Building on history: renovating and preserving the Engineering Building roof

When the roof of such an iconic building as the Engineering Building has reached the end of its useful lifespan, how do you go about replacing and preserving something so groundbreaking whilst retaining the original vision and innovation?

In 2011, the University announced a major project to preserve and enhance its Engineering Building and in 2015 work began on replacing the roof, which was reaching the end of its serviceable life, to extend the building’s functionality and iconic status for another 50 years.

It’s a fine balancing act but then the whole project has been a story of compromise, finding the perfect marriage between conforming to contemporary standards and preserving the innovation that made this building unique. As the final result is revealed the full extent of the efforts to modernise this iconic building can finally be appreciated.

Overseeing an icon

The Grade II* listed Engineering Building is considered an architectural icon across the globe, hailed as one of the top 10 most inspiring buildings in the UK, included by The Daily Telegraph in 2008 in a national list of the fifty most famous structures in the UK and featured in numerous books of British architecture. The stunning roof design, with its bold diamond-shape profile, has even graced a postage stamp.

Project Manager Pete Bale (pictured left) has overseen the project since its inception in 2010. The plan was to honour the intentions of the original architects, but that also meant working around the large deviations and misalignments of an older structure and today’s much stricter performance and safety standards.

Reflecting back upon how he became involved in the project, he said: "The overwhelming emotions at the start of this project were of excitement and optimism. As a construction professional the prospect of undertaking this sort of conservation work on such an significant iconic building is a once in a lifetime opportunity, and really, how difficult could it be? We were soon to find out!"

New, modern and innovative

Two years after the University was granted its Royal Charter in 1957, the University was in discussions with the young architects James Stirling and James Gowan about a new building, to be completely at odds with university architecture of the day. The brief reflected the confidence of a newly independent university and an eagerness to embrace the modern and the innovative.

Rejecting traditional approaches and reacting against the functionalism of contemporary architecture, the short-lived Gowan-Stirling partnership aimed to design each building in a style that reflected its use. As Leicester’s new building was to house the recently established Engineering Department, they incorporated ambitious geometric elements such as the cantilevered lecture theatres.

That ambition would bring its own challenges. The complex roof, set at a 45° angle to bring north light into the workshop block below, required an innovative frame of rectangular and diagonal shapes that end in a striking diamond pattern.

But the roof was fabricated using a lightweight aluminium stick system that was assembled by hand on site, unlike today where such complex designs would be designed and manufactured to strict tolerances.

The result, though an awe-inspiring display of geometric dexterity, was not built to last but a refit would require rebuilding every individual section – each of which was unique in form and construction – from scratch. Like most ambitious constructions it suffered its fair share of leaks and draughts but complete replacement of the roof was an option suggested in hushed tones.

Securing the future

And the Engineering Building is a Grade 2*-listed building which brings even greater restrictions to what work can be undertaken.

Pete Bale said: “The idea of removing the old roof and installing a new one, with the same shape and using similar materials, might sound simple, but in reality it is immensely difficult.”

There are 2,500 glass panels that adorn the workshop block and every single one of them is unique. The steel frame that formed the roof has been wrapped in a weathertight glass and aluminium skin, but due to years of natural movement and warping in the structure each panel had to be shaped to fit. To meet current standards the glass thickness was increased from 9mm to just under 30mm, increasing the weight of the roof and requiring the glazing bars to be strengthened.

The £19.5million endeavour was entered into under the watchful eye of the Local Authority, English Heritage, the Twentieth Century Society and Historic England. Local community groups and key figures in the architectural community were consulted.

Every decision was considered carefully and with awareness of the influence and respect for the building. From this came some creative solutions to the challenges posed by the project, from exact heritage replicas of the original air handling units in the façade for ventilation, to a fabric envelope around the building mounted on a bespoke scaffold to allow work to continue in all weather.

For the first time, the University developed a Project Charter with its management contractor Lendlease, the other trade packages and the key stakeholders. All parties committed to working in partnership and to maintaining the historic building’s status, such was the determination to ensure that this project was done properly.

The result is a faithful a replica of the roof that represents the skill, expertise and dedication of the project team and all its partners. Pete Bale said: “The new glass roof and façade to the Stirling and Gowan Engineering building, has exceeded the expectations of all those that can now see it, including many within the project team.

“The reproduction of the original detailing has brought new meaning and life to the old structure. The way the light changes and reflects on the facets throughout the day is truly beautiful, and is testament to the original design. I am immensely proud to have been involved in the restoration of this iconic building for the University and future generations.”