Fancy façade

Clay Technology magazine
,
15 Feb 2018

Cartwright Gardens is located in the middle of central London, surrounded by a Georgian garden square. Opposite sits a newly built student hall featuring a 4,500m2 brick façade that was delivered using off-site construction. Ines Nastali reports. 

When it comes to student halls, most of us probably have images of tiny bedrooms, crammed shelves and a lack of heating and insulation in mind. However, the new £140m University of London Garden Halls accomodation, located in London’s Bloomsbury conservation area, framed by opulent town houses, has nothing in common with such images. Instead, it features cinema rooms, tennis courts and landscaped gardens.  

The nine-storey facility accommodates 1,200 student rooms while a seven-storey self-catered block fronting a neighbouring street replaced outdated 1930s and 1950s buildings. These were demolished while another tower, stemming from the 1960s, was stripped back to its concrete core and also furnished with a brick façade to fit the concept – to create a unified assembly. Planning permission for a building of similar height might have not been granted if the original 13-storey tower was demolished.

This approach also helped the development achieve ‘a BREEAM New Construction 2011 excellent rating, the second highest, with a final score of 73.1%. Sustainable features include photovoltaic panels on the roof, a number of green roofs, low flow taps and sanitary fittings,’ states construction consultancy McBains, which was contracted with project management for the newbuild by The University Partnership Programme, responsible for the execution of the refurbishment. 

BREEAM, the Building Research Establishment’s Environmental Assessment Method, is a sustainability rating scheme developed by the Building Research Establishment, a science centre comprising researchers, scientists and engineers based in the UK.

Their rating considers the impact of construction and reduction of emissions, water consumption, materials use and waste. The excellent rating puts the Garden Halls among the top 10 new non-domestic buildings that have been accredited by the scheme.

Plan the delivery

The programme chose TP Bennet as executive architects for the redevelopment of the halls, while Maccreanor Lavington architects were commissioned to work on the brick façade.

‘The site is surrounded by numerous listed buildings and sits within the Bloomsbury Conservation Area. English Heritage, Greater London Authority, Camden Borough, Bloomsbury Conservation Area Advisory Committee, 20th century Society and the Georgian Society are some of the key local stakeholders that we have consulted through the development of the design,’ Maccreanor Lavington states in a project report. In addition to the BREEAM rating, ‘the scheme is designed to meet the Mayor of London’s sustainability standards’.

Maccreanor Lavington had to consider two things to keep constructional impact low – how to fit the façade’s design into the historical built environment and how to tackle the construction of the refurbishment with minimal disruption.

Go for brick

Considering these challenges, the choice for the façade’s material fell on brick, having also considered using Portland stone. ‘We love brick,’ Gavin Finnan, Associate Director at Maccreanor Lavington tells Clay Technology. ‘For many reasons, such as its variety, texture, and quality. It is robust and lasts a long time and is a permanent and solid material choice,’ he says. Bricks were supplied by Danish company Petersen, who fired up the coal kiln to produce buff water struck bricks. Normally, bricks only have one good side, when cut in half, but the Petersens comes with two good faces and both halves were used – one example of reducing the use of materials.

‘The design takes its cues from the larger Victorian and Edwardian buildings that have been previously added to the fabric of Bloomsbury,’ it is stated in Maccreanor Lavington’s project report, addingt that, ‘The Petersen brick is the principal building material chosen for the elevation. 

This is offset by white reconstituted stone and glazed terracotta sills and a two-storey mansard built from Portland stone. The upper five storeys are expressed as a series of stepped brick piers and frames over various window openings that are gathered together to form a vertical order over the façade.’

The Leigh Street corner building is expressed as a pair of simple punched brick elevations. Darker water struck bricks are used here to match the soot-aged look of the neighbouring area. The windows have reconstituted stone surrounds and the brick sits on a single storey stone base evoking the memory of the 1950s buildings that went before.

Off-site duty

The decision to use brick also made off-site construction of the elements possible, so that there was no long lasting disruption to the lives of Cartwright Garden residents caused by the construction and scaffolding and there was no additional long-term strain to the traffic. Thorp Precast, based in Staffordshire in the UK, was tasked with building three storey façade elements using a precast system.

‘The entire 4,500m2 brick façade was manufactured off-site as brick faced precast concrete panels. The prefabrication allowed the design team to develop stepped brick details that make reference to the detailing of traditional load bearing masonry. The depth of the façade made it possible to construct the façade from large load bearing units, which require fewer movement joints than contemporary site laid brick cladding,’ Maccreanor Lavington stated in a press release, adding, ‘This leads to a building with a more monolithic character akin to traditional masonry while minimising the amount of on site labour. The overall development was delivered to budget within a tight 26 month programme.’

Time was also another reason for choosing off-site construction. The student halls had to open in time for the new term start in September, while the amount of stepping in the elevation slows the crafting down as ‘assembling this kind of façade is very difficult, there are different skills required as it is a heritage project,’ Finnan states. 

‘The main elevation consists of a series of U-shaped brick faced mullions up to the second floor, following by a series of triple and double storey T-shaped recessed units. These were infilled with smaller spandrels to form the window openings,’ Thorp Precast states.

‘At the top of this elevation are a series of set-back mansard dormers that have reconstituted stone wings and terracotta facings. A dormer consisted of two wings and a lid, which included some tricky geometry. 

The whole job was stacked, meaning only restraint was taken off the primary structure with all the load going into the foundations.’

Deliver the brick 

This stress shifting was achieved through above-mentioned T-shaped units and piers. ‘These were stacked on top of each other and fixed to the concrete frame of the cast. The sills were then bolted to the piers on one side,’ Finnan states. This way, the reinforced concrete cast only has to bear the horizontal weight of the bricks and of the two-storey mansard, which meant less concrete was needed than if it had to support the weight of the precast panels.

After a full mock up was delivered to the site for testing and adjustment, the panels were put in place using a crane. ‘There are approximately 1,100 precast panels incorporating four brick types on the project. The installation had to be done in a very condensed period of time and in order to meet the targets we used three gangs on site working on separate tower cranes,’ Thorp states, adding that, ‘Being a central London project, space was at a premium and we had to work within strict road closure times, all of which added to the challenge. 

‘The facade was built in three zones,’ Finnan explains, adding that work began in the north end. 

In each zone, the lower three-storey piers were erected first, followed by spandrels and sills being slotted in. This process was repeated up the full height of the building with three-storey T-sections followed by two-storey T-sections. The mansard sections were lifted into place together with the two-storey dormer windows.’ Thorp adds, ‘When it came to the finishing, access was non-existent, so we employed three teams of abseilers to carry out the works.’

The accolade

After construction had finished, the project received a wealth of nominations, commendations and one award for the façade, the execution of the off-site construction and its architectural worth in general.

Richard Lavington, Founding Director of Maccreanor Lavington, summarises what, to him, is special about the building. ‘The depth of the facade allows for the modelling of light and shade appropriate to a building of this scale. The unique Danish brick combines references to the warm pale hues of Portland stone and the texture of the surrounding Georgian brickwork, which the shadows of the grand London Plane trees within the garden can play. The brass and stone of the entrance reference those of 19th century buildings with the hues of the stone reflecting the shades of autumn leaves within the square.’