Giuliano da Sangallo's receiving the commission was due in part to Lorenzo de' Medici's involvement with the church's construction. He designed a sacristy and entrance vestibule located to the left of the nave.
Before the commissioning of the Sacristy, Giuliano was involved in the controversy over the completion of the church's façade. Brunelleschi had designed a façade with four doors that corresponded with the four bays at the entrance end.
The building committee voted to finish the entrance in the traditional manner with three doors.
Giuliano, who stood with those who favored finishing the entrance as Brunelleschi had designed it, was unsuccessful in pleading with Lorenzo the Magnificent to intervene in support of Brunelleschi's design.
1489: Rotunda. In 1489, Giuliano submitted a model of the Sacristy. The construction was supervised by Salvi d'Andrea and Lo Scorbaccia over the next eight years.
1492: Vestibule. In 1492, Giuliano designed the Vestibule. It was constructed by Simone del Pollaiuolo, known as "Il Cronaca," over a three-year period.
Like Brunelleschi, Giuliano used pietra serena trim against white plaster walls.
Although the capitals are very elaborately carved, the sacristy's decoration is generally sparse, like Brunelleschi's.
Windows on the upper level are capped by pediments like those Brunelleschi used on the exterior of the loggia of the Foundling Hospital. Use of this form of window trim on interiors, however, had no precedent in Brunelleschi's work.
Like Brunelleschi's domes for the Old Sacristy of San Lorenzo and the Pazzi Chapel, the dome of the Santo Spirito sacristy is divided into compartments that each contain a lunette with an oculus at the base. Giuliano's dome differs in having eight instead of twelve sections.
The height up to the dome is equal to the width, as it is at the Old Sacristy.
In selecting an octagonal shape, Giuliano may have had in mind the baptistery of Florence Cathedral, which he had studied and recorded in drawings. At that time the baptistery was believed to have dated to Roman times.
The altar is located on the right lateral wall from the entrance vestibule.
The corners of the square space occupied by the Sacristy contain niches and large storage cabinets for storing the vestments and vessels used in celebrating the Eucharist.
Because the friezes of the entablatures contain no relief or other forms of decoration and their surfaces are indistinguishable from the rest of the walls, the upper system seems to be floating between the lower story and the dome.
A vestibule is located between the church and the sacristy. It was constructed by the Florentine architect Simone del Pollaiuolo, who was called "Il Cronaca." He had also built the wooden model for the vestibule.
The vestibule is as wide as the Sacristy and half as deep.
The vaulted ceiling rises from freestanding columns next to the outer walls rather than by the walls themselves.
The vestibule's barrel-vaulted ceiling was constructed using methods that Giuliano derived from the Roman technique of poured concrete construction rather than from construction using voussoirs. Giuliano had tested his new vault construction at his own house and then used it at the Villa Medici for both the recessed entrance portico and the salone.
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