To describe the nature of constructing new structures behind a retained facade or maintaining an existing interior structure and replacing loadbearing elements of the facade.
SUMMARY
Restructuring a building generally involves replacing the internal loadbearing structural elements whilst retaining the facade although in some cases it might be the external structure which is replaced as part of a new cladding treatment. Such work requires careful consideration of the programme of construction and, in particular, the relationship between temporary and permanent work. Where permanent features can be introduced at an early stage to stabilise the retained parts of the building, it is possible to achieve some cost savings. Connections between the existing fabric and the new work, both temporary and permanent, need to be carefully designed, particularly with regard to loadings imposed on the retained structure and the effect of deformations of the new work on existing material, which may be fragile and brittle. At the same time, sufficient lateral rigidity must be provided to ensure stability. These principles are illustrated with a number of case studies.
There are many reasons for refurbishing a building. In some cases, the refurbishment is so extensive that only the original facade remains with the interior being totally reconstructed. This work might be described as restructuring and represents the most extensive form of repair or reconstruction activity associated with existing buildings. Although it could be more expensive than total demolition and new construction, it may be economically viable due to local planning or tax incentives. For instance, in the United Kingdom buildings originally built before the 1940s can qualify for an increase in the plot ratio allowing a larger lettable area than the equivalent new build structure on the same site. In the case of a building in Finsbury Square in London, two extra floors were added at roof level providing an increase in the lettable area for the client. Obviously, the economics of the more costly solution of restructuring needs to be considered against the option of starting again from scratch but achieving a smaller lettable area. In any case, re-use of an existing building will have favourable environmental impacts as material resources will be saved. In urban areas, limited transport and logistics should be taken in consideration.
Another important reason for restructuring rather than rebuilding is where the facades are of architectural or historical interest or where there are requirements for maintaining the existing character and appearance of an area. For example, in the central districts of Paris the Haussmann-style facades have to be maintained.
In Europe, many buildings which are being refurbished are basically of masonry construction with relatively low floor-to-ceiling height. The need to retain the existing facade is usually of greater importance to the planners than the retention of the interior structure. This type of refurbishment can mean temporary works for restraining the existing facade. In other cases, it may be the internal structure which is maintained whilst modifications are made to the facade.
In this lecture, the construction principles of restructuring are discussed and some typical examples described. They illustrate how steel can be used to satisfy both the structural and architectural requirements.
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