Alem (finial)

An alem is the finial placed at the highest point of a dome, minaret, tomb roof or other crowning element. It is usually metal, made of a shaft of stacked spheres and topped, most often, by a crescent. It completes the silhouette and is one of the details that announces a building’s identity most clearly from a distance.

Role in the building

The alem adds nothing to the structure, but where it sits is technically sensitive. It stands at the crown of a dome or cone, the point where the lead or tile covering comes together, and that point has to stay watertight. It is normally carried on a spindle or timber post that passes through the covering and is anchored to the structure below. Wind load and lightning are the main concerns when it is maintained.

• Spindle or post: the internal support
• Spheres and collars: the stacked body
• Crescent or top piece: the final element

In survey and restoration

An alem is hard to measure. It is usually out of reach from the ground, so it is recorded by photogrammetry or measured directly once scaffolding is up. Restoration documents the original material, finish and fixing detail, and an alem taken down is often repaired before it goes back. In a 3D model it may look like a small detail, yet it changes the silhouette, so build it as a surface of revolution and check its top level against the survey.