Even the facade remained unfinished because they couldn't agree on how to finish it. The roof of the nave and apse were completed only in 1663.

Even while unfinished, the Basilica of San Petronio is a monumental church with a footprint 66 meters across and length twice as long. Its vault reaches 50 meters high. It is the tenth-largest church in the world by volume, and the largest church built of bricks.