The conservation of historic concrete buildings is a topic so rarely spoken about on a national scale, but last month it was thrown into the limelight as it was announced that the BT Tower, a well-known landmark in London, is set to be turned into a hotel.

In addition to consulting on the project with the new owners and project architects, Catherine Croft, Director of Twentieth Century Society and Subject Tutor on the Conservation of Historic Concrete course at West Dean, weighed in on the news:

What are the key considerations when it comes to planning the refurbishment of a building like the BT Tower?

The first task is to make sure that there is a full understanding of its significance—by which I mean ensuring agreement as to exactly what it is that makes it special, and how all the different parts of its structure and surviving fit-out contributes to that. Achieving that will  take a mixture of archive research and careful on-site observation and investigation, followed by sensible analysis—and communication of the results to the whole team, including the new owner. So a mixture of focussing in on the minutiae, stepping back to see the bigger picture, and lots of discussion.

Then working with the client to ensure their requirements can be compatible with preserving the significance, or if there needs to be a bit of rethinking of the brief. 

Can you talk us through why it’s so important to conserve historic buildings, such as the BT Tower?

Because of the unique stories they embody, and because they have the capacity to convey those stories to future generations, and make our cities more diverse, interesting and ultimately much richer than they would otherwise be.

What makes the BT Tower such an iconic landmark?

Its unique silhouette and design, the fact that it was the tallest building in London when it opened, and that because Fitzrovia has seen very little subsequent high-rise development, it is still very visible on the London skyline, and because of its recurring coverage in popular media—my favourite example still being The Goodies “Kitten Kong".

What challenges are faced when conserving historic concrete buildings?

It very much depends on the type of concrete, what condition it’s in, and what the building will be used for in future. By far the most common problem is localised spalling.  This is when lumps of surface concrete crack and fall off, and is caused by the steel reinforcement within the concrete corroding.  Corroded steel expands and the increased volume has nowhere to go—so it pushes off the surface concrete. In most instances, patch repairs, using a concrete mix very similar to that used in the first place can be a good solution, but finding suitable skilled contractors to carry out the work can be difficult.

Why is education so important when it comes to preserving the history of Britain’s architecture and buildings?

Understanding both the history and evolution of buildings, and the skills needed to repair them are crucial to achieving good results.  I can’t immediately think of a building example with the popular potential to match the infamous “Monkey Christ” incident (when a devout parishioner’s attempt to restore a painting of Christ on the wall of a church in Borja, Spain induced ridicule and dismay), but, for me, every time a concrete building is painted over, rather than simply cleaned and patch repaired, it’s a huge and incredibly damaging unnecessary mistake which will cost vast amounts to rectify.

With concrete repair education of mid-career professionals is especially needed, as concrete conservation is a relatively new field and is unlikely to have been covered when consultants or crafts people were originally trained.