Hybrid wall systems incorporating wood are playing an increasingly important role in modern high-rise construction worldwide, as recent examples in Sydney, Hamburg, Vienna, and Berlin demonstrate.The goal of such systems is a more sustainable construction process with lower CO₂ emissions by reducing the use of concrete and steel as building materials.

Recent research by the DAI shows that buildings with hybrid wall systems were already widespread in ancient South Arabia and in the Ethiopian-Eritrean highlands during the first half of the 1st millennium B.C.

Their walls consisted of mortar-bonded masonry and wooden beams and, of course, required no concrete or steel at all. It is considered certain that it was precisely this wall construction method that made it possible to erect multi-story buildings.

Until now, it has not been possible to determine how tall these buildings were. This was primarily because they were mostly destroyed by fire, and only parts of the lowest story have survived in the archaeological record.

Ancient sources by Arab historians mention structures with up to 20 floors, and such tower-like, multi-story structures are depicted in South Arabian rock carvings and wall paintings. However, there have been no structurally sound load-bearing capacity analyses of these complex wall systems to date.

An Ethiopian-German research project at the Yeha site, conducted by the Sanaa branch of the DAI’s Department of Oriental Studies and funded as a long-term project by the German Research Foundation (DFG), is investigating the largest palace known to date in South Arabia and East Africa, named Grat Be’al Gibri. This monumental structure features such a wall system consisting exclusively of horizontally laid beams.

An associated collaborative project with the Department of Statics and Dynamics at the BTU Cottbus-Senftenberg, led by Martin Drieschner (BTU) and Mike Schnelle (DAI), is conducting numerical analyses of the palace’s walls to determine their structural behavior and load-bearing capacity. The initial results show that the wall system used at the Yeha Palace was highly efficient and would have allowed for the construction of at least 19 floors – making this palace an ancient skyscraper. In subsequent phases of the project, the floor structures and the building’s geometry will be incorporated into the structural calculations.

The BTU has published more information about the palace’s technical features: https://www.b-tu.de/news/artikel/32371-btu-statiker-liefert-neue-erkenntnisse-zu-antikem-palast-in-aethiopien