Qadad

Qadad (Arabic: قضاض qaḍāḍ) or qudad is a waterproof plaster surface, made of a lime plaster treated with slaked lime and oils and fats. The technique is over a thousand years old, with the remains of this early plaster still seen on the standing sluices of the ancient Marib Dam.

Volcanic ash, pumice, scoria (Arabic: شاش), in the Yemeni dialect, or other crushed volcanic aggregate are often used as pozzolanic agents, reminiscent of ancient Roman lime plaster which incorporated pozzolanic volcanic ash.

Due to the slowness of some of the chemical reactions, qadad mortar can take over a hundred days to prepare, from quarrying of raw materials to the beginning of application to the building. It can also take over a year to set fully.

In 2004, a documentary film Qudad, Re-inventing a Tradition was made by the filmmaker Caterina Borelli. It documents the restoration of the Amiriya Complex, which was awarded the Aga Khan Award for Architecture in 2007.