Iwan

The iwan, or eyvan in Turkish, is a vaulted space enclosed by thick walls on three sides and opened on the fourth by a single large arch toward a courtyard or central hall. It sits between room and courtyard: shaded and sheltered, yet never cut off from the open air. The form is generally traced to Iran and became established in Anatolia under the Seljuks.

The iwan in Turkish architecture

In Anatolian Seljuk madrasas the iwan is the backbone of the plan. Scholars describe these buildings as two-iwan, three-iwan or four-iwan types, depending on how many open halls face the courtyard. The main iwan, opposite the entrance axis, is usually the largest and served as the teaching space. The same arrangement appears in caravanserais and inns, and in vernacular houses the iwan becomes a half-open sitting area off the central hall, used mostly in summer.

How it works structurally

The vault over an iwan carries its load into the two long side walls. Because the front is open, the side and rear walls must resist the outward thrust of the vault on their own, which is why iwan walls are noticeably thicker than those of neighbouring rooms. The front arch is often treated like a portal and sets the rhythm of the courtyard elevation.

• Main iwan: on the entrance axis, the widest and tallest
• Side iwans: on the cross axes of the courtyard
• Iwan arch: the large opening facing the court

In a measured survey, read the iwan in section together with its vault profile and wall thickness. In a 3D model, building the vault surface and the front arch as separate parts makes it easier to compare restitution options.