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DIFA tower (1)

City of London

Commercial tower approximately 300m in height on Bishopsgate in the City of London. Designed by Kohn Pedersen Fox (KPF).

21 November 2005

Planning reference: 05/00546/FULEIA

Tagged with: Commercial | Design review | Design review panel | London | Tall buildings

CABE has reviewed this proposal for an office development on Bishopsgate in the City of London, known as the DIFA tower, on a number of occasions, most recently in 26 April 2007. CABE also commented on this scheme in November 2005 and March 2005, both of which are below.

CABE comments, November 2005

We wish to make the following observations about the planning application and the latest revisions to the scheme.

We are pleased to note that the City has commissioned Lovejoy to undertake a public realm enhancement strategy for the eastern cluster which we suggested would be of value for the proposed and consented schemes coming forward. We have not commented on this document but we trust that it takes account of the issues raised above in relation to the public realm surrounding this proposal.

We are also pleased that the ground floor of the building is now being thought of as an extension of the public realm which has, in our view, resulted in a more convincing proposition for the public space and route.

In terms of the architecture we wish to reiterate our comments about the 'sliver' building and 1 Great St Helens as well as the detailed design of the canopy. We have seen illustrations, which do not form part of the formal planning application submission, that seek to address these issues. The City will need to be satisfied that our concerns regarding the design detailing can be resolved in the subsequent stages of design development.

In relation to the top of the building we previously stated that we would not be averse to a taller building if the outcome was a more definite termination to the building. In May, we were of the opinion that the termination to the building had been improved. We did not formally comment on the taller proposal.

In our view, the work now done to resolve the top of the building has been successful for the submitted scheme and therefore we have no difficulty with the building's new, shorter height.

As with all tall building proposals CABE wishes to make the following points;

We strongly believe that for this building to be regarded as a success and therefore to receive the support of CABE, public accessibility to a high level in the building must be guaranteed. We think it reasonable that restricted public access, such as is available in other neighbouring buildings is offered. In addition, we would wish to see this space more accessible to a wider number of people on a (limited) number of occasions, such as Open House weekend. We think it vital that this degree of public access is enshrined within any planning consent and therefore that it is enforceable.

As with any building, but particularly one of this scale, much of the success will depend on the design detailing and the quality of the materials and construction. As we have said on previous projects, if built, this will become one of the most prominent buildings in London. We think it reasonable, therefore, to demand the highest and most exacting standards of design. It will be important for the planning authority to satisfy itself that any planning permission guarantees that those standards will be achieved in the end product.

CABE comments, March 2005

We are pleased to be offered the opportunity for the Panel to review the design evolution of this scheme since the initial Panel review in November 2004, the Commission meeting in December 2004 and the informal meeting in January 2005.

We are also pleased to hear that the architects and client found our comments helpful and constructive. We continue to believe that the architecture of the proposal holds great promise and that the more time is allowed developing the design the more convincing the project becomes.

We reiterate our comments that this scheme demands assessment against the highest standards of quality and it should not go ahead unless it can be demonstrated both that the design reaches such quality standards, and that the finished product will measure up to the design proposals. This will require commitment from the client and the local authority as much as the architects.

While welcoming the considerable progress made refining the design over the past few months, we believe that a number of important aspects of the design still need considerably more work. This is particularly true of the public realm.

Public realm

We are encouraged that a landscape architect, Georg Penker, has joined the design team to re-examine the public realm issues and that constructive discussions with the promoters of the adjacent 122 Leadenhall project have taken place. However, we continue to believe that, given the scale of this project, a significant public space is required and one that makes sense in the wider context of the city. We continue to believe that the current crop of tall buildings in the immediate vicinity of this proposal would benefit from a coherent public realm strategy and that this is a task which the City should take responsibility for initiating.

In our view, the design of the public realm is a design challenge in its own right. We suggested previously that a successful outcome is more likely to result from trying to design a high quality public space that respects the site, its historic development, and its context than from treating as a priority the notion that the present configuration of Crosby Square should remain recognisable. In departing from the original concept of retaining Crosby Square and seeking to resolve the ambiguity between the ground plane and the undercroft of the building, the design team has, in our view, made a key step toward developing a coherent public space and an entrance to a building. We hope that this thinking continues to inform the design. However, it is still unclear to us how this space will be used, and how it will work at different times of the day and year.

We would like to see the public realm extended into the building itself with genuine public rather than commercial space both in the lower levels and at high level.

We consider that the public space should be one of the most valuable outcomes of this project. It has great potential and its development represents the opportunity to create something unique that, by virtue of being partially covered by the tallest building in the city, could be astonishing. In our view, it is still some way from achieving this.

Architecture

In our previous letter, we recognised the skills of the architects in creating a striking and potentially beautiful building. We continue to believe this is so. However, we raised concerns about two aspects of the building at the lower levels, the design of the accommodation adjacent to 6-8 Bishopsgate and the design of the canopy.

We are not persuaded that the architecture of the 'sliver' adjacent to 6-8 Bishopsgate, and the proposed addition to 1 Great St. Helen's, have undergone the same rigorous design analysis and development as the rest of the building. We understand that their design is constrained in part by practical considerations. Nevertheless, we think that further work is needed to determine the extent to which these fragments are seen as either separate, contrasting architectural elements or as sharing a common language with each other and the building above.

In proposing such a large building on this site the architects have created a set of problems requiring technical as well as aesthetic resolutions, particularly relating to the adverse impacts of wind. Providing a canopy large enough to deal with these problems is a difficult enough design challenge, but in addition the canopy needs to be modified to respond to the existing buildings adjacent to the site, notably 1Great St. Helen's. The City will need to be satisfied that this proposal does not have a detrimental effect on future redevelopment. Indeed, we wonder whether the ability to secure the redevelopment of 1 Great. St. Helen's may not result in a better project all round.

Previously, we suggested that the language of the canopy should be more influenced by the form of the public space, rather than as a continuation of the tower. We still think that this approach has merit. We realise that what we are being shown is work in progress but we are concerned that this aspect of the proposal is in danger of falling between two stools; in being a continuation of the tower as well as being a covering for a public space. In our view, it could be helpful to think of the structural requirements of the canopy as either being clearly derived from the structure of the tower, or seen as a separate piece, referred to as a 'belt' in our previous letter.

It will also be important to demonstrate how the 'hem' of the canopy will be finished. As currently illustrated it appears too substantial and hefty in relation to the rest of the canopy and of the building itself. In our view, further detailed thought on this aspect of the scheme is required.

Given the difficult design task ahead, we are concerned that the complexity of the geometry of the canopy structure means that an elegant and potentially beautiful solution will require a level of scrutiny and control by the architects which is not usually associated with such large construction projects. We fear that it could be impractically complicated to design well and prohibitively expensive to construct to the standard required.

The further work to resolve the design of the top of the building in terms of the skin and the structure is encouraging. The use of a liner, as an architectural device as well as a functional one containing the maintenance cradle, seems appropriate. We understand that work on the form and shape of the top of the building is continuing. We would not be averse to a taller building if the outcome of this was a more definite termination to the building.

We welcome the consideration of colour in the elevation by using the liner to define the top of the building, the notch in the western façade and the edge of the canopy. However, this needs careful handling to ensure that it relates satisfactorily to the architecture and aesthetic of the remainder of the building. We think that the involvement of an artist could be beneficial in this respect.

Materials

We continue to believe that much of the elegance of this building is derived from its structural carcass - the heavier bracing at the lower levels diminishes towards the top. We find the earlier development models to be compelling in this respect. It is regrettable that the performance requirements of the glazing are unlikely to permit a level of transparency that would allow this bracing to be expressed through the façade.

We note that additional work has been carried out to demonstrate the role of the all glass façade in the energy strategy for the building. It will be important that the implications of this are tested against any new regulations. We are encouraged that the project will also be tested against the Mayor of London's energy policies and that a target of generating between 5 and 15% of its own energy consumption has been set.

Conclusions

We continue to support the broad ambitions of this project and believe that this proposal has the potential to be a high quality addition to the emerging cluster of tall buildings in the city and to the skyline of London. We applaud the continued commitment of the client to a first class product.

We reiterate our support for the architects and our confidence in their ability to achieve the high standards required, and to address the points we have raised above. We would welcome the opportunity to review this project again and suggest that any further meeting focuses on these aspects of the design.

CGi of the Difa Tower on the London skyline