The Vibe, East London

The Vibe is an unusual and innovatively-designed residential scheme in fashionable Dalston, east London, where precast cladding is one of the signature features of the building envelope.

Telford Homes is developer for the site, which comprises 101 one-, two- and three-bed apartments over seven storeys, above a two-form entry primary school for 420 pupils. Not only was this a clever use of limited space, the homes cross-subsidised 100% of the school construction costs, offering a possible template for mixed-use development on other small urban sites.

The Holy Trinity Primary School is set out over the lower three levels of the development. The cores of the reinforced concrete frame for the 9,550 sqm residential building above were positioned at the north and south ends, to avoid disrupting circulation in the school below.

The scheme was designed and taken through planning by Rock Townsend architects, with Stockwool providing the detailed design and material specification – including selection of precast specialist Decomo for the cladding package.

On such a tight site, precast was an obvious choice for elements of the envelope, given the speed with which it could be erected. Decomo supplied around 400 reinforced concrete cladding panels, acid etched with a white ‘Portland stone effect’ finish, which sit in a mixed palette of materials, also including brick and glazing, selected to blend in with the local built environment. The cladding has mostly been used on the upper residential storeys, except for the two ends, where it also features on the lower, school levels.

The apartments featured steel bolt-on balconies, which meant complex interfaces and fixings with the cladding panels. “Decomo created a full mock-up in its factory, in collaboration with Stockwool and other suppliers, to show how the different elements would fit together,” explains Wilf Sinclair, project architect with Stockwool. “This gave us assurance about the build quality. Decomo was capable of casting a very slim precast panel, which could fit in behind the steel balcony.”

Decomo also worked closely with Stockwool on bespoke elements of the precast package. “Above the head of the windows, where the precast panels form a continuous band, there were no zones for the ventilation ducts,” says Sinclair. “The solution was to create slots in the precast panels, and cast in the plenum boxes and spigots behind, which connected up to the ventilation duct. It was a neat detail which meant the ventilation penetrations were very discrete.”

Although the scheme was largely designed in 2D, the precast elements were 3D modelled by Decomo. “Most of the panels were bespoke, and we created 3D models of them, which we then sent across to Stockwool so they could understand how all the different sections fitted together,” explains Decomo’s project manager on The Vibe, Dave Dewsbury.

With so little repeatability, this meant casting the panels in the factory was “quite tricky”, Dewsbury adds. “We had to adapt the mould differently for almost every panel, starting with the largest, and then gradually reducing the size of the mould as we worked down through the section sizes,” he says.

The weights of the panels varied from around 700kg up to 6.3 tonnes. The fa├žade design philosophy was to keep the elevations as clean as possible, with minimal jointing, and the largest sections were on the eastern elevation. “Here, because the architect was reluctant to split the panels, we hired a special seven-axle mobile crane from Spierings, as these sections were outside the tower crane’s capacity,” explains Dewsbury.

On the western elevation, on the top levels, there is a colonnade feature which required some ingenious temporary propping. “The colonnade comprises four columns, which sit on the structure’s core wall,” says Dewsbury. “These sections had to be temporarily propped, to provide stability, then fixed back into the structure and fully grouted to the concrete frame behind.” Halfen FPA precast panel anchors were used for fixing the panels.

Another challenge was the installation of six units above the school playground area at the north and south ends on the western side of the development. “The cladding panels were returning to the underside of the soffit, and because they couldn’t be installed from below, they had to be ‘underslung’,” Dewsbury explains.

“Decomo’s panels ticked all the boxes in terms of appearance, creating the desired Portland Stone effect, which shows up well in the sunlight,” says Sinclair. “We were very satisfied with the construction quality.”

The clever design of the Vibe project made it a winner at last year’s Housing Design Awards, while the school below took the education category at the Architects Journal Awards.