Shibam Tower Houses

Shibam, in the Hadhramaut valley of Yemen, is a walled town of about 500 tall mud-brick tower houses packed together on a rise above the wadi floor. Often called the "Manhattan of the Desert", it is a UNESCO World Heritage site (the Old Walled City of Shibam) and one of the most striking demonstrations of what sun-dried earth can do as both wall and roof.

The buildings

The houses rise five to eleven storeys, with some over 30 m (98 ft) tall, and each floor usually holds one or two rooms. UNESCO describes towers of up to seven storeys rising from the cliff edge. All are of sun-dried mud brick. The walled city in its present form dates from the 16th century, after a flood in 1532-33 partly destroyed an earlier settlement, and many houses have been rebuilt several times since. The settlement itself has pre-Islamic origins and became the Hadhramaut's capital after about AD 300.

Earth roofs and maintenance

On a mud-brick tower, the flat roof and the parapets are the parts most exposed to rain and sun. Wind, rain and heat steadily erode the earth surface, so walls must be routinely maintained with fresh layers of mud. A rehabilitation programme run by Yemen's General Organization for the Preservation of Historic Cities (GOPHCY), with German support (GIZ) since 2000, documented 98% of the traditional houses and rehabilitated more than 60% of the private ones.

Threats

• Flooding is the most serious risk. A tropical storm in October 2008 flooded the city, weakening foundations; some buildings later collapsed. The abandonment of the traditional flood-management system has made things worse.
• Water and drainage: piped water without adequate drainage overloads the traditional sanitation systems.
• Concrete: replacing traditional materials with concrete, and new concrete buildings nearby, threaten authenticity.
• Conflict: the city was damaged during the Yemeni civil war, and UNESCO placed Shibam on the List of World Heritage in Danger in 2015.

Related

Sana'a, also on the World Heritage list, has tower houses of rammed earth and fired brick over stone ground floors. Both show that tall earth buildings survive only as long as their roofs and wall heads are cared for.