The history of Qasr Al Hosn
Originally constructed in 1760 as a single watchtower guarding Abu Dhabi’s freshwater well and coastal access, Qasr Al Hosn has evolved over the centuries into a symbol of the city’s growth and resilience. Between 1790 and 1816, additional towers were built to form a defensive enclosure overseeing key shipping routes, and between 1939 and 1945, the outer palace was constructed.
Over its centuries, the fort has undergone significant evolution. Serving as a royal residence, seat of government, military headquarters, national archive, and, most recently, a museum, displaying artefacts and archival materials dating back to 6000 BC.
The challenge
Decades of modern interventions had left the fort’s masonry and render severely compromised, with extensive corrosion, concrete spalling, and persistent damp.
Particularly affected were the traditional vented wall structure, known as the Barjeel, and the render of one of the main towers. The cement-based materials used for prior remedial works were too rigid for the original masonry and unable to accommodate structural movement. Over time, this incompatibility had caused large voids to form within the wall, weakening its structural integrity. It had also caused cracking and delamination on the exterior of the main tower, exposing the soft coral stone to the elements.
With the structural stability and distinctive façade at risk, the challenge would be to effectively stabilise the compromised masonry with materials fully compatible with the original historic fabric, while protecting the building’s iconic appearance.
Technical & aesthetic considerations
Preserving the authenticity of Qasr Al Hosn required a meticulous understanding of its original materials and construction techniques.
The Barjeel wall structure, built from soft coral stone, is an integral element of traditional Emirati architecture. Impaired by large voids, it would require grouting to restore its structural stability. If the custom grout were too strong, it would not allow for structural movement and drive water into the background substrate, causing further damage and erosion to the masonry. But if too weak, the grout would not provide enough reinforcement to adequately restore the wall’s structural integrity.
The building’s traditional finish, along with the public’s affection for its distinctive exterior, would also require careful consideration. Originally coated in a lime-based render made from local sand and crushed seashells, the building had a distinctive bright-white appearance, earning it the nickname “White Fort.”
The solution
Working closely with specifiers, consultants, and conservation experts, our team developed a custom-engineered, low-strength grout and a historically accurate, yet functional, render tailored to the specific requirements of Qasr al Hosn.
Using 100% pure natural hydraulic lime, graded powdered mineral fillers and conservation-appropriate additives, a low-strength grout was custom-engineered. Its fine texture enabled it to reach and fill the smallest of gaps, while its high flow rate eliminated segregation and blockages.
The grout’s flexibility allowed for structural movement, and its high porosity supported moisture management by combating water penetration and pooling inside the masonry. This solution ensured a durable, resilient bond between the grout and the masonry, critical for long-term structural integrity.
For the external render, an exacting blend of anhydrite, brick, charcoal, and sand was created to replicate the colour, mineralogy, and grain size of the original lime-based material. A DAkkS-accredited laboratory independently tested the render to verify compliance with specification requirements for composition and minimum strength. This rigorous testing confirmed that the new material would perform in harmony with the structure whilst accurately representing the history of the original material.
The result
Through this collaborative, research-driven approach, over 150 tonnes of bespoke masonry grout were supplied to fill and stabilise the voids within the Barjeel wall, while the main tower was successfully restored using the custom-engineered render. The result was a strengthened and stabilised structure that retained its original character and visual harmony.
“The success of this intervention was such that the custom-engineered low-strength grout became our most popular.”
ADAM BROWN, COMMERCIAL DIRECTOR
After more than a decade of intensive conservation and restoration, Qasr Al Hosn stands as a vital heritage landmark and a testament to how cutting-edge techniques and traditional materials can preserve history for future generations. In 2021, this remarkable site was recognised with the Gold Accolade at the World Architecture News (WAN) Awards, outperforming six world-class competitors in the ‘Mixed Use’ category. A fitting achievement for an exceptional landmark.
