Hagar Qim and Mnajdra Temples, UNESCO World Heritage Site
Walter Hunziker Architekten
Two special membrane roof structures now cover and protect the archaeological excavation of temple ruins Hagar Qim and Mnajdra.
To protect the 5,000-years-old temple ruins of Hagar Qim and Mnajdra on the island of Malta against further deterioration, engineers from formTL developed two special membrane roof structures, which now cover and protect the archaeological excavation.
The megalithic complex, constructed between 3600 and 2500 BC with limestone blocks weighing many tons, was recognized as a UNESCO World Heritage Site in 1992. The two stone temples are located 500 meters apart on the southern coast of Malta. Because of being buried for several thousand years Hagar Qim and Mnajdra were protected against decay before the excavation began in 1839.
The unprotected temple complex was directly exposed to the raw elements, and the soft limestone was deteriorating due to high-salt driving rain and large temperature fluctuations. As a result, a committee of scientists recommended in 2000 the “Conservation and Interpretation Protection” for the temple site according to UNESCO standards. This involved both weather protection and more respectful treatment by visitors to prevent further destruction of the fragile ruins.
Three important preconditions had to be taken into consideration in designing the membrane canopies: They needed to be deconstructable without leaving any visible effects at the excavation site, they needed to accommodate the astronomical alignment of the temple buildings so as not to obstruct sunlight on important days such as summer and winter solstice, and it was essential that they provide effective protection against the weather.
The geometry of the two canopies was only partly given due to the individual local topography, but could be solved similar in design: formTL developed two structures consisting of two centred, steel trussed arches, inclined slightly to the outside. Between the arches and to the perimeter a cable net with membrane panels is spanned. This biaxial cable net allows forming the arches without any additional stabilisation cables.
An additional challenge was protecting the excavation site during construction and the limitations which resulted: The temple complex could not be driven on or touched in any way, making the use of heavy machinery and scaffolding impossible. Thus, the complete cable and membrane structure had to be assembled successively by professional climbers and the roof panels were closed one after the other.
During the design process, the engineers of formTL adapted the roof shapes more and more precisely to the local topography. Step-by-step, they adjusted the structures with the gradually generated three-dimensional geometrical survey of the temples and their surroundings until all parameters were optimally fulfilled. Even the bearing points had to be changed multiple times, as they had to be archaeologically surveyed and inspected before approval.
The roofs are particularly protective because they offer protection against the elements in the direct vicinity of the temples. The soft, highly absorbent limestone now stays permanently dry since driving, high-salt rain hardly reaches the stones any more. The PTFE-coated glass fabric also filters the sunlight, reducing its original intensity to roughly 10 to 15 per cent. The stone-age limestone walls are thus protected against aggressive UV rays but can still be observed under natural lighting conditions.
Facts about Hagar Qim and Mnajdra Temples, UNESCO World Heritage Site
Size of the temple complex:
Hagar Qim: 1,744 m2
Covered area: 1,495 m2
Span of central arch: 54 m
Mnajdra: 2,890 m2
Covered area: 2,460 m2
Span of central arch: 68 m
Heritage Malta, Malta
Structural & membrane design:
Walter Hunziker Architekten AG
General contractor & manufacturer:
Last updated: November 17, 2012