Geographic and chronological extent of brick vaults by slices

Vaults are built with vertical or slightly pitched bricks, in which each ring, arch or course forms a slice leaning against the one before, in such a way that no formwork is needed. Mud or lime mortars have commonly been used. Quick-drying gypsum mortar, used mainly in the Muslim world and in Al-Andalus, implies less difficulty in holding each piece together and gives rise to slightly different solutions. This technique originated in classical times and spread in the area that would later become the Eastern Roman Empire and Byzantium. Similar vaulting techniques can be found in Medieval Europe and North Africa. Many examples are known in the Iberian Peninsula dating from the 9th century onward. A particular type of this vaulting thrived in the bordering regions of Extremadura (Spain) and Alentejo (Portugal) during the early Modern Age. Following this expansion to the west, similar techniques have also been employed in Mexico up to the present day, probably introduced by Spanish builders.