Elephant foot pier

An elephant foot pier, fil ayağı in Turkish, is a very large masonry pier that carries a main dome and the arches around it. The name comes from its sheer bulk. It may be square, rectangular or polygonal in plan, is usually built of cut stone, and tends to become the dominant vertical element of the interior.

How the load travels

A main dome produces both vertical load and outward thrust. Those forces pass through the pendentives and great arches and gather at the piers in the corners. So the elephant foot pier does more than carry weight; it also resists the horizontal thrust of the arches and passes everything down to the foundations. Concentrating the load on so few points is what makes a wide, open interior possible between them. In the imperial Ottoman mosques the main dome usually rests on four, six or eight large piers.

Elephant foot pier versus pier

Every elephant foot pier is a pier, but not every pier is an elephant foot. Pier is the general word for a masonry support thicker than a column and usually angular in section. Elephant foot is reserved for the largest piers that carry the main dome. Builders often lightened their visual mass with niches, steps in the profile or decoration.

In survey and restoration

These piers are the key to a building’s stability. A damage assessment looks closely at any lean, cracking and crushing of the stone face. Take sections at several heights during survey, since the profile can change with height. In a 3D model, placing the piers and their sections correctly is the first step before the rest of the dome geometry can be fitted.