Apparata Architects’ affordable housing block in Barking provides 12 spacious, flexible homes – using 20% less embodied carbon than the RIBA 2030 target. Pamela Buxton finds out how it was done
“It’s working really, really hard. That’s why it’s in the building – it’s doing so much,” says Nicholas Lobo Brennan, co-founder of Apparata Architects, of the concrete that forms the distinctive aesthetic, and so much more, of A House for Artists, its affordable housing development in central Barking.
Not only is the in-situ concrete both the structure and external skin, it is central to the thermal, acoustic and fire performance of the building, which provides 12 homes for artists and their families above a ground floor community and events space. Its sustainability credentials are food for thought for those who may instinctively doubt the wisdom of using so much – the building’s embodied carbon is 470kgCO2eq/m², over 20% less than that targeted in the RIBA 2030 Climate Challenge. This was achieved by using high rates of cement replacement (50% GGBS above ground and 70% below), keeping build-ups lean and reducing the quantity of walls on plan, as well as minimising the surface area of thermal enclosure to give a very compact heated volume.
Commissioned by the London Borough of Barking & Dagenham and Create London, the housing is notable not only for its powerful appearance but for its built-in potential for configuration, and for its association with artist Grayson Perry, who has been its brand ambassador. The development provides four floors of dual-aspect apartments – including a co-housing second floor level – each accessed off a sheltered external walkway. Rather than fixed layouts based on outdated nuclear family norms, the practice wanted to make them as adaptable as possible. Key to this was the open-air escape strategy, devised in collaboration with fire consultant Menzies Consultants. This placed external escape routes at the front and back of the homes, enabling the architects to avoid space-hungry interior corridors and providing maximum flexibility.
The result is an efficient layout that allows residents to remove or add partition walls as required and, even more radically, to switch an unwanted bedroom to a neighbouring apartment via the use of “soft spots” in the party walls. On the co-housing floor, double doors in the living rooms can be opened up to allow access to the neighbouring apartments if and when desired: potential scenarios include elderly parents or extended family living adjacently. There are eight standard two-bed units plus four variations – including a double-height studio space – to the south-west. Floor-to-ceiling heights of 2.8m and full-height glazing enable high levels of light with privacy achieved by the setback facades.
Apparata wanted the housing to have the feel of a public building with a clearly legible structure of stacked elements, but with playful large circular windows and triangular forms. When the architects won the project back in 2016, it was to be a timber structure with precast concrete panels. That changed in light of the rising cost of timber and the Grenfell fire, as well as the IPCC’s special report on global warming. “We needed another strategy, and simultaneously sought to reduce material,” says Apparata co-founder Astrid Smitham. “Rather than have a structural concrete or steel frame combined with precast concrete panels (or another heavy facade material), we found that using one material to perform multiple functions was more effective. It meant a certain leanness was possible. Passive cooling was a consideration too, particularly in comparison to steel.”
They also reduced materials by removing canopies, which meant less concrete was needed in the ground-floor columns.
The total wall build-up is approximately 500mm, including the insulation (see diagram). Thermal bridging was dealt with using thermal connectors. “It’s worth pointing out that the thermal connectors are not used as cantilevers, which is more common,” says Smitham. “The walls were cast in two parts, a lower part incorporating the thermal connector, then slab, then the upper part of the wall up to soffit. The sequencing made construction on-site easier and also created the facade pattern of a continuous horizontal band.”
The build took 15 months. To realise the concrete, Apparata worked closely with both contractor Murphy and subcontractor Togher Construction. This relationship was vital according to Smitham, with the architects participating in workshops and working with the PERI Trio formwork system to draw the facades and agree both the optimum layout of formwork and the sequencing of pours. For the horizontal bands, for example, the use of smaller formwork panels worked well architecturally and also technically in relation to the 925mm fire resistant upstand, which runs between all the floors along the external walkways. “The final outcome is an expression of the architectural stacking, but also of construction practicality,” says Smitham.
In order to reduce site waste, unlined standard reusable formwork was used. The architects were keen to use as much secondary cementitious material as possible to reduce the carbon footprint of the concrete, and also to achieve a lighter coloured finish. They compared the appearance of different mixes – 40% and 50% GGBS, against 100% Portland cement – using large-scale 2.5m x 2.5m mock-ups, created nearby before being moved to site. In particular, they were concerned that the longer curing time required for high proportions of cement replacement might lead to more pronounced marking (it didn’t).
A second test panel was made on-site to test corner formwork and rebar options, and slab/wall joints. A Sika surface coating was applied to protect against staining, for aesthetics and long-term maintenance, and the sloping concrete parapets were detailed to ensure that water drains inwards into the walkway/roof drainage and away from the facade.
Inside, concrete soffits are exposed to maximise the thermal mass and so reduce overheating. The floors are raised with acoustic cradles (see diagram). Partition walls can be easily removed to change the layout, giving flexibility not only for its use as housing but for future uses. Even though it was designed pre-pandemic, the architects observe that it is actually “perfect Covid” housing, due to its cross-ventilation, sheltered outside spaces, flexibility, and potential for forming a bubble with neighbours.
A House for Artists is expected to be fully occupied by spring and is the practice’s largest built project so far. It will be fascinating so see how its potential for flexibility is embraced by its occupants over time.