the timbrel vault

Rafael Guastavino's patent application for the centuries old timbrel vault. ca 1880

This wide, flat vault relies on thin layers of brick, tile or stone with carefully misaligned joints, that make a laminated shell. The layers are mortared and so all the edges are held in place not by the gravitational pressure exerted on each chamfered brick or tile face running parallel to the direction of the vault, but by laminated continuous lightweight surfaces — cohesive construction, called so by Rafael Guastavino who imported the technique to the United States from the northern Mediterranean where it was ubiquitous — the Catalan vault, for example.
All this is from a dandy set of photos and texts from Low-Tech magazine

What is quite interesting is the absence of formwork, other than some regulating lines at the base of the vault.  Masons stood on the finished portions of the vault itself as the next section cantilevered ahead.  And all layers were laid down at the same time.  It is an incredibly elegant construction system, and was what Dieste used in his extended cantilevered ribbon-like vaults.

The timbrel vault in construction