The latest in an AJ series looking at architects who have saved buildings from the bulldozers or given them a new lease of life.
With up to 40 per cent of carbon emissions coming from the construction industry, the profession needs to find ways of adapting the type of buildings it designs, and fast. The default option for any project should be to adapt and re-use an existing building, one of the key demands of the AJ’s RetroFirst campaign.
Our ongoing series seeks to celebrate the projects that save buildings from ruin or give them a brand new life.
Today we hear from Fred Pilbrow, partner at Pilbrow & Partners, about how the firm overhauled a Brutalist 1973 building in Kensington, while keeping a Boots store open.
Tell us about the project
The Kensington Building is a mixed-use, regeneration project designed by Pilbrow & Partners on behalf of AshbyCapital. The building provides 11,974m² of office and retail space. Construction was completed in April 2022.
We started with a 1970s building. Architecturally and urbanistically it had many shortcomings: its crude concrete façades detracted from its historic setting; its orthogonal, Brutalist massing eroded traditional street lines, and blank, inactive frontages at ground floor level created a hostile presence.
Yet the building had positive qualities that allowed it to be successfully refurbished. It had a regular and widely-spaced structural grid, good floor-to-ceiling heights and high live retail floor loadings.
We stripped the building to its frame and then extended the structure laterally to restore the historic building lines on Kensington High Street and Wrights Lane. We added three levels of accommodation above, which are set back behind richly landscaped garden terraces.
The building flanks High Street Kensington Underground station. We created a new galleria to provide 24/7 access. This arcade is lined by the renovated Boots unit on the high street and a parade of independent shops to the south.
What were the challenges of the existing building?
Even with a building as recent as 1973, the quality of archival information posed a challenge for the refurbishment. Our excellent structural engineers, WSP, needed to be confident about the structure and construction of the original building to allow its extension and remodelling. We researched archival sources (building control and London Metropolitan Archives) and supplemented the information with intrusive investigative sampling on site.
The onsite work married closely to the archival drawings and we were able to progress the refurbishment, both with confidence about the structural capacity of the retained superstructure and its longevity.
Boots’ pharmacy license was dependent on continuous trade and ISG, the main contractor, sequenced works to allow Boots’ ongoing operation.
Aspects of the refurbishment that have proved most successful were controversial and hard-fought at planning. We set the three new office floors back from the restored Wrights Lane frontage. Here, the offices face neighbouring residential areas and Royal Borough of Kensington and Chelsea council planners were initially resistant to allowing office access to the landscaped terraces.
Working with landscape architects Gillespies, we proposed a 3m planting strip outboard of the office terraces to provide a visual buffer between the terrace and facing residential. It also limited terrace sizes so you wouldn’t encourage large social gatherings.
We made the case that providing the offices with external access, as well as being good for wellbeing, also incentivised the commercial tenants to pay for and maintain the landscaping.
Had demolition or partial demolition ever been considered?
Our preference is to refurbish where the quality and character of the existing building allows. In this case it was immediately clear that the robust and generous dimensions of the department store formed a natural core to a re-imagined mixed-use building.
As well as the embodied carbon benefits of repurposing the existing sub and superstructure, there were significant benefits for the construction programme (a year less than a new build) and reduced disturbance with fewer deliveries associated with demolition and new construction.
To facilitate the creation of high-quality retail and office space, elements of demolition were required. We created the ground-floor arcade, a new side-core in steel and demolished the original rooftop plant and roof slab, which had inadequate loadings, down to the second-floor slab.
Certain elements, such as the steel-framed plant enclosure at high level, have relatively high embodied carbon, which, to a degree, balances the saving of the retained structure. The overall embodied carbon – 700 kgC02e/m² – is a very credible figure, but falls short of LETI’s target of 500 kgC02e/m².
Aside from retaining the original fabric, what other aspects of your design reduce the whole-life carbon impact of the building?
The building is designed to achieve BREEAM excellent and WELL Gold certifications. An EPC B rating has been calculated.
The building design lowers operational carbon through the application of the Greater London Authority’s energy hierarchy: Be Lean, Be Clean, Be Green, Be Seen.
Be Lean: thermally efficient façades optimise the proportion of glazing to solid walls to give good daylight without unwanted solar gains. The new elevations in a white Roman brick and Portland Stone provide deep reveals to inset glazing, assisting in passive shading. Good daylight is achieved even for the deeper, lower, floors through generous ceiling heights.
Be Clean: the environmental systems marry operational energy efficiency with high standards of wellbeing. Openable panels on the façade allow natural ventilation and mixed-mode in mid-season. A quiet displacement system delivers generous air volumes through the floor.
Be Green: Air source heat-pumps and photovoltaics to make a renewable contribution.
Be Seen: the building integrates sophisticated sensors and controls. Spaces that are not occupied are not cooled, ventilated or lit. Conversely, spaces with higher occupancy levels are provided with additional ventilation and cooling.
Were the planners supportive of the proposals?
The planners were very supportive of the proposals. Three aspects were singled out for particular support: the scheme optimises the development potential of a well-connected site, enhances the public realm by introducing new permeability to Kensington High Street Underground Station and increasing the proportion of active frontage, and the quality of the new building design. The site is sensitive. It is surrounded on three sides by conservation areas and to the west the Grade II*-listed Derry and Toms department store and beyond it the Grade II-listed Barkers. We explored how the refurbishment should relate to these fine neighbours with their robust Portland Stone elevations and decorative bronze glazed infills. Elevations of white flush pointed Roman brick and stone were developed. Tonally they relate to the Portland stone, but the materiality of the brick establishes a subservient presence (and a relationship to the brick mansion blocks on the west of the site).
Is your approach to retrofit and the way you talk about it with clients changing, especially given the increased focus on the climate emergency?
Retrofit is often the right answer and hopefully The Kensington Building demonstrates that we have the expertise to refurbish buildings will care and commitment.
We do not believe, however, that retrofit is the right answer in every circumstance. Where existing buildings are compromised in their layout, structure or construction their retention may lead to very poor long-term results both in terms of building function and sustainability.
Our approach is, therefore, contextually driven and in no case would we presume to know the correct answer without a thorough understanding of the constraints and opportunities of the existing building.