Arches and Vaults in Architecture Arch and Vault, a fundamental construction system in architecture used to span the space between walls, piers, or other supports and to create a roof or a ceiling. Until the 19th century the arch and vault were the only alternative to the far more limited and simpler post-and-lintel system supporting a flat or peaked beamed roof. Arch An arch, in construction, is a rigid span curving upward between two points of support. It appears in a variety of structures, such as an arcade, formed by a row of arches, supported by load-bearing arches or a roof or a bridge, or as a single, fr