge-shaped blocks, called voussoirs, hold each other firmly in place and prevent each other from slipping. The voussoirs at the top, or crown , of the arch convert the downward pressure into lateral sideways pressure, or thrust , which is transmitted from the upper voussoirs down around the opening and finally into the ground through the wall or pier on which the arch rests.

Not only can considerable distances be spanned in this way, but arches can carry a much heavier load than a horizontal lintel. The arch is, however, not without its peculiar weakness. The lateral thrust is strongest at the haunches of the arch the part midways between the crown and the springing. The keystone , and the other voussoirs at the crown, press out against the voussoirs at the haunches, which may buckle and allow the crown to fall if they are not properly buttressed.

The lateral thrust at the haunches can be counteracted by the thrust of arches placed to either side, as in an arcade , but, unless the arcade is circular, the lateral thrust of the arches at the end must finally be counteracted by the sheer mass of an abutment. Since an arch depends on the interdependence of its parts, it will not stand until each of its parts is in place.