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Structures Restructured | Reusing old buildings

Somerset house from courtyard edw 1001862

Engineers renewing old buildings need the skills of a surgeon and an understanding of when less intervention can be more.

Giving a building a fresh lease of life does not always have to be complicated,” says consultant Alan Baxter senior engineering director Michael Coombs. He points to a little model of a long wooden beam spanning between two uprights. The beam bounces when pressed, but insert a simple wedge at each end, and it becomes stiff.

“This was the solution to problems at Seamen’s Hall in Somerset House in London (pictured above),” says Coombs. The hall forms the entrance to the Georgian building and above it, designer Sir William Chambers conceived a large open meeting space, the Portico Room. He had to design the long span floor of the Portico Room to span clear over the Seamen’s Hall below.  

Removing partitions

Over time the Portico Room had been divided into smaller rooms, and when the Somerset House Trust decided to remove the later partitions they found a series of steel hangers supporting the timber beam under the floor which had sagged and become bouncy. “The engineers dealing with the removal of these hangers proposed to replace them with large, long span steel beams cut into the fibrous plaster ceiling of the Seaman’s Hall from beneath. This was the obvious solution to the problem, but it is one that would have been very damaging to important historic fabric.  The trust was nervous and asked us to consider whether some other solution might be possible.”

This is where the Baxter approach to historic building renewal kicked in. “A lot of engineers judge an old building by modern standards and come to the conclusion that it shouldn’t be standing up.  But a vast majority of building stock is old. You can’t condemn these buildings because they don’t comply with modern standards; you have to understand why they are standing, how they perform and the construction techniques of the time,” Coombs says.  

“I like to use medical analogy – when you first come to an old structure you have to get a feel of its anatomy and condition. If the patient is old and delicate, a heart transplant could be too much, better to give them a tablet. It’s the same with buildings. If engineers don’t understand what they are doing, the operation they intend to carry out could cause more problems rather than solve anything.”

If engineers don’t understand what they are doing, the operation they intend to carry out could cause more problems

Alan Baxter employs conservationists and a historian to research old buildings before the engineers get to grips with the issues. At Somerset House, historian Robert Thorne did the research that enabled the consultant to conclude that the original double beam construction was not the problem.

On-site investigation revealed that timber shrinkage at the beam ends, dislodged the original timber wedges,   causing the bouncing. “We concluded that it was possible to reinstate the continuity of the main supporting beams by reinstating the wedges which we did with steel wedges,” Coombs explains. “Quick, simple,” and he adds with a smile, “cheap”.

Somerset House is one example of many historic structures that Baxter has worked on. Its forensic approach has given the firm a creative reputation in a difficult field, so it is often selected for tricky jobs – particularly when combining old and new structures such as at Damien Hirst’s Newport Street Gallery in London which won the 2015 Stirling Prize (see box). International bodies come to its doors for ground breaking work such as the restoration of Al Zubarah fort in Qatar – a World Heritage site.

Why do we service our cars every year and not our buildings, when they are much more valuable?

Old records and drawings are often key, and Coombs is horrified at the cavalier way they are treated by many clients and engineering firms who have often simply thrown them out.

“We are quite unusual in that we keep all our records in a well-managed archive. And that includes old software that we think we might need to read electronic records.”

Building information modelling (BIM) is of course, supposed to be the answer to the problem of lost records.

“It’s a wonderful idea, but will the BIM models be maintained in the way people say?” Coombs asks. “When things are not built quite as the model, who adjusts it?”

Older techniques are a challenge

Construction techniques from the 1960s and 1970s are another challenge for those looking to reuse and renew.

“The problem with most modern buildings is that you don’t know

what is inside the concrete. You hope that there is enough reinforcement, but you don’t know; you can occasionally find a drawing, but even so the only reliable option is carefully to open up selected areas of floor and have a look,” says Coombes.

“And it is a fair bet, that no one has ever done any maintenance. Why is that? Why do we service our cars every year and not our buildings, when they are much more valuable?”

“Most buildings need a thorough overhaul after 100 years, building services engineering every 30 years,” says Coombes.

Baxter’s current challenges include adding new space to the 1820s almshouses that form the Geffrye Museum in east London and the Anglican cathedrals of Liverpool and Coventry. “These structures were designed when engineers were trying new things and testing the limits of their knowledge. It’s going to be fascinating.”

Case studies

Al Zubarah Fort, Qatar

Al zubarah fort following repair. credit qiah university of copenhagen

Al zubarah fort following repair. credit qiah university of copenhagen

The fort was built in 1938 to protect the coast from raiders from Bahrain and was constructed from local limestone, set in a mud mortar and rendered. The original render has been retained, carefully consolidated and repaired. Decayed timber lintels and beams were replaced like for like and heavily used suspended walkways were re-laid with a reinforced limecrete, replicating as far as possible the original materials used in the building’s construction. A new staircase and platform were designed for one of the corner turrets to give visitors a panoramic view of the World Heritage Site, Persian Gulf and desert.

Client: Qatari Museums Authority/University of Copenhagen

 

Newport Street Gallery, London

Newport street gallery. credit victor mara ltd, prudence cuming

Newport street gallery. credit victor mara ltd, prudence cuming

The project involved the development of a series of Victorian warehouses at numbers 1-9 Newport Street. Three buildings in the centre were Grade II listed for their use in scenery painting. The machinery was documented and removed which enabled a new use for the buildings as part of a scheme developed with Caruso St John, to create a unified gallery space.

The design incorporated polished concrete floors, which had to be capable of carrying very high loads without cracking, and two new geometrically complex feature stairs. The new facades to numbers 1 and 9 are constructed in unjointed solid masonry to relate to the adjacent listed buildings.

Client: Damien Hirst

 

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