Problem of the Corner in Renaissance Architecture

from PALAZZO MEDICI to PALAZZO della CANCELLERIA


When architects begin to create private palaces in the Quattrocento,
they follow the ideas for interior courtyards that were present in Ancient
Roman houses. The interior spaces were designed as squares open to
the sky (the Ancient Roman atria) and in many cases they were framed
on each side by open arcades with rounded arches.
1st EXAMPLE :  Michelozzo's MEDICI PALACE, 1445
While the Palace in Florence built for Cosimo the Elder and his family
on Via Larga (Via Cavour) looked like a fortress on the outside,

with large rusticated stones on the first floor and stonework exterior with projecting roof console on the top floors, the interior of the building, also designed by Michelozzo, gives a less fortified sense to the Medici residence:

He opened the courtyard to the sky to let in light and he set in place Corinthian colonnettes supporting
rounded arches with airy windows above the center of each arch. To make the courtyard look larger than it was, he extended the length of the arcade at the back, as we can see in the plan for the building:

If one entered at the bottom of the drawing, the space from wall to column at the
entrance is smaller than the space from column to wall at the back of the courtyard.
The enlarged space would have made the palace itself look more imposing on the inside, but while he gave that optical illusion to the viewer,  he inserted another which became problematic for future builders.
MICHELOZZO's CORNERS:

The corners of the Medici Palace courtyard appear to melt into the fabric of the
building. Michelozzo places two round arches next to each other at the corner and he shows us two windows above supported by those arches. The arches themselves, however, come to a point at the corner resting on one column only. The consequence of this decision is that, to many architects, Michelozzo's corners look weak, as though they could never support the two arches, let alone the windows above them. The viewer has an uneasy feeling when looking at the corners, as though they might collapse under the weight of the building. It is possible for the viewer to see the arches as continuing in a straight line rather than turning to the side aisle. The articulation of the space suffers in the optical illusion because it becomes harder to "read" the structure and shape of the space.
2nd EXAMPLE:  URBINO, PALAZZO DUCALE (by Francesco di Giorgio Martini as well as by Laurana) The exterior of the ducal palace made for Duke Federico da Montefeltro between 1470 and 1478 is less fortified than the Medici house, but it still has turrets with staircases and large pink bricks lifting it up the hill high above the level of the street.

The color of the bricks lightens the imposition of the place and the balcony arcades suggest a piercing of the wall of the castle. As one might expect, the architect follows similar rules to those of Michelozzo in planning the interior courtyard: the inner court is open to the sky, and it is a rounded Corinthian arcade that supports the two stories above it:

But unlike in the Michelozzo example, the space measuring column to wall is even all the way around the building, giving it a sense of solidarity to the eye. And Francesco di Giorgio handles the problem of the corners in a much stronger way than Michelozzo.

He reinforces the corners by several devices:
1) he makes the corner arches come down on or spring from a Corinthian column attached to a pier; this allows him to retain the spandrel roundels, strengthening the impression of the corners with two circles, two engaged (or attached) columns, and two pilasters. (The spandrels are the spaces above the two arches and in between them; here white moldings make a circle, a roundel within the spandrels.)
2) he supports the second story corners with the two pilasters joined at the base and he continues the theme of square support by repeating the engaged pilasters between windows in the second story.
3) he articulates the space of the corner as different from the rest of the arcade, therefore allowing the viewer to "read" the building as having sustaining parts that are strong enough to hold up the rest.
The "reading" also includes understanding exactly where the building turns the corner to form a square.
4) the Latin inscription which runs the length of the building in the architrave on both stories, praising the Duke of Urbino, has pauses or stops at the corners, which contribute to their literally being "read"as forceful elements for one side or another.
Martini's solution for the problem of the corner is to make it stronger by doubling up the elements. Some architects might object to this as being "heavy-handed" and say that it makes the courtyard too bulky, but the lightness of the stones (pink and white) tends to counter that heaviness and make his solution a viable one.
He creates another problem to be solved, however, in the process. His corner doubling forces the capitals of the pilasters on the first story to occupy the same space as the spandrel roundels. The uneasiness of this coexistence is visible in closeup views:

The spandrel roundels look like (parentheses) next to the pilaster capitals. The overlapping does not quite work and makes the viewer question the accurate measuring of the rest of the arcades.
3rd EXAMPLE:  ROME, PALAZZO DELLA CANCELLERIA (again by Francesco di Giorgio Martini? or Laurana, 1483-1517).
This later Roman example differs from its predecessors in two ways we might expect because of its location in Rome: it is LARGER, perhaps responding to the monumental quality of buildings in Rome, and the palazzo includes a church within its premises, the church of San Lorenzo in Damaso, since the palace was built for a Cardinal of the Church, Raffaelle Riario; Rome as the center of the Catholic Church may have some effect on the desire of the patron to build his home around an already-existing church, and his own job as cardinal of that church contributes to his desire to work not far from home.
The exterior is still a fortress with jutting tower battlements, but the interior courtyard is much as we might expect for a ducal residence.

How light and airy it is, and not just because of the color of the stone. Martini has decided that instead of windows on the second story, that he will continue the arcade theme from the first floor onto the second, opening up the space and creating walkways above and below on all four sides of the building's interior. He does not repeat the exact heights of columns and arches on both floors.  He tailors the second story by making the lengths of the columns 2/3 of the length of the columns on the ground floor, and he reduces the height of the arches to 2/3's the height of the arches on the ground floor. That proportional system, also present in the contemporary building of Santa Maria delle Carceri in Prato by Giuliano da Sangallo (church 1483-86), is a mathematical realization of measurements that are easy for the eye to comprehend and make for an aesthetic transition from first floor to second:

In the case of our Roman palazzo, the architect elevates the building even further by leading the eye up from first to second story by means of repeating arches, but then he repeats the columns' positions between arches on the third floor by placing an engaged pilaster in white stone between windows and directly over the same location of the columns on the lower two stories (similar, in fact, to the placement of the pilasters in Urbino.)The effect of these changes is to emphasize the vertical thrust of the building and make the building soar with light. It is a more welcoming courtyard than either of the previous two we have seen, a pleasant place to come home to for the patron.
          Martini's solution to the Problem of the Corner is, too, revealing. Instead of repeating elements as he did in the Urbino corners, doubling up the columns and pilasters and spandrel roundels, he decides to give the corners strength and articulation by making them one reinforced pier that supports the two arches coming together there.  These piers "read" as though the punctuation at the end of a sentence and are satisfying to the eye because, though they use some of the same stone (pink and white) that we see in the rest of the building, they are not round and so are not confused with the arcades themselves; they produce "endings" after the series of rounded arch elements and soft rounded columns on which those arches rest. He also eliminates the problems of doubling roundel and pilaster capital which occurred in Urbino by simplifying the arches' arrival at the pier and removing decoration in the spandrels down to the banding around the pier itself.

Within the spandrels he sets the cardinal coat-of-arms of his patron, stamping the building as the owner's and also referring to the occupation of his patron as the chancellor of the Vatican. These roundels with cardinal hat and tassels have not been removed, in part because the building's function is still that of the Vatican Chancellery, the tax accountants for the Pope, hence its name, Palazzo della Cancelleria. The money is not here, but the bookkeepers for the Catholic Church still work in the building.
            The result of Martini's solutions is that the building of the Palazzo della Cancelleria is light-filled, airy, but substantial and grounded, a joyful place to come into and to reside in, and because of the articulated corners, a place the visitor feels safe in and satisfied visually.
             Martini includes only one thing from Michelozzo's earlier work in reverse: he makes the space between wall and column as you enter the courtyard larger than the distance between column and wall at the visual end of the courtyard; perhaps the result is the same, though. The building appears more massive and grand, with the square courtyard open to the sky less likely to disappear into that sky and less likely to be subsumed into the space of the aisles.
             The changes in Renaissance residences within the Quattrocento may seem subtle compared with changes that take place in the Baroque period, but the architects are building on precedent and experiment in certain areas to give their patrons their latest thought about what makes a building embody "la bella figura."