Accredited as a World Heritage Site by UNESCO in 1995, Edinburgh has more than its fair share of heritage buildings. The city’s architectural legacy reaches much further than the traditional sandstone edifices that dominate Princess Street, however, and includes important examples of post-war Scottish architecture.
One such building is Appleton Tower, an eight-storey facility that currently serves as part of the University of Edinburgh’s School of Informatics. Constructed as part of the university’s George Square development in the 1960s, the Alan Reiach, Eric Hall and Partners-designed building has been controversial since it was first built. Indeed, opposition to the stark modernism of the George Square scheme was such that some of the proposed buildings were never constructed. It continues to divide opinion today: Historic Scotland proposed that it should be listed in 2005, while in the same year it was nominated as an eyesore for Channel 4’s ‘Demolition’ programme.
Much of the building’s interior was refurbished in 2006 and the latest scheme to update and upgrade the building has seen a complete renewal of the building envelope, along with construction of an additional storey at roof level and a new feature entrance at ground floor level. The building’s ceramic tile-faced, precast concrete and aluminium frame glazed facades have been stripped out and replaced with Shackerley’s SureClad engineered stone ventilated facade system.
Slimline and lightweight
The new cladding was specified by Edinburgh-based LDN Architects in conjunction with Buro Happold Engineering.
As Ross Crichton from LDN explains: “We specified Shackerley’s SureClad engineered stone system to reference the building’s original aesthetic and complement other George Square developments while upgrading it to create a sleek, contemporary look.
“As part of the building envelope upgrade, which included replacing the original single glazing, the SureClad system also formed part of a strategy to improve the thermal performance, bringing the structure into line with current Building Regulations.” Specification of a SureClad engineered stone ventilated facade system also offered a cost-effective route to providing an aesthetic that echoed the appearance of the facade of the University Informatics Forum directly opposite. Meanwhile, it satisfied the loading capabilities on the remaining concrete structure and enabled full insulation of the building within a ventilated facade.
Several approaches to renewing the facades were considered and LDN Architects worked closely with structural and facade engineer, Buro Happold, to identify a system that would address the limited loading capabilities of the structure while delivering the required aesthetic. A SureClad system comprising engineered stone facade panels cut to 1363 x 1200mm and 1080 x 2123mm formats – with a thickness of just 15mm – proved the ideal response to these requirements.
Because engineered stone does not have the inherent flaws and defects of natural stone in its quarried state; it is a hard and strong material. This means that Shackerley’s SureClad engineered stone panels can be manufactured with a more uniform finish and a far slimmer profile, resulting in much lighter panels.
LDN specified a white honed engineered stone with a very subtle fleck from the wide SureClad range. The result is a building that has an evolving aesthetic depending on your vantage point.
Ross adds: “From a distance, the facade appears to be a clean, almost white monolithic surface, which complements the edifices of the adjacent university buildings. On approaching the building, the finish of the engineered stone panels comes further into focus, revealing the subtle variation in surface texture.”
While tests to the concrete building envelope revealed that it was still structurally sound, it was nevertheless coming to the end of its design life. Furthermore, there were problems with the single-glazed windows. Some of the opening elements were failing and the glazing was contributing to the building’s poor energy performance.
As a result, the scope of the project included removing the tiles, stripping out the precast concrete facades and replacing the single-glazed windows on the north and south elevations. An elaborate working platform was erected around the building to ensure the required functions within the building could remain fully occupied and operational throughout the programme.
On the north and south elevations, the concrete facade has been replaced by solid insulated panels that have been toggled into the new curtain wall facade which is supported off the face of the existing concrete slab. On the east and west elevations where there is little glazing, the facade has been infilled with insulated structural metal frame and board, which supports the SureClad engineered stone facade.
These new super-insulating substrates have been enveloped with the SureClad engineered stone ventilated facade, which was installed using Shackerley’s ‘Hang On’ system, a robust and sturdy cladding substructure specifically designed to cater for larger, heavier facade panels. The entire system was prefabricated off site at Shackerley’s ISO 9001 quality-accredited production facility in Lancashire, and was delivered to site as an installation-ready package. The individually-barcoded, large-format engineered stone facade panels were all supplied with installation brackets attached to the rear using sturdy stainless steel undercut anchors to create a safe, secure and stress-free fix.
With such large-format engineered stone panels, the facade system had to be tested specifically for the Appleton Tower project. Once it had been shown to meet all the required performance and sustainability criteria, installation of the facades commenced, starting with the lower floors of the building to capitalise on the summer recess when the campus was less busy.
Extended service life
The SureClad engineered stone ventilated facade has now been installed on all four elevations of Appleton Tower, along with the new ground floor extension that forms a feature entrance to the building. The proven mechanically-fixed facade system with its secure undercut anchorage will extend the service life of the building for decades to come. At the same time, it has allowed for its thermal performance to be greatly improved.
More than anything else, the use of Shackerley’s engineered stone has transformed the jaded and controversial Appleton Tower aesthetic. It has given the building a contemporary appearance that befits its status as one of the University of Edinburgh’s core buildings respecting the design intent of the original architects.