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Wednesday30 July 2014

Great Suffolk Street student housing by Allies & Morrison

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Allies & Morrison’s student accommodation buildings in Southwark met the challenge of mixing modular construction with traditional brickwork.

Brick has good credentials to be considered as the first modular material – produced off site, in elements of regular size and appearance, and assembled in a systematic way to create a larger structure. But marrying this mat-erial with a more contemporary approach to modularity on a project presented Allies & Morrison Architects with challenges that it could only overcome through rigorous quality control and with the assistance of a dedicated subcontractor.

It is fortunate then that the project is just round the corner from the practice’s office in central London. The development, at Great Suffolk Street, in Southwark, is of student housing for Unite Group, the UK’s leading provider of such accommodation. One of the contributors to Unite’s success is its use of prefabricated modules, which it manufactures in its own factory in Stroud, Gloucestershire. Combining this approach with the use of brick created the project’s main challenge.

Allies & Morrison chose to use brick on the lower of the two buildings it has designed for Unite, which sits on the Great Suffolk Street frontage. Set between railway stations that include London Bridge and Waterloo, it is a street that gains much of its character from the viaducts that cross it, and the railway arches that are tucked behind it. All these structures are in London stock brick, darkened with age and pollution.

The site itself had a history as a pottery but had long been empty. Allies & Morrison came up with a scheme that provided rooms for 230 students, in a long slim six-storey building fronting the street, and a 13-storey block behind. The two are linked by a courtyard and a podium that has a green roof at first floor level.

It was granted planning permission for the site in August 2008, with a third building also on the site, a proposed office to the north. Unite has chosen not to develop it, and has sold the plot for potential use as a hotel.

The plan was always to open the accommodation to students in autumn 2010, so there was a scant two years for detailed design and construction. The lower block uses Unite’s prefabricated units which can provide either single study bedrooms in a multi-person flat or, where two units are combined, a studio apartment.

The units are of precast concrete. They sit on a raised slab but then are self-supporting, needing no additional structure. With a corridor running the length of the building, units are arranged perpendicular to it at the front, and parallel to it at the back.

On the tower, however, using these modules was not an option. The company had previously built to 11 storeys high, but this building was two storeys higher, and with a relatively narrow footprint. So the architect used conventional construction, of in-situ reinforced concrete, and concentrated the larger units within the tower.

The lower building envelope

Prefabrication of the bedroom units made the use of brick-work on the lower building possible. Since all the units were erected in just three weeks, more time could be spent on the cladding.

“We wanted something to address the street and at a human scale,” says project architect Yasmeen Shami. Brick is used widely on the street, both on old structures and on a recent building by Panter Hudspith Architects.

The architect created a framework of shallow brick piers and spandrels, which are three bricks deep and enclose an anodised aluminium rainscreen around the windows.

To ensure the structural stability of its prefabricated units, Unite has strict requirements in terms of the positioning and size of the windows. Here they are as large as possible.

The rainscreen consists of three elements: a flat panel below the window, a narrow grille that contains the opening of the window for security reasons, and a larger panel that angles out 15 degrees in the horizontal plane.

The architect wanted to use a London stock brick that was yellow, but not too glaringly so. It settled on a Danehill yellow, which has a nice degree of variation. The greatest difficulty came from the fact that the modular units are not built to a brick dimension, and from the tolerances which proved greater than the architect had been led to expect.

The piers are very narrow, just two bricks wide, so all the tolerances had to be accommodated in the spandrels. “Mansell [the contractor] were brilliant,” says Shami. “They built mock-ups on site, one just for the brickwork, and one for a complete bay.” Tolerances in the units, which were supposed to be 5mm, turned out to be 20mm. This was taken up in the joints of the rainscreen, and the mortar widths in the brickwork were used to accommodate the non-standard dimensions.

The tower envelope

The tower is entirely clad in anodised aluminium, with panels and windows used in a chequer-board pattern, which only varies at the very top to create a castellated effect. Technically this was more straightforward than the lower block, as it needed to be, since the use of conventional construction did not allow so much time to be dedicated to the cladding.

The main challenge came in the layout of the apartments which had to be reversed from one floor to the next, to accommodate the chequerboard glazing. There are some noticeably darker cladding panels towards the top of the building, but Yasmeen Shami says that colour variation in the panels is common in the anodising process and all the panels are within the allowed tolerances.

Project team

Architect Allies & Morrison, Client Unite Group, Contractor Mansell, Structural engineer Waterman Structures, Building services engineer Waterman Building Services, Acoustic consultant Sandy Brown Associates, Concrete frame/groundworks Atlantic Contracts, Cladding (Tower) McMullen Architectural Systems; (lower building) Topek, Bricks Grangewood Brickwork Services, Render Conneely Drylining, Metalwork Thames Valley Fabrications

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Readers' comments (2)

  • “We wanted something to address the street and at a human scale,” says project architect Yasmeen Shami.....

    oh dear

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  • Please note that the volumetric Modules supplied by Unite Modular Solutions on the Great Suffolk Street Student Accommodation scheme were of lightweight steel construction - not precast concrete as erroneously stated in the above article.

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