1436. Construction began two years later, but work was soon suspended.
1444. Work is resumed in 1444.
1446. Brunelleschi died in 1446, and only the foundation and part of the outer walls had been built. He was succeeded by several builders who made changes to some parts of his design.
1471. In 1471, most of the old church and convent was destroyed by fire.
1482. The new structure was completed in 1482.
The façade was begun in the 1480s, at which point it was decided to incorporate three portals and not four. This facing was not completed until the eighteenth century, which accounts for the presence of its graceful Rococo curves.
This church is similar to San Lorenzo in many ways.
The proportions of both churches are based on modular systems in which the crossing squares are repeated for the choir and transept arms, halved for the nave bays, and quartered for the side-aisle bays.
At both churches, pendentives support the central dome, and pendentive vaults, or sail domes, cover the side-aisle bays. Had the dome of San Lorenzo been built according to Brunelleschi's design, it would probably have been similar to the dome of Santo Spirito.
Consequently, Brunelleschi was free to work out some of the problems encountered with his earlier design for San Lorenzo.
The modules on which the church's lateral proportions are based were measured from the centers of the columns, rather than from their outer edges as they were at San Lorenzo. This refinement made it possible to apply whole-number ratios to the main parts of the church without factoring in the space between modules.
The entire perimeter of the church can be traversed through a line of small connecting bays that form side aisles and a passage around the east end.
Semi-circular chapels extend from each of the outer bays of the aisles that surround the nave, transept, and choir.
Because these chapels were planned from the start, their proportions and shapes were better integrated with the whole than the unplanned chapels that had been added to San Lorenzo.
The height of the nave arcade equals the width of the nave, which is defined by the crossing-square module.
The height of the nave arcade is equal to the height of the clerestory, meaning that the height of the nave arcade is half of the total height of the nave. The 1:1 ratio of nave arcade to clerestory at Santo Spirito differs from the 5:3 ratio at San Lorenzo.
The entablature does not touch the moldings of the arches below, which gives the spandrel area greater continuity than at San Lorenzo.
The increased plasticity of Santo Spirito, which gives Brunelleschi's later work a more sculptural and monumental character, tends to affirm that in 1433, he took a second trip to Rome, where these qualities could be observed at many ancient Roman sites.
The use of columns that are proportionately thicker and spaced closer together contributes to the church's monumentality.
The contours of the moldings project further outward and cast wider shadows.
The concave curves of the side chapels and the sail domes in combination with the convex curves of the columns and half-columns produce a ripple of curves and counter-curves.
During the completion of the church, Brunelleschi's architectural successors changed several features of its design.
Although Brunelleschi had intended that the aisle around the perimeter be continued across the entrance wall where its four bays would serve as an entrance foyer, only the outer two bays were completed as part of an outer aisle. The inner two bays were integrated into the nave.
In conjunction with the use of four bays for an entrance foyer, Brunelleschi had planned four doors on the entrance façade. Although architects like Giuliano da Sangallo campaigned against changing Brunelleschi's design, in the end, the façade was built with the traditional three doors.
Although Brunelleschi had intended for the exterior side walls to exhibit a series of convex forms in correspondence to the concave interior side chapels, a feature seen on some Romanesque churches, subsequent builders concealed the contours behind straight outer walls. Because the chapels were planned from the beginning, their proportions and shapes were integrated with the whole.
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Brunelleschi's Santo Spirito, Florence