Computer simulations of a 2,800-year-old monumental building in northern Ethiopia suggest its unusual timber-reinforced walls were strong enough to support far more floors than archaeologists had previously assumed.
An ancient palace in Ethiopia dating to around 800 BC could theoretically have risen to as many as 16 storeys while remaining structurally stable, according to a new engineering study that sheds light on the sophistication of early building techniques in the Horn of Africa.
Researchers used modern computer modelling to investigate the Grat Be’al Gibri at Yeha, a monumental palatial and administrative complex measuring roughly 60 metres by 60 metres.
The building is considered the largest known palace-like structure from the early first millennium BC in South Arabia and East Africa. Although only parts of its ground floor and massive foundation podium survive, archaeological evidence has long suggested it was a multi-storey structure.
Its walls were constructed from locally sourced phonolite rubble stone and clay mortar, reinforced with layers of wooden beams. Unlike comparable ancient building systems in South Arabia, where timber was commonly arranged both horizontally and vertically, the beams at Grat Be’al Gibri were installed exclusively horizontally.
The researchers set out to determine whether this unusual construction technique could have supported the substantial building represented in archaeological reconstructions.
Using a virtual three-dimensional reconstruction of the palace, engineers created finite element models of two representative sections: an external wall corner and an internal wall containing a doorway. The simulations accounted for uncertainties surrounding the mechanical properties of the ancient stone, clay and timber.
The results indicate that the building's walls had considerable structural reserves.
Previous virtual reconstructions had envisaged five regular floors topped by three recessed storeys. The new analysis found that this eight-storey reconstruction was comfortably within the walls' theoretical load-bearing capacity. Even under the researchers' worst-case assumptions about the building materials, the structure could theoretically have supported around 16 storeys.
The result does not mean that Grat Be’al Gibri actually had 16 floors. Rather, it demonstrates that the surviving wall system was capable of carrying substantially more weight than the reconstructed building would have imposed.
The simulations also produced a surprising finding about the timber embedded in the masonry.
Variations in the mechanical properties of the wood had relatively little effect on the overall load-bearing capacity. Instead, the properties of the stone-and-clay masonry were much more significant, with tensile failure in the clay-mortared rubble emerging as the critical structural limitation.
Archaeological evidence nevertheless suggests that timber selection was deliberate. African olive and Cordia africana have been identified among the beams, both woods with properties that include resistance to pests such as termites.
The palace's substantial construction provides further evidence of its scale. Ground-floor walls were approximately 1.9 metres thick, while the foundation podium walls reached about 2.2 metres. The podium itself was approximately six metres high, while monumental stone pillars at the entrance rose to about 10 metres.
Other archaeological features, including a staircase, also indicate that the building extended well above the surviving ground floor.
The researchers conclude that ordinary structural loading is unlikely to explain the palace's destruction. Given the considerable load-bearing reserves identified in the simulations, an exceptional event would have been required to cause catastrophic failure.
That conclusion is consistent with archaeological evidence showing that Grat Be’al Gibri was destroyed by a devastating fire in antiquity.
The study provides a rare engineering perspective on ancient architecture in the region. Researchers say there have been few structural analyses capable of testing how many floors ancient South Arabian and East African buildings could actually have supported.
The findings suggest the builders at Yeha had developed highly effective construction techniques through practical experience and the transmission of technical knowledge, allowing them to create monumental architecture centuries before modern structural engineering.
Further modelling could investigate the palace as a complete structure, examine the effects of different arrangements of timber reinforcement and incorporate more detailed floor loads and material behaviour.
The research, by Martin Drieschner of Brandenburg University of Technology Cottbus-Senftenberg and Mike Schnelle of the German Archaeological Institute, was published in the journal Heritage in July 2026.
Sources : MPDI - 10.3390/heritage9070270