Pediments

Pediments were originally triangular gables found on Greek and Roman temples. During the Renaissance and subsequent Baroque and Rococo periods, new and more complex shapes were introduced. Regardless of their shape or complexity, pediments remain a low-pitched form.

3a. Height to Width Ratio

A pediment’s height to width ratio depends on its size. Large pediments that are too high can quickly become overpowering and visually too top heavy. Meanwhile, if small pediments do not have enough height, they can appear diminutive. Therefore, as pediments become larger, their height to width ratio should decrease.

Because a pediment’s size is often related to how many columns it has, the following formula can be used to determine an appropriate height for a given width and number of columns:

Height =                4 x Width           
.               14 + Number of Columns

The below table has been populated based on the above formula and can be used as a convenient reference.

These ratios represent a best fit taken from multiple pediments. In reality, many existing pediments may be slightly shorter or taller. However, by using these ratios, you can be assured your pediment will have an appropriate pitch.

The six pediments below illustrate these ratios. The images have been sized so that all pediments have the same width.
Left to right top row is: Castle Grove in Ireland, the White House in Washington D.C. and the Athenaeum in Bucharest.
Left to right bottom row is: la Madeleine in Paris, New York County Supreme Court in NYC and Catedral Metropolitana in Buenos Aires.

3b. Coupled Columns

Coupled columns count as one column. For example, St. Paul’s pictured below would be considered to have four columns (not eight) and hence use a height to width ratio of approximately 0.22. For more information on coupled columns, see Guideline 2k. Araeosystyle intercolumniation.

3c. Inferred Columns

If a pediment does not have actual columns under it, the columns can often be inferred. Take Marble Hill House displayed below for example. The South façade shown on the left does not have columns, yet it is fairly easy to imagine where they would go if there were columns. They would naturally be placed at both ends of the pediment and in between the windows for a total of four columns. Therefore this pediment should have a height to width ratio of approximately 0.22. As can be seen from the North façade shown on the right, there are indeed four columns, placed exactly where we would expect them.

Pediments above doors or windows can be treated similarly. Often they do not have columns supporting them. However, a column on either side of the door or window can be inferred. Therefore for pediments above doors or windows, two columns should be used in the above equation resulting in a height to width ratio of approximately 0.25.

3d. Pediment Variations

The most fundamental variation on the original Greek triangular pediment is the rounded, or segmental, pediment. As illustrated by the Banqueting House below, the height to width ratio is the same for both triangular and segmental pediments. When a row of windows are surmounted by pediments, the pediments may all be the same shape – either all triangular or all segmental. However, it is quite common to alternate between the two forms.

Both triangular and segmental pediments can be varied further by using different options for the apex and base. These options are: standard, receding, and broken (also known as open). All the pediments shown so far have had a standard apex with a standard base. This is the simplest and most common form. However, any combination of apex and base may be used. For example, a pediment might have a broken apex with a standard base, or a recessed apex with a recessed base, or a recessed apex with a broken base. The following table illustrates these combinations.

3e. Raking Cornice

As illustrated below, entablatures can be divided into three main elements: the cornice, frieze, and architrave. The cornice can be further divided into the cyma, corona, and various bed mouldings.

In a pediment, the raking cornice is the cornice set at an angle. Using the NYSE’s pediment as an example below, it can be seen that the corona and bed mouldings should be doubled up and included in both the raking cornice and the horizontal cornice. However, the cyma should not be included in the horizontal cornice of the pediment, but only in the raking cornice.

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