Columns in Company

A single column is a demonstration; architecture begins when columns are put together. This chapter is about the rules that govern columns in company: how far apart to set them, how to stack one order above another, and how to combine the column with the arch, the great Roman invention that the Greeks never adopted.

Spacing

Vitruvius names five spacings, measured as the clear distance between columns in lower diameters. The pycnostyle is the closest, one and a half diameters; the systyle two; the eustyle, which he recommends, two and a quarter with a wider central bay of three; the diastyle three; and the araeostyle anything wider. The spacing is not an independent choice: Vitruvius ties it to the height of the columns, making them stouter as the gaps between them widen, because a column seen against more air looks thinner.

There are practical limits too. A stone architrave cannot span much more than three diameters without cracking, which is why the widest spacing requires timber. In the Doric order the frieze imposes its own discipline: the triglyphs must fall over the columns and the metopes must be square, so the spacing comes in fixed steps (see The Doric Order).

One order above another

When a building has more than one storey, the orders are stacked in the sequence of their strength: Tuscan or Doric at the bottom, Ionic above, Corinthian or Composite at the top; the heaviest carries the lightest, as a strong man might carry a child on his shoulders. The upper columns stand exactly over the lower ones, axis above axis, so that solid always rests on solid. And each upper column should be shorter: Vitruvius, for the two-storey colonnade of a basilica, and Palladio after him, make it a quarter less than the one below.

℟Stronger below, lighter above

When orders are placed one above another, put the stronger below and the more delicate above (Doric under Ionic under Corinthian), and make each upper column a quarter shorter than the one beneath.

upper column = ¾ lower column; order sequence: Tuscan → Doric → Ionic → Corinthian → Composite

The Colosseum (AD 70–80) is the grandest example of superimposed orders, with Tuscan-Doric, Ionic and Corinthian half-columns on its three arcaded storeys and Corinthian pilasters on the attic above. Its storeys are nearly equal in height, which gives the building its tremendous, even rhythm; the Renaissance generally preferred the diminishing storeys that Palladio prescribes. Try both in the figure at the top of this chapter.

The arch and the order

The Greeks built with columns and beams. The Romans built with arches, vaults and concrete. Then, not wanting to give up the dignity of the Greek orders, they applied the orders to their arched walls as a kind of frame. In the Theatre of Marcellus and the Colosseum, each arch springs from a massive pier; an engaged half-column stands against the face of each pier; and a continuous entablature runs across the tops of the columns, over the crowns of the arches. The arch does the structural work; the order gives the measure and the dignity.

℟The arch framed by an order

Set arches on piers and frame each bay with an engaged column or pilaster carrying a continuous entablature, so that the arch does the work and the order gives the measure.

arch height ≈ 2 × arch width (Vignola); impost at ⅔ of the column

Vignola gives an arcade for every order, with and without pedestals, and a simple proportion that governs them all: the clear opening of the arch is twice as high as it is wide, and its crown stops just below the architrave. Because the column height is fixed by the order, the arch’s width follows from it, and the piers are sized to take the columns. The motif (sometimes called the Roman arch order or the Colosseum motif) became one of the building blocks of Renaissance and later architecture, from palace courtyards to railway stations.

Alberti took the logic of the Roman arch order to heart. For him a column was a piece of wall, and an arch should therefore rest on a pier rather than on a free-standing column; a round column under an arch was a contradiction. His contemporary Brunelleschi had set arches directly on columns in the loggia of the Ospedale degli Innocenti in Florence, and the argument between the two positions is one of the fault lines of the Renaissance.

℟The column is the chief ornament

In all architecture the principal ornament is the column: a part of the wall left standing and pierced through.

Pilasters, pedestals and the giant order

Not every column stands free. A pilaster is a flat, rectangular version of a column, projecting only slightly from a wall, with the base, capital and entablature of its order; it lets a wall be articulated into bays without the cost or the obstruction of real columns. A pedestal raises an order, allowing columns of reasonable proportions to reach a greater height or to stand above a balustrade. And from Michelangelo onwards architects used the giant order (columns or pilasters rising through two or more storeys) to give a façade a single, overpowering scale.

℟Vignola’s general rule: 4 : 12 : 3

Divide the whole height into nineteen parts: four for the pedestal, twelve for the column, three for the entablature. Without a pedestal, divide it into fifteen, giving twelve to the column and three to the entablature.

pedestal = ⅓ column; entablature = ¼ column

These combinations are the working vocabulary of classical design. With them an architect can compose façades of any size and any number of storeys while keeping every part in proportion to every other, which is exactly what the Renaissance meant by architecture.