The nave was built in stages. The oldest part likely dates from 1355 and consists of a one-naved, cross-shaped building with today's fourth bay as the crossing and today's crossing as the choir, as well as the second and third bays and the fourth bay's side nave. The tower stood on the spot where today the first bay stands. In the fourth bay's north side nave is found a fresco-secco painting from the 14th century. Bit by bit, the bays were widened with side naves. The nave was likely only joined to the tower after that was finished.