The nave elevation is composed of three levels: grand arcade, triforium and clerestory, each marked by a cornice. The three story elevation of St. Lazare was made possible by the use of pointed arches for the nave. Each nave bay is separated at the vault by a transverse rib. Each transept projects to the width of two nave bays and the west entrance has a narthex which screens the main portal. The triforium base is decorated with a frieze of rosettes and consists of three blind arches.