Arnolfo’s project was considerably different from the present structure of the church, as we can see from the exterior. On the north and south sides of the edifice, we indeed note that the first four windows are shorter, narrower, and closer to one another than the ones facing east which instead correspond to the enlargement done by Francesco Talenti, master builder as of the mid 1300s.
Arnolfo managed to finish two bays and half of the new façade. His works of sculpture were removed and transferred to the Museo dell’Opera del Duomo in 1586 when Grand Duke Francesco I de’ Medici decided to build a new façade.

At the death of Arnolfo (around 1310), work suffered a lull, receiving new vigor only in 1331 when the Wool Merchants’ Guild assumed the care of the construction. Giotto was appointed master builder of the Opera in 1334, and mainly occupied himself with the bell tower, dying three years later. Andrea Pisano succeeded him up until 1348, the year of the terrible plague that decimated the population of the city, reducing it from 90,000 to 45,000 inhabitants.
Work continued with interruptions and resumptions until after the competition announced in 1367, with the acceptance of the definitive model of the church proposed by four architects and four painters, including Andrea di Bonaiuto, Benci and Andrea di Cione, Taddeo Gaddi and Neri di Fioravante.
From 1349 until 1359, Francesco Talenti directed works, completing the Campanile and preparing a new project, assisted by Giovanni di Lapo Ghini (from 1360 until 1369). In 1378, the vault of the nave was completed, and in 1380 the aisles. Between 1380 and 1421, the tribunes were built and perhaps also the cupola drum.