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Wednesday23 July 2014

Bermondsey Island housing by Urban Salon

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By adopting two contrasting facade treatments, Urban Salon’s Bermondsey Island housing deftly negotiates the conflicting demands of noisy roads, sustainability requirements and a sensitive historic site.

The envelope of a building is part of the topography of the street, and the street is part of the landscape of the city. Negotiating the contours between them is a vital part of good inner city architecture.

Urban Salon’s recently completed social housing scheme, Bermondsey Island, provides a case study of the variety of ways this can be done successfully — including material and opacity variations, landscape detailing, colour differences and changes in use.

Located at the intersection of south-east London’s Tower Bridge Road, Long Lane and Abbey Street, the building lies directly over a scheduled ancient monument — the site of the former Bermondsey Abbey, built in the 11th century.

The archaeological value of the site was another reason for the careful consideration of how the building meets the street. Before the technical challenges began, however, the ideas of local residents helped to get this project off the ground.

Bermondsey Island site plan

SITE PLAN

1 Bermondsey Island affordable housing
2 Bermondsey Square development
3 Bermondsey Square

Urban Salon won the competition in 2003 with a diagram that demonstrated that the practice could maximise the development potential, thanks to its understanding of both the site and wider neighbourhood. Consultation with the locals in the adjacent pub brought about the call for a local bingo hall and, combined with a conviction to raise the living accommodation clear of the pavement, the submission proposed to lift the flats above the street and then manipulate the form to respond to the different environments on each side of the block.

Two of the four sides responded to the busy junction with a heavyweight, closed facade, allowing the remaining faces to display a more open, lightweight appearance.

The finished building remains faithful, in form and strategy, to that original competition sketch. There are a total of 13 flats spread over the five upper floors, supporting storage/plant space and a commercial unit (94sq m) on the ground floor.

The first four storeys rise up in the same form as the site, maximising the footprint, with the top two storeys and solar panel covered roof stepped back to prevent too much overshadowing to the surrounding streets.

 

 

Bermondsey Island cladding

Source: Gareth Gardner

View from Tower Bridge Road.

A natural solution to the heavyweight facade might have been brick. However, with the building hard up against the pavement, the prospect of long-term maintenance to pointing over public areas resulted in the use of a product that removed this altogether.
Two facades of the building are covered with Tilebrick cladding. This is a clay product, designed to mimic the appearance of traditional tile hanging while laid as a solid brick, with similar dimensions (168 x 102.5 x 102.5mm).

It features an overlapping lip, which avoids the need for horizontal pointing, and is laid without mortar between the perpends to create a tile-hung appearance.

Tilebrick is available in sandfaced or smooth finish in six colours, and the Bermondsey Island project uses a smooth blue to form the outer leaf of the facade. This is tied to a steel support system between concrete floors. The manufacturer also supplied specials, pre-cut off site, to reduce waste and improve the finish quality of the corners. However, the demands of the mortarless perpends and recommended 1mm joint reduced the ability of the contractor to adjust slightly between openings and some site cuts were still required.

Using the tile instead of brick meant a richness of texture and shadow could be better achieved, along with an interesting association with a well understood domestic vernacular, without the dangers from wind or impact damage inherent in a standard tile-hung detail. Relying on this richness, the scheme presented to the planning department proposed that the facades nearest to Tower Bridge Road be clad entirely in Tilebrick, and the opposite faces rendered in white.

The submission was one of the earliest cases to be commented on by the newly formed design review panel at Southwark Council. Urban Salon’s director Alex Mowat recalls that the proposal to allow the Tilebrick to meet the ground caused some concern. The panel initially wanted the base to be entirely glazed, but support from one of the panel members helped to persuade the rest of the committee to approve the design unaltered.

 

Bermondsey Island detail section

DETAIL SECTION

Another important factor in ensuring that the project remained as drawn from planning to tender and construction was the decision to complete drawing packages for stages E and F before awarding the design and build contract. A schedule of specials and cut bricks for each of the different angled corners was prepared as part of the tender information.

Developer Igloo novated Urban Salon to the winning contractor, Allenbuild SE, and this continuity of the design team was undoubtedly a key part of the successful delivery of the envelope as originally envisaged.

As a social housing scheme supported by funding from the Homes & Communities Agency, the design also had to meet the necessary criteria of the housing quality indicators system, Lifetime Homes and Code for Sustainable Homes.

The project achieves Code Level 4, assisted in part by the extensive photovoltaic solar panel array on the roof, which was required not only for the emissions improvement over building regulations, but also to meet Southwark’s demand for 20% carbon savings as a planning condition.

Delivering enough surface area to meet this proved challenging and the architects explored various configurations before ultimately settling for a single horizontal plane with each panel mounted on stands to achieve the optimum pitch.

The maintenance access areas of the roof, as well as the balcony decks serving the apartments, were covered in Ecodeck, a recycled plastic alternative to timber. The reduction in movement and warping in comparison to a traditional timber product was welcomed.

The archaeological value of the site demanded careful foundation design, transferring the load away from the edges towards the central core and carefully placed columns. Reducing the weight of the facade assisted this process. The second problem concerned site constraints and buildability. Using a masonry construction for both leaves of the facade would have resulted in a greater quantity of material, which would have been difficult to store on the tight site adjacent to the public highway. The contractor recommended the use of a lightweight steel system instead.

Tilebrick at Bermondsey Island

Tilebrick cladding at Bermondsey Island.

As the original competition sketch had predicted, the envelope’s role in protecting the inhabitants from the noise of the city played a key part in all aspects of the detailing and product choices.

Although the front and rear of the building display two very different surface finishes – one shielded by masonry, the other rendered white like its interior – the differences are only visual and psychological, as the same level of sound reduction had to be achieved throughout. This required taking into account acoustic issues such as avoiding resonance (and with it the danger of amplification) across insulation products of matching depth within the cavity or lightweight steel cladding that supported the Tilebrick and render.

The close proximity of the noisy traffic also had an impact on the ventilation strategy. Choosing background ventilation with extract meant the need for a number of outlets, each requiring an acoustic baffle and careful siting. In places they could be concealed in soffits or within the window frame, but in others the rendered surface had to be broken.

Both the visual and technical impact of the individual extract system suggests this was perhaps a good candidate for a centralised solution that could have also capitalised on heat recovery. The composite windows, top-hung due to the weight of the glazed unit used to achieve the sound reduction, were provided by Krone in grey and white for the two differently coloured sides of the building.

So, how successfully does the building’s envelope meet the city’s landscape? In the full-height glazed entrance facing Abbey Street the residents collect their mail in the pavement slab covered foyer before entering the private stair in the centre of the plan, protected from the pavement by the reassuringly tough brick core.

To the south, the building opens its ground floor again with the glazed commercial facade looking across at the site of the now demolished pub where once the call for bingo set this project on its way.

Building envelopes that meet the street entirely with glazing can too often result in only a forest of reflections and wayfinding confusion. Bermondsey Island proves that the way to avoid this is to choose your moments. The masonry cladding helps this building to firmly inhabit the site, the robust material protects the commodity and the finished surface is a delight.

Bermondsey Island section

SECTION

1 Tilebrick facade
2 Rendered facade
3 Photovoltaic panels
4 Krone double-glazed windows
5 Private terrace with planter
6 Powder-coated balustrades
7 Tilebrick to ground floor
8 Plant room
9 Refuse store

 

PROJECT TEAM

Architect Urban Salon Architects, Client Igloo Regeneration, Employer’s agent Keytask Management, RSL Hexagon Housing Association, RSL’s agent Potter Raper Partnership, Structural engineer Heyne Tillett Steel, M&E engineer BSEC Design, Acoustics consultant Cass Allen Associates, Contractor Allenbuild South East

SUPPLIERS

Tilebrick Ibstock, Render PermaRock, Windows Krone, Metal brick supports Wincro Metal Industries, Balcony balustrades Allied Fabrications

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