Restoration breathes new life into fort

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  Topped by its decorative cupola, the imposing north-east tower of Qasr Al Hosn, known as Burj Al Hamam, or Tower of the Pigeons, has been stripped of its white render but its grey undercoat remains. Future conservation works will remove this layer as well to expose the tower’s original structure before a new render of traditional materials is applied. Christopher Pike / The National

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  Between 1979 and 1985, Qasr Al Hosn was restored using materials that were designed to achieve a pristine finish. The effect was smooth and hard-wearing but the unforeseen result was walls that were unable to ‘breathe’ because the modern materials shared none of the properties of the coral stone, which expands and contracts in response to changes in temperature. Heat trapped in the walls resulted in a layer of condensation forming, which not only caused the 1980s render to decay but was damaging Qasr Al Hosn’s original structure. Christopher Pike / The National

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  Artisans from Abu Dhabi Tourism and Culture Authority’s historic buildings team construct a mock-up room in the grounds outside Qasr Al Hosn. A kind of apprentice piece, the mock up allowed the team to perfect their skills and to train in the use of traditional materials and construction techniques before they started work on Qasr Al Hosn itself. Christopher Pike / The National

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  This tower, known to Qasr Al Hosn’s conservation team as B8, is believed to be monument’s oldest structure, dating from the 18th century. A more detailed analysis of construction is required before the outer layers of the 1980s render can be removed. Christopher Pike / The National

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  The removal of the outer layers of render from the walls of the palace courtyard has exposed the concrete reinforcement, introduced in the 1980s when this part of Qasr Al Hosn became the home of the National Centre for Documentation and Research. The work also revealed the mangrove wood lintels and stone ledger supports that were used in the construction of Sheikh Shakbhut’s new palace. Christopher Pike / The National

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  Individual layers of paint and render have been removed from the intricate ‘polylobe’ features that decorate the archways in Qasr Al Hosn’s internal facade. Originally, the polylobes were believed to date from the 1980s, but investigation has revealed layers of turquoise paint from the 1960s and render from the 1940s that prove these features are original. Christopher Pike / The National

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  The ‘White Fort’ in the 1950s. Built from materials that were available locally, Qasr Al Hosn’s walls were originally constructed from coral and sea stones and were rough-rendered by hand using a ‘beach plaster’, juss bahar, that was made of burnt and ground coral, sand and shells that would have glistened in bright sunlight. Ronald Codrai / TCA Abu Dhabi

Forget the new interactive exhibitions, the Vimto mojitos and the falcon displays – the issue that is certain to be on most people’s lips during this year’s Qasr Al Hosn Festival is the changing face of one of Abu Dhabi’s most important monuments.

Thanks to a conservation process that has stripped Qasr Al Hosn of the white render that has defined it since the early 1980s, the ‘White Fort’ has been replaced by something rougher, greyer and ultimately more complex.

“The festival always shines a spotlight of where we are with the works but this hasn’t been done because of the festival,” says Mark Kyffin, Abu Dhabi Tourism and Culture Authority’s head of architecture.

“You’ve just caught us at the end of one phase of work and the beginning of another. We now almost have an X-ray view through the building that’s providing us with a window into the construction techniques and building technologies of the past.

“By exposing it in the way we have we can understand where the building needs to be repaired and how the different periods of construction have become merged and interlaced with one another in a single elevation.”

The aim, Mr Kyffin says, is to return Qasr Al Hosn to something approximating its original state, with traditional materials giving the fort a more natural and historically accurate white.

That process started with a long period of archaeological and architectural investigation and is now about to enter its final phase. But before building could begin the fort’s outer layers had to be removed for preparation and the building’s health.

“In the 1980s, the building was covered with two coats of render on top of the original coral stone – a layer of grey cementitious render and a layer of white gypsum render on top of that,” Mr Kyffin says.

“That made it very difficult for heat to escape and resulted in the formation of a layer of interstitial condensation that caused the render to decay.”

That decay was the result of a material mismatch between the non-porous renders that were used when Qasr Al Hosn was restored and rebuilt in the early 1980s, and the original materials from the 1940s and earlier that allowed the fort’s walls to expand and contract with changes in temperature.

The beauty of Qasr Al Hosn’s original render – a form of beach plaster, juss bahar, made from burnt and crushed coral, sand and sea shells – lay in the fact that it was made from the same materials as the fort’s underlying structure.

This allowed the building’s walls and cladding to behave in unison and gave them insulating properties, absorbing the heat during the day and releasing it at night in a manner that helped to protect Qasr Al Hosn’s residents from the elements.

“We want to allow the walls to breathe again, to appreciate the manner in which the original building was constructed using coral and sea stones and to see the painstaking efforts the masons made at the time,” Mr Kyffin says.

“We want the building to be legible, so that the public can read each chapter of its evolution, so that its walls talk to the people of this place but also to allows others to understand how complex and how beautiful its fabric is.”