Jacki Heath has been a practising engineer since 1993. Since 1997 she has worked predominantly on historic and infrastructure projects. Here she discusses the Lighthouse Building, a Grade II listed structure which was on Historic England’s “Heritage at Risk” Register until its extensive restoration. The project has been shortlisted in The Structural Awards 2016 “Structural Heritage” category.
I was inspired to become a structural engineer because I enjoyed maths and I wanted a career which provided opportunities to work in various locations. I was also inspired by long span bridges, and the achievements of Victorian engineers.
Of the achievements in my career to date I would have to count the refurbishment of the Camelia Glass House at Chiswick House and the repairs to the south steps and floor in Westminster Hall as real highlights. There are other buildings I would love to help bring to life: a few years ago I inspected the Red House cold store at Smithfield Market, which dates from 1899 and was designed by Reeves and Styche. It was an amazing space and still contained some of the original cold store fixtures, trolleys and lifts, and with some structural interventions and sensitive repairs could create a fascinating building.
The Lighthouse Building has been a real pleasure to work on. When you set about revitalising a heritage structure like this it’s vital to understand the existing building - in terms of the materials that were used in its construction and the repairs and alterations that have taken place over its lifespan. From this point we use analysis and previous experience to develop a strategy for renovation that minimises alterations to the building’s fabric and respects the original design - while providing a new lease of life.
The project is a real example of how structural engineers can unlock the potential of derelict buildings. The Lighthouse Building was on a difficult site, with traffic all around and two cut-and-cover tunnels underneath. We used soil interaction models to prove that adding more storeys to the building was viable, which in turn unlocked investment and secured confidence in the restoration from our client. Network Rail and Transport for London (TfL).
It was a challenging project, not least because of the two underground tunnels running beneath the structure. The principle method of dealing with this issue was to allow the original structure, such as the façade walls and lighthouse, to continue to vibrate just as they always had done - with the new steel frame and finishes isolated with elastomeric bearings and isolation material. The theory was simple but, as with everything, success was down to mastering the detail.
We liaised very closely with Network rail and TfL to ensure they were happy with the principles of the design, and used our analysis and design skills collaboratively to enable the architect’s vision to be realised. We also developed a comprehensive movement monitoring strategy to prevent delays or stoppages.
The constraints of the site, such as the Flat Iron building shape, the need to retain the existing façades, and the location (adjacent to King’s Cross station), all informed the architectural design - at an early stage the architect considered opening up the basement by removing walls but this was not possible as the walls were needed to support the columns, and we could not accommodate additional storeys and basement load.
Throughout, the engineering requirement to maintain a constant load on the tunnels defined the demolition and construction sequence, with work being done bay by bay.
The completion of the lighthouse after many years of effort and plenty of site challenges was hugely satisfying. Of course much of the hard work in the structural design is hidden behind the striking architecture but, in a way, that is the point. I am very proud to have been part of the team delivering such an unusual building, it was so good to see it actually finished and we are delighted to see it shortlisted for a Structural Award.
Learn more about The Structural Awards.
(Image credit: Daniel Shearing)